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ABSTRACT
THE INCIDENCE AND CHARACTERISTICS
OF NEOPLASMS IN CATS

by Robert E. Schmidt

This thesis is a study of 256 neoplasms of cats in the Michigan State
University, Department of Pathology, collection. Emphasis was placed on
sex and age incidence of the cats. A complete histologic description.was
given for each tumor type.

The average age of cats in this study was 7.9 years. Ninety-one
males and 110 females were affected. Classifying the tumors on the basis
of cell of origin, 33 different tumor types were studied. The majority of
the tumors (72%) was malignant, with mesenchymal tumors being more preva-
lent than epithelial tumors.

Malignant lymphoma was the most common type, and was considered to
be the most significant tumor of cats. Tumors of fibrous tissue comprised
the 2nd largest group, and this was the only group in‘which there'were more
of the benign than the malignant type. Mamary gland tumors were 3rd in
occurrence, and included 1 mixed mammary tumor. This tumor is apparently
very rare in cats, as no reports of its occurrence could be found. The
4th largest group was the squamous cell carcinoma. These tumors occurred
primarily in the oral cavity and the skin of the head.

In contrast to some reports, the mastocytomm was a frequently occurring
neoplasm, making up 52 of the total number. The basal cell carcinoma had a

histologic pattern of cells arranged in small islands which resembled

THE INCIDENCE AND CHARACTERISTICS

OF NEOPLASMS IN CATS

By

Robert E. Schmidt

A.THESIS

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

MASTER OF SCIENCE

Department of Pathology

1966

ACKNCNLEDGEMENTS

The author would like to express his appreciation to the following:

To Dr. R. F. Iangham, major professor, for his personal enthusiasm
and interest in this project, and for the many hours of guidance and
teaching which were so necessary for its successful completion.

To Dr. S. D. Sleight, whose assistance and advice on scientific
writing and thesis preparation have been greatly appreciated.

To Dr. G. L. Waxler, for his time in reading the manuscript and
making many helpful suggestions, and for time spent explaining the intri-
cacies of photomicrography.

To the histotechnicians of the Department of Pathology, and especially
Mrs. Mae Sunderlin, who spent many hours doing the special stain techniques
used in this study.

To the Air Force Institute of Technology, Air University, United
States Air Force, who made this year of study possible.

Finally, to my wife Sylvia, who has endured much during a difficult
year. Her constant support and encouragement have been a great help to

me, and I am deeply grateful.

ii

TABLE OF CONTENTS

ImmmIONO O O O O O O O O O O O O O O O

REVIEWOFLHERATURE............

A.

B.

General Articles . . . . . . . .

Tumors of the Skin and Subcutis.

Tumors of Bone and Cartilage . .

Tumors of

Tumors of

Tumors of

Tumors of

Tumors of the Nervous System . .

Miscellaneous Tumors . . . . . .

AND mnms O O O O O O O O O O 0

General.

Specific

DISCUSSION. . . . .

A.

B.

General.

Specific

Tumor Types . . . . . .

O O O O O O O O O O O 0

Tumor Types 0 s e o e 0

SUMMARY AND CONCLUSIONS . . . . . . . . . .

LISTCFREFERENCES.............

VITA. O O O O O O O O O O C O O O O O O O 0

iii

the Vascular, HemOpoietic,

and

the Respiratory SYBtem e e e e

the Alimentary Tract and Liver

Lymphoid Tissues.

O O O O O

the Urogenital System and luminary Gland.

O

Page

10
11
12
12
18
58
58
59
66
68

73

LIST (I TABLES
Table Page
1 Age and sex incidence of each tumor type. . . . . . . . . . . . 14
2 Tuoralistadbytypaoftissua.............,,.17

3 Site of involvement in malignant lymphua . . . . a . c 9 9 v o 59

iv

Figure

10

11

12

13

14

LIST OF FIGURES

Age distribution of cats with neoplasms. . . . . . . . . . .

Basal cell carcinoma. Small nests of cells separated by
delicate stroma. . . . . . . . . . . . . . . . . . . . . . .

Basal cell carcinoma. Note nests of cells that resemble
tubules, with peripheral cells arranged perpendicularly to
the basement membrane. . . . . . . . . . . . . . . . . . . .

Basal cell carcinoma. Abrupt transition from normal to
neoplastic epithelium. Some small cellular nests can be

.3.“ O O O O O O O O O O O O O O O O O O O O O O O O O O O C

Squamous cell carcinoma. Note nucleoli, tonofibrils, and
dense collagenous stroma . . . . . . . . . . . . . . . . . .

Melanoma. Concentration of pigment carrying cells in the
basal epithelium. Note enlarged nucleoli of the neoplastic

cell.‘ 0 O O O O O O O O O O O O O O O O O O O D O 0 9 O O .

Adnexal carcinoma. Small epithelial cells clustered around
the base of a hair follicle. . . . . . . . . . . . . . . . .

Sebaceous adenoma. Enlarged sebaceous cells with hyper-
Chrmt 1C nuc 1e 1 e O O O O O O O I O O O O O O O O O O O O O

Ceruminous gland adenocarcinoma. Note large nucleoli and
prominent inflammatory reaction. . . . . . . . . . . . . . .

"Solid" type mamary adenocarcinoma. . . . . . . . . . . . .

Mammary adenocarcinoma. Vesicular nuclei.with prominent
nucleoli. Cells have formed fairly well differentiated

ac 1111. O O O O O O O O O O O O O O O O O O O O O 0 O O O O O

mammary adenocarcinoma. Cystic acinus with papillary pro-
jCCtions into the lmnO O O O O O O O O O I O O O O O O O O

Mammary adenocarcinoma. ‘Metastatic lesion in pituitary.
Pleomorphic cells which have formed acinar structures. . . .

Hepatocarcinoma. Metastatic lesion in the spleen. The
neoplastic cells have large vesicular nuclei with promi-
nent nuc 1e 011. O 0 O O 0 O O O O O O O O O O O O O O O O a O

Page
13

19

19

20

20

23

23

24

24

27

27

28

28

31

Figure

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16

17

19

20

21

22

23

24

25

26

27

28

29

30

31

32

Pancreatic adenocarcinoma. Implanted lesion in wall of
the intestine. Note the occurrence of zymogen granules
in several of the neOplastic cells . . . . . . . . . . . . .

Intestinal adenocarcinoma. Neoplastic cells in the smooth
muscle. Some acini being formed . . . . . . . . . . . . . .

Mucous adenocarcinoma. Note large neoplastic cells with
fm cytOPMme O O O O O O O O O O C O O C O O C O C O O O

Adenocarcinoma in mesentery. Very anaplastic cells with
only slight tendency toward glandular formation. . . . . . .

Fibrosarcoma. Pleomorphic hyperchromatic nuclei, prominent
nucleoli and mitoses . . . . . . . . . . . . . . . . . . . .

Malignant mesenchymoma. Section of anaplastic fibrous
Clements With mitOtic figurel. a a a a a a a a a a a a a a a

‘Malignant mesenchymcma. Myxomatous tissue and bone. . . . .

Neurofibrosarcoma. Neoplastic cells which have apparently
originated from.a nerve bundle . . . . . . . . . . . . . . .

Myxoma. Scattered nuclei and abundant myxomatous ground
substance present. . . . . . . . . . . . . . . . . . . . . .

Meningioma. Whorling arrangement of degenerated neoplastic
cells‘which have undergone mineralization. . . . . . . . . .

leiomyosarcoma. Although the nuclei are pleomorphic, the
"twisted" appearance of several can be noted . . . . . . . .

Ieiomgoma. The tumor cells can be seen adjacent to the
walls Of the vessels 0 O O O O O O O O O O O O O O O O O O O

Rhabdomyosarcoma. Bizarre-shaped cells with faint cross
striations in the cytoplasm. . . . . . . . . . . . . . . . .

Lipoma. Fat cells separated by abundant collagenous

strm O O O O O O O O O O O O O O O O O O O O O O O O O O O

Chondrosarcoma. Abrupt change from anaplastic chondro-
blasts to more mature cartilage. . . . . . . . . . . . . . .

Osteogenic sarcoma. Stellate osteoblasts, osteoid, and
giant cell 0 O O O O O O O O O O O O O O O O O O O O O O 0 O

Hemangiosarcoma. Anaplastic endothelial cells around a
vasct‘lar space 0 O O O O O O O I O O O O O O O O O O O I O O

Mastocytoma. Metachromatic granules which have obscured
the nucleus in many of the neoplastic mast cells . . . . . .

vi

Page

31

33

33

35

35

37
37

39

39

41

41

42

42

44

45

45

48

Figure
33

34
35

36

37

38

39

40

41

42

43

45

Mastocytoma. Note loose, scattered arrangement of the '

mat ce 118 O O O O O O O O O I O O O O O O O O O O O O O O O

Malignant lymphoma, reticulum cell type, in the myocardium .

Malignant lymphoma, reticulum cell type, which has replaced

namelkidneyparenChYMaaeaaaaaeaaaeaaea

Malignant lymphoma. Annular thickening of small intestine
due to infiltration of lymphoid cells. . . . . . . . . . .

Malignant lymphoma, reticulum cell type. Note the extreme
variation in size of the cells . . . . . . . . . . . . . .

Malignant lymphoma, reticulum cell type. Note the reticu-
lar fibers around individual cells and small groups of
cells. The same tumor as Figure 37. . . . . . . . . . . .

Malignant lymphoma, reticulum cell type, which has infil-
trated the kidney. . . . . . . . . . . . . . . . . . . . .

Malignant lymphoma. Monotonous sheets of cells with loose
arrangement....................o...

Malignant lymphoma. Mbnotonous sheet of densely packed
cells. Compare with Figure 40 . . . . . . . . . . . . . .

Malignant lymphoma. Neoplastic cells which have isolated
and replaced normal liver parenchyma . . . . . . . . . . .

Malignant lymphoma. Neoplastic cells in skeletal muscle .

Mixed mammary tumor. Note glandular elements within
antacid material 0 O O O O O O O O O O O O 0 O O 0 O O O 0

Mixed mammary tumor. Higher magnification of Figure 44.
Note glandular acini within osteoid matrix . . . . . . . .

vii

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50

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55

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57

INTRODUCTION

neoplasia in cats has been recognized for some time, but has not been
considered an important field of study. Compared to reports dealing with
neoplasia in animals such as the dog, the literature concerning tumors in
cats is scanty, and only in recent years has there been much effort to study
feline naoplasma.

As late as 1957, Cotchin stated that little information was available
about the incidence of tumors in cats. Most reports fall into 2 cats-
gories: single case reports and reports of a series of tumors. The latter
usually concentrated on figures indicating age and sex incidence and classi-
fication of the tumors according to tissue of occurrence. Unfortunately,
most of these reports have little or no histologic description of the
neoplasms. ..

The objectives of this study of the tumors in the Michigan State Uni»
versity collection were as follows: (1) To tabulate the incidence of tumors
in cats with respect to age, sex, and cellof origin, and to compare these
figures with those reported in the literature. (2) To give a complete
description of the histologic features of each tumor type. (3) To discuss
the more important tumors occurring in cats, emphasizing the similarities

and differences as compared with neoplasms in other species.

REVIEW OF LITERATURE

A. General Articles

Crocker (1919) listed a series of 401 necropsies of cats, with only 4
tumors reported. Included were an osteosarcoma, a cavernous hemengioma of
the liver, and a fibroma of the cerebellum. No histologic description was
given, and the exact classification according to cell type cannot be criti-
cally reviewed. Feldman (1932) referred to the scarcity of reports per-
taining to the frequency of tumors in cats. He stated that in 1929 and 1930,
582 cats were treated at the New York State Veterinary College, only 1
having a tumor. Conclusions drawn by Feldman concerning feline neoplasms
were that they were not common in young cats, and that the most common
type was carcinoma. Mbrrill (1937) stated, "accurate data on the incidence
of tumors in cats are not available". He concluded that because of the
low economic and sentimental value of cats, many were not seen by veteri-
narians. In Morrill's series of 108 tumors, only 1 was from a cat, and it
was an adenocarcinoma of the mammary gland.

Lasserre, Lombard and Labatut (1943) reported on a series of 4496
cats they had examined. Of these, 46 (1%) had tumors. Twenty-three of
the tumors were adenocarcinomas of the mammary gland. Lombard (1943)
cited much of the earlier French literature to the effect that cancer in
cats was rare. Douglas (1951) said, "neOplasma were so rare in the cat
as compared with the dog, that it was not easy to describe any common
types". He further stated that epithelioma of the esophagus was the most

frequent neoplasm.of cats.

3

Mulligan (1951), in a series of 66 tumors in cats, found that more
occurred in females than in males, and that the squamous cell carcinoma was
the most cannon type. Plummer (1951) reported 2 feline tumors in a series
of 60 from domestic animals. These were an hemangioma, and an embryonal
nephroma. In 1956, Plummer reported a series of 636 tumors in domestic
animals with only 7 from cats. Two of the 7 were described as papillary
carcinomas of the mammary gland.

Cotchin (1951, 1952, 1956a, 1957, 1958b) reported on the incidence of
tmnors in cats as indicated by his series. The majority of the tumors
were either from the skin or the alimentary tract, with the next most com-
mon sites being the mammary gland and the lymphoid tissue. Alimentary
tract tumors were primarily squamous cell carcinomas of the upper tract,
and lymphosarcomas involving the intestine. Of interest in connection
with the high incidence of upper alimentary neoplasms was the observation
that the cat is the only species other than men in which spontaneous cancer
of the esophagus occurs comonly. Cotchin postulated that the cats might
be ingesting a carcinogenic agent. Cotchin did not report any tumors of
the central nervous system, but he stated that in most necropsies of cats
an examination of the nervous system was not done.

Cotchin's studies indicated that the majority of the tumors were from
male cats, and most were from older animals, with a peak incidence at 9
years of age. He postulated that the occurrence of tumors in older cats
might reflect the long latent period of carcinogenic action in some cases.
A tumor reported to be more peculiar to the cat than to other species was
the ceruminous gland tunor (Cotchin, 1961). No reasons for this occurrence
were given. In many of Cotchin's reports, little or no histologic descrip-

tion of tumor types was given.

J .

LA)

4
Smith and Jones (1961) listed a series of 8159 neOplasms of domestic
animals compiled from several sources. Only 174 of these were from cats,
with squamous and basal cell carcinoma of the skin, malignant lymphoma,
mamary adenocarcinoma, and squamous cell carcinoma of the esophagus being

reported most frequently.

B. Tuna-s of the Skin and Subcutis

Most of the reports which deal with tumors of the integument are cited
in section A. Squamous and basal cell carcinomas were listed most frequently.
Of special interest is the squamous cell carcinoma of the ear of white cats.
Moulton (1961) stated that there was a significantly high incidence of this
condition in California. Solar radiation was considered an etiologic factor.

Seawright and Grono (1964) and Meier (1957a) have reported cases of
cutaneous mastocytoma in the cat. The histologic description given in the
above cases was similar to that described in dogs, with cords of neoplastic
cells arranged in clusters and separated by delicate connective tissue.
In the case described by Seawright and Grono the tumor recurred after sur-
gery, and there were metastases to the regional lymph nodes, liver, and
spleen. The authors stated that the spleen is always involved in

mastocytoma.

C. Tumors of Bone and Cartilage

Reported tumors involving bone in cats have included a giant cell
tumor of the tibia (McClelland, 1941) and an osteoganic sarcoma (Purdy,
1961). In addition, Cotchin (1951, 1952, 1956a) listed tmors of the
skeletal system in several of his series. Barron and Saunders (1959)

reported the unusual case of a primary chondrosarcoma of the uveal tract.

D. Tumors of the Vascular, HemOpOietic, and Lymphoid Tissues

Lillie (1931) stated that reported cases of leukemia in the cat were
rare. He reported 1 case, with leukemia and splenic and hepatic involvement.
The neoplastic cells were described as having basophilic granules, and the
diagnosis was mast myelocyte leukemia.

Visceral lymphosarcoma appears to be peculiarly frequent in the cat
(Nielsen and Holzworth, 1953; Holzworth and Nielsen, 1955). The average
age of affected cats was 8 years, and the condition occurred more commonly
in males. The organs primarily affected were the small intestine, mesen-
teric lymph nodes, liver, and kidney. The intestinal lesion was usually an
annular enlargement*with occlusion of the intestinal lumen. Multicentric
origin of the neoplasm*was suggested in 5 cats with bilaterally affected
kidneys, although in most cases it was considered difficult to differentiate
between mmlticentric origin and true metastasis. The tumors were classi-
fied histologically as either lymphoblastic or lymphocytic lymphosarcoma.

Another common site of occurrence of visceral lymphosarcoma was the
pericardiac mediastinum. Holzworth (1958) considered the‘most frequent
cause of thoracic transudate in the cat to be lymphosarcoma arising in the
thymus or mediastinal lymph nodes. This neoplasm can occur in the thymus
of cats under 1 year of age as reported by Morgan (1959).

Two cases of intestinal lymphosarcoma in which surgical treatment
was attempted were reported by Patterson and Meier (1955). Multicentric
origin in Peyer's patches was suggested by the segmental distribution of
the lesions. Holzworth (1960) reported 155 cases of leukemic disorders of
cats. She stated that malignancies of the blood forming tissues were a

prominent cause of fatal illness in the cat. Holzworth's data indicated

7

In the report of Lebie and Fontaine (1960), as in the reports of Lillie
(1931) and Holzworth (1960), there appears to be a difference of terminology
regarding cases of basophilic granulocytic leukemia. Michele (1963) said
that in manuals the mast leukocyte is one of the granulocytes and has no
morphogenetic relationship to tissue mast cells. Boyd (1961) stated that
mast cells have no relation to the basophils of the blood. Moulton (1961)
described mastocytcma as occurring mostly in the dermis. However,

Selye (1965) stated, "it seems reasonable to assume that the blood
basOphil represents the circulating form of the mast cell system." It
is apparent that the question of relationship is far fraa settled.

Reports of tumors arising from cells of the blood vessels of cats are
rare. Houlton (1961) said that hemangiomas and hemangiosarcaaas have been
noted in cats, but apparently are not cos-on. The occurrence of an hemangio=
endothelioma at the base of the tongue was reported by Lombard (1964).
Hemangiopericytoma in a cat was reported by Damnert (1961). The tumor mass
occurred at the medial canthus of the left eye, and the ne0p1astic cells

formed whorls around the small vascular spaces within the tumor.

E. Tumors of the Respiratory System

Bronchogenic carcinoma in the cat has been reported by Troy (1955).
Primary alveolar carcinoma in a 13-year-old cat was reported by Sedlmeier
and Dahme (1958). Stflnzi (1958) discussed 4 cases of papilliform columnar
cell adenocarcinoma. The growths were described as being derived frcn

surface epithelium of the bronchi.

F. Tumors of the Alimentary Tract and Liver
Squamous cell carcinoma and lymphosarcana have accounted for the ma-

Jority of reported tuners of the alimentary tract of the cat. Reports

6
that the majority of the malignancies were of the lymphoid type, twice as
many males as females were affected, and 50% of the cats were 1 to 5 years
of age. Although nothing definite could be said about the possible etiologic
agent or agents, it was observed that many cases followed anemia, and the
possibility of overstimulation of the bone marrow was raised. 0f the 155
cases, 9 were myeloid leukemia. One of these was a basOphilic leukemia with
an enlarged spleen. The author interchanged the term basophilic leukemia
with mast cell leukemia in this report. Also mentioned were 1 case each of
eosinOphilic leukemia, monocytic leukemia, and multiple myeloma.

Squire (1964) reported that lymphosarcoma was responsible for 107. of
all feline deaths at Angell Memorial Hospital. He indicated that the condi-
tion was usually visceral lymphosarcoma. Granulocytic leukemia was rare,
and its most cannon pathologic feature was splenomegaly according to Squire.
Intraocular lymphosarcoma has been reported by Saunders and Barron (1964).
In their 2 cases, the choroid, iris, and ciliary body were involved in
both, and the retina in 1. They mentioned that neoplastic infiltration
of the cornea was often mistaken for infectious keratitis.

More rare in occurrence are reticulun cell myeloma (Holzworth and
Meier, 1957) and erythemic myelosis (Zawidzka, Jansen and Grice, 1964).

The latter group reported a case in which the bone marrow was hypercellu-
lar with a maturation arrest affecting all cell lines. Very few well
differentiated cells were present in the marrow.

Labie and Fontaine (1960) described splenic mastocytoma in 3 cats.

In each case the splenomegaly was due to infiltration by round cells with
basOphilic cytoplasm. The authors coulnented on the difficulty in dif-
ferentiating between mast cells and myelocytes of the basophilic series,
and their description closely resembled reports of granulocytic leukemia

8
dealing with these neoplasms are discussed in sections A and D. An adamanti-
name was reported by Olafson (1939), and 2 cases of salivary gland tumors in
cats were among those listed by Koestner and Buerger (1965). Tue cases of
adenocarcinoma of the intestine were described by Taylor and Rater (1954)..
In both cats the tumor took the form of a ring-like thickening in the wall
of the intestine. According to Houlton (1961) this is the usual form of
intestinal adenocarcinoma, with stenosis of the intestine and eventual
obliteration of the lumen as a frequent result.

Chang (1964) reported primary carcinoma of the bile ducts of 3 cats
whose livers were infected by flukes. The author stated that the carcinoma
was caused by the flukes, a condition that has occurred in man. This
opinion was contrary to that of Moulton (1961), who said that no etiologic

relationship was indicated in cases of bile duct carcinoma.

G. Tutors of the Urogenital System and Hasnary Gland

Pitts (1960) described a bilateral embryonal sarcoma of the kidneys of
a cat. He stated that this tumor had not been previously reported in the
cat. Carcinoma of the urinary bladder was reported by Thoonen and Hoorens
(1960).

Carcinoma of the uterus is rare in cats (Meier, 1956). Meier con-
sidered that early spaying of female cats was a factor in the low reported
incidence. Another rare tumor is the granulosa cell tumor of the ovary
(Baker, 1956). Two instances of vaginal leiomyomas that caused constipa-
tion by compressing the rectum were reported by Wolke (1963). Meier
(1957b) reported 2 cases of Sertoli-cell tumors in cats. One cat was a
bilateral cryptorchid, and it had metastatic tumors in the liver and spleen.

No feminising signs were noted in either case. Meier commented on the

9
scarcity of reported testicular tumors in the cat and considered that early
castration might be a factor in the low reported incidence.

A large number of tumors arise in the female mmnmary gland. Several
of the reports discussed in section A have indicated a high incidence of
mamary tumors in the cat (Cotchin, 1952, 1956a; Lasserre g; 51., 1938).

It is interesting that in contrast to the dog, which has a high percentage
of mixed mammary tumors, all reports concerning the cat have been of mem-
msry carcinoma or adenoma (Moulton, 1961). The mammary adenocarcinomas

apparently are not influenced by spaying (Nielsen, 1952b).

H. Tumors of the Nervous System

A glioma arising from the left half of the floor of the 4th ventricle
was described by Knowlton (1905). However, there have been few reports
of tumors of the nervous system since that time. An astroblastoma was
reported by Milka and Olafson (1936). More recently, meningiomas have
been reported by several authors (Dahme, 1957; Gonzalez-Monteagudo and
Purpura, 1959; CoOper and Howarth, 1956). Smit (1961) said that the inci»
dence of meningiomas in cats is high, but gave no specific figures.

In a series of 155 necrOpsies of cats, Luginbuhl (1961) noted 8
meningiomas. They were characterized histologically by cells arranged
in whorls and curving columns, and degenerative changes were a feature of
several of the tumors. None of the tumors in Luginbuhl's report caused
any clinical signs. Luginbuhl concluded that thorough examination of the
nervous system of cats was seldom done at necrOpsy, and therefore the
reported incidence of intracranial neoplasia was low.

Schiefer and Dahme (1962) discussed a tumor located in the right

olfactory bulb of a cat which was diagnosed as an ependymoma. Astrocy-

lO
tomes have been reported by Cooper and Howarth (1956), and Stunzi and
Perlstein (1958). Cooper and Howarth (1956) also reported the occurrence
of 1 oligodendrocytoma in a series of 60 cat brains examined histologi-

cally.

I. Miscellaneous Tumors

An extraskeletal giant cell tumor was described by Nielsen (1952a).
Carcinoma of the thyroid was reported by Holzworth, Rusted and Wind
(1955). The cat was an obese, lS-year-old castrated male. What apparently
was a true thymoma was described by Loveday (1959). The mass was located
in the mediastinum, and on histologic examination had spindle-shaped
epithelial cells arranged in whorls. These cells surrounded small eosino-

philic‘ masses which had the appearance of Hassall's corpuscles.

MATERIAIS AND METHODS

The material used in this study was taken from the registry of the
Department of Pathology, Michigan State University. All recorded instances
in which neoplastic disease had been diagnosed in cats were selected for
study. For each tumor type selected, data were recorded in tabular form
under the following headings: tumor type, sex, age range, average age,
and no data available (age and sex).

The histologic slides for each case were grouped according to the type
initially diagnosed. A11 slides had been stained with hematoxylin and
eosin (H & E) (Armed Forces Institute of Pathology, 1960). In certain in-
stances the following special stains were used to accentuate a specific
cytologic feature or to confirm the microscopic diagnoses: Heidenhain's
aniline blue (A.F.I.P., 1960), lithium silver (Curr, 1960), Mallomy's phos-
photungstic acid hematoxylin (A.F.I.P., 1960),'MayaGrunwaldoGiemsa (A.F.I.P.,
1960), and a modified reticulum technique as outlined by Lillie (1954).

All slides in the series were examined by the author and a senior
pathologist at the Department of Pathology in order to confirm the diag-
noses. The available gross descriptions for each type of tumor were recorded,
and a composite gross description was made for each type. Histologic dew
scriptions of each tumor were also recorded, and again a composite descripo
tion for each group made, emphasizing points of similarity and difference
within the group. Photomicrographs were taken of representative sections
of the majority of the tumor types, and selected gross photographs were

included for illustrative purposes.

11

RESUIIIZ‘S

I. General

Age Incidence. The age distribution is shown (Figure 1). The ages of
the subjects ranged from.under 1 to 21 years, with an average of 7.9 years.
The largest number of tumors recorded for a given group was 17, which occurred
at 6 and 11 years of age. Over 50% of the cats were under 10 years old.

The ages of 47 cats were unknown.

Sex Incidence. There were 91 males and 110 females in this series.

 

For 55 of the cases, no data were available concerning the sex of the cat.
Because records were often incomplete, no attempt was made to separate

castrated from entire animals.

Tumor Types. The basis for classifying the various neoplasms was the
cell of origin. In all instances standard nomenclature was used, with
Moulton (1961) as a guide. Using this classification, therewere 33 difa
ferent types of tumors studied (TABLE 1). These included both benign and
malignant varieties (e.g., fibroma and fibrosarcoma), as arising from 1

cell type.

Deggee of malignancy. Malignant and benign tumors are listed by
basic tissue type (TABLE 2). The column heading of "mesenchymal" includes
tumors of muscular and endothelial tissue. The column headed "questionable"
refers to tumors such as the basal cell carcinoma and adnexal carcinoma,

the behavior of which is not synchronous with the malignancy suggested by

12

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14

TABLE 1. Age and sex incidence of each tumor type.

 

 

No Data
Total _§£§L. Age Range Average Age Available
Tumor type Number M’ F in Years in Years Age Sex
Basal cell carcinoma 9 4 5 1.0-17.0 9.8 - -
Melanoma 4 2 2 9.0-17.0 12.7 - -
Adnexal carcinoma 2 - l 10.0-12.0 11.0 - l
Papilloma 2 l 1 1.0- 6.0 3.5 - -
Squamous cell
carcinoma 22 7 9 3.0-16.0 11.2 2 6
Adenocarcinoma:
All types 59 12 32 2.0-17.0 8.2 18 15
Uterus l - 1 4.0 4.0 - -
Liver 2 2 - 6.0- 8.5 7.2 - -
Pancreas 3 1 1 5.0-17.0 11.0 - l
Ceruminous gland 2 - 1 13.0- 5.0 14.0 - l
Salivary gland 1 1 - 6.5 6.5 - -
Bile duct 4 1 2 3.0- 6.0 4.5 2 1
Sweet gland 4 - 1 12.0 12.0 3 3
Mammary gland 21 - 21 4.0-15.0 10.7 4 -
Intestine 1 - 1 4.0 4.0 - -
Origin unknown 20 7 4 2.0-17.0 8.5 8 9
Adenoma:
All types 12 2 9 3.0-13.0 10.1 - 1
Mammary gland 6 - 6 5.0-15.0 9.7 - -
Pancreas 2 1 - 7.0-15.0 11.0 - l
Sweat gland l - l 8.0 8.0 - -

Sebaceous gland l 1 - 9.0 9.0 - -

15

TABLE 1--cont inued .

 

 

 

 

 

. No Date
Total _§_§_:_t__ Age Range Average Age Available
Tumor type Number M F in Years in Years Age Sex
Ceruminous gland l - 1 12.0 12.0 - -
Uterus 1 - 1 3.0 3.0 - -
Fibroma 18 7 3 5.0-10.0 4.4 9 8
Fibrosarcoma 11 3 6 2.0-21.0 8.0 2 2
Malignant ‘
Mesenchymoma l - 1 20.0 20.0 - - i4
Rhabdomyosarcom 3 2 1 4.0- 8.0 5.3 - -
Leiomyosarcoma 6 2 3 5.0-10.0 8.6 - 1
Leiomyoma 3 - 2 3.0-11.0 7.0 l 1
Mastocytoma l3 3 6 0.5-15.0 7.9 2 4
Chondrosarcoma 2 - - - - 2 2
Osteogenic sarcoma 5 3 2 8.0-15.0 11.6 - -
Osteoma 3 1 l 6.0-12.0 9.6 - 1
Osteochondrana 1 - 1 4.0 4.0 - -
Lipoma 6 2 2 2.0-11.0 7.2 2 2
Neurofibroma 2 1 l 2 . 0- 16 . 0 9 . 0 - -
Neurof ibrosarcoma 2 - l 5 . 0 5 . 0 - 1
Meningioms 1 l - 7.0 7.0 - -
Myxoma 1 1 - 13.0 13.0 - -
Myxosarcoma 1 - - - - l l
Hemangiosarcoma 3 2 - 6 . 0- 10 . 0 8 . 0 l l
Malignant lymphoma:
Reticulum cell type 14 8 3 0.7-17.0 6.7 1 3

Lymphosarcoma type 43 24 14 0.7-18.0 4.9 6 5

TABLE 1--continued .

l6

 

 

No Data
Total Sex Age Range Average Age Available
Tummr type Number M F in Years in Egars Age Sex
Mixed manmary tumor 1 - 1 12.0 12.0 - -
Teratoblastoma 1 - 1 5.0 5.0 - -
Undifferentiated
Sarcoma 4 2 2 5.0-18.0 12.3 - -
Carcinoma 3 l 1 10.0-11.0 10.3 - 1

 

 

17

TABLE 2. Tumors listed by type of tissue.

 

 

 

 

 

 

# A:E=-—
Epithelial ‘ Mesenghymal Mixed Total
Benign ll 37 1 49
Malignant 88 95 l 184
Questionable 10 13 - 23
Tot al 109 145 2 256

 

18
their names, and the cutaneous mastocytoma, which is difficult to classify

either-by clinical behavior or histologic evaluation.

II. Specific Tumor Types
All tumors are listed by type, total number, sex, age range, and
average age (TABLE 1). Also included are figures indicating no data

available regarding age and/or sex of the animal for certain tusors.

A. Epithelial Tumors ‘

Basal Cell Carcinoma. Gross: No particular site of predilection was

 

noted for this tuaor. It was usually a slowly developing lesion in the
skin and subcutis, and often was ulcerated. In several cases the clinical
diagnoses of chronic inflamation had been made.

Microscopic: Inflamatory changes were noted in the majority of the
basal cell carcinomas. The tumor cells were usually small and uniform, or
slightly pleomorphic. Nuclei were round or oval and nuclear chromatin
often was hyperchromatic. Nucleoli were usually not significantly enlarged.
The number of mitotic figures in different specimens was variable.

The tumor cells formed 2 microscOpic patterns. The most comon con-
sisted of small solid islands of cells surrounded by connective tissue
stroma (Figures 2 and 3). Isolated islands often resembled tubules. The
cells at the periphery of the island were usually arranged at right angles
to the encircling connective tissue. The other pattern was that of infil-
trating cords and loops of tumor cells. In many tumors there was a variable
amount of pigment, often in the center of the solid islands of cells. In
some tumors, the neoplastic cells made an abrupt transition from the more

normal epithelium (Figure 4).

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2. Basal cell carcinoma. Small nests of

cells separated by delicate stroma. Hematorylin and
eosin. x 188.

2’

 

Figure 3. Basal cell carcinoma. Note nests of
cells that resemble tubules, with peripheral cells
arranged perpendicularly to the basement membrane.
Hematoxylin and eosin. x 750.

 

20

‘\
. H 2
l‘ 3’.
{huh-M '

   

Figure 4. Basal cell carcinoma. Abrupt transition
from normal to neoplastic apitheliu. Some small cellu-
lar nests can be seen. Hematosylin and eosin. x 188.

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Figure'5. Squamous cell carcinoma. Note nucleoli,
tonofibrils, and dense collagenous stroma (A). Hema-
toaylin and eosin. x 188.

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21

Papilloma and Smous £911 Carcing. Gross: The 2 papillomas were
small pedunculated growths projecting from the skin. Eighteen of the 22
squamous cell carcinomas were located in the oral cavity or the skin of the
head and neck. They were usually rapidly developing tuners, and many had
recurred at least once. The majority of them was ulcerated.

Microscopic: The papillomas were canposed of a fibrous core, with
overlying epithelium that was hyperplastic and which had elongated rete
POEM ‘

Surface ulceration was a canon feature of the squamous cell carci-
nae. The tuner cells were cuboidal or polyhedral and often pleomorphic,
usually with abundant cytoplasm. Cell boundaries were usually distinct
and tonofibrils were a constant feature (Figure 5). Nuclei were large,
vesicular, and hyperchrouatic with enlarged nucleoli. Mitotic figures
were usually cannon.

The cells were arranged in cords or solid islands which infiltrated
into the dermis and subcut is, or into the lamina propria and submucosa of
the oral cavity. Dense fibrous strome was present in all tumors. Some of
the tumors had beginning "pearl" formation, but only 2 had well formed
keratin pearls .

In 1 tumor there was extreme pleomorphism and many of the cellular
elements had taken on the characteristics of mesenchymel cells. In several
cases, the center of the solid islands of tumor cells was necrotic, and

under low power magnification these areas resembled glandular acini.

Melanoma. Gross: The melanomas studied were all from the skin in
the form of small nodules less than 2 cm. in diameter. No particular

site of occurrence was noted. Pigmentation was not marked grossly.

 

 

 

 

 

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22

MicroscOpic: The ne0p1astic cells were avoid and, in many areas,
resembled young fibroblasts. Nuclei were vesicular, with moderately promi-
nent nucleoli. There were few mitotic figures. The majority of cells
carrying pigment was within or close to the overlying epithelium (Figure 6),
although some pigmented cells were scattered throughout the tumors. The
general arrangement of neoplastic cells was in curving bundles with some
whorls. Junctional changes in the epidermis were noted, but were not

prominent.

agnexal Carcinoma. Gross: This tumor occurred in the skin as a slowly
growing nodule.

Macroscopic: The tumor was made up of pleomorphic epithelial cells.
The cells had moderate amounts of cytoplasm and round to oval hyperchromatic
nuclei. MHtotic figures were not numerous. The neoplastic cells were
arranged in a solid sheet in the dermis and appeared to arise from the

epithelium of hair follicles (Figure 7).

figbsgeousgégenomg. Gross: 'The only example of this type of tumor*was
a small, slightly pigmented, hairless growth on the back.

iMicroscopic: The tumor was composed of enlarged sebaceous cells
forming enlarged but otherwise normal appearing glands (Figure 8). There
were inflammatory changes in the overlying epidermis and around some of

the glandular elements.

Sweat Gland Adenoma and Adenocarcinomg. Gross: Little information
on the gross appearance of these tumors was available, except that they

all occurred in the skin of the head region.

 

Figure 6. Melanoma. Concentration of pigment
carrying cells in the basal epithelium. Note enlarged
nucleoli of the neoplastic cells. Hematoxylin and
eosin. x 750.

0"",

 

3 4.
‘

Figure 7. Adnexal carcinoma. Small epithelial
cells clustered around the base of a hair follicle (A).
Hematoxylin and eosin. x 750.

 

 

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'- leg?

.‘ 3‘

 

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k -

Figure 8. Sebaceous adenoma. Enlarged sebaceous
cells with hyperchromatic nuclei. Hematoxylin and
eosin. x 469.

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f“i
.(.t_~

 

Figure 9. Ceruminous gland adenocarcinoma. Note
large nucleoli and prominent inflammatory reaction
(arrow). Hematoxylin and eosin. x 750.

 

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25
Microscopic: The cells were roughly cuboidal, being more pleomorphic
in the malignant tumors. The nuclei were round or ovoid with prominent
nucleoli. Mitoses were variable in number. The cells were supported by
a fibrous stroma and formed acini and ducts which were elongated, cystic,
and had papilliferous projections in the more malignant carcinomas. There
was some secretory activity in the benign tumors. Necrosis and inflammation

were constant features of these tumors.

Salivagy Gland Adenocarcinoma. Gross: The 1 example of this type of
tumor was a friable growth in the right parotid region.

Microscopic: The neoplastic cells were columnar with elongated
hyperchromatic nuclei. There were many mitotic figures. The cells were
arranged in acini which varied from round to elongate. Piling up of the
tumor cells in an asymmetrical pattern.was common, and in some areas the
glandular lumennwas almost obliterated by the cellular proliferation.

The glandular acini were separated by thin fibrous septa.

Ceruminous Gland Adenoma and Adenocarcinoma. Gross: These tumors
were located within the external ear canal. Thewaere soft in consistency,
and all had some degree of secondary inflammation. They varied from dark
red-brown to yellow-cream.

MicroscOpic: Typical tumor cells were large and cuboidal, and had
vesicular nuclei and prominent nucleoli. The malignant tumors had many
mitotic figures. In addition, the adenocarcinomas were characterized by
a moderate degree of cellular anaplasia and pleomorphism. The cells had
formed irregular acini and ducts, some with papillary infoldingS. There
was a secretion present in many acini, and extensive areas of inflammation

were common in all tumors of this group (Figure 9).

 

26

Mammagz Gland agenoma 3nd Adenocarcinoma. Gross: The only consistent

gross features were inflammation and ulceration of the tumors. Their sizes
were variable, and lymph node involvement was inconsistently noted. From 1
to several glands were involved, and recurrences after surgery were common.
Many had metastasized to distant organs.

Microscopic: ‘Mammary adenomas and adenocarcinomas assumed several
microscopic patterns. 0f infrequent occurrence was the solid type CFigure
10), where the majority of the cells was arranged in a sheet, with fibrous
strome intermixed. More common were the cystadenoma and cystadenocarcinoma.
The most common type of pattern was that of neoplastic cells arranged in
acini or glandular lobules, divided by variable amounts of fibrous connective
tissue (Figure 11).

The cells in the adenocarcinomas were similar in all patterns of
arrangement, and were somewhat pleomorphic with large hyperchromatic nuclei
and prominent nucleoli. Mitotic figures were numerous. The acini were
irregularly shaped, and of various sizes. Many had papillary projections
into the lumen (Figure 12). In some areas the proliferation and piling up
of neoplastic cells almost obliterated the acinar lumens.

Cells in metastatic lesions were more anaplastic, and acinar formation
was not as distinctive as in the primary lesion (Figure 13). Necrosis and
inflammatory exudate were commonly observed in the primary sites of mammary
tumors .

The few adenomas were only slightly altered from.the normal glandular
appearance. Mitotic figures were rare, and the acini appeared slightly

enlarged and irregular, with well differentiated glandular epithelium.

 

27

I
‘
.9

v
1

If
6

   

Figure 10. "Solid" type mammary adenocarcinoma.
Hematoxylin and eosin. x 188.

 

Figure 11. Mammary adenocarcinoma. Vesicular
nuclei with prominent nucleoli. Cells have formed
fairly well differentiated acini. Hematoxylin and
eosin. x 469. I

 

28

   

Figure 12. Mamary adenocarcinoma. Cystic acinus
with papillary projections into the lumen. Hematoxylin
and eosin. x 188.

 

Figure 13. Mamary adenocarcinoma. Metastatic
lesion in pituitary. Pleomorphic cells which have
formed acinar structures. Hematoxylin and eosin. x 188.

29

Uterine Adenoma and Adenocarcinoma. Gross: The l adenoma was reported
to be present in the "uterine tube" and was 2.5 x 2.0 cm. in size. On cut
section it appeared cystic. The adenocarcinoma was 10.0 cm. in diameter and
projected forward from the uterus toward the stomach.

MicroscOpic: The adenoma had dense collagenous stroma which contained
cystic glands of varying size. Several glands had some piling up of glandu-
lar epithelium on 1 side of the acinus.

The adenocarcinoma had neOplastic areas that varied from cystic papil-
liferous glands to more solid lobules of cells divided by thin fibrous
stroma. The cells were pleomorphic, with vesicular nuclei, prominent
nucleoli and moderate numbers of mitotic figures. There was extensive

invasion of the myometrium by neoplastic cells.

Hepgtocarcinoma. Gross: These tumors gave a diffuse nodularity to
the liver. Mbtastatic nodules were present in the spleen in both cases and
in mesenteric lymph nodes in 1 case.

'Microscopic: The neoplastic cells had nuclei that resembled the nuclei
of normal liver cells, except for some variation in size. The cells were
also hyperchromatic. The cytoplasmwwas scanty and more basophilic than
normal. Matotic figures were common.

The transitional zone from normal to neoplastic cells was abrupt, with
the adjacent normal cells compressed and displaced by the tumor masses.

The cellular pattern varied from fairly solid groups of cells to areas
divided into nests or lobules by delicate collagenous strome. The areas

between the lobules appeared to serve as vascular channels.

 

30
The metastatic lesions were composed of cells similar in appearance to
those of the primary site (Figure 14). In the metastatic lesions there was
considerable stroma and vascularity, but the lobular pattern.was not as

well developed as in the primary.

Bile Duct Carcinoma. Gross: Prhmary lesions consisted of variably-
sized nodules in the liver. The lungs consistently had metastatic lesions,
and there were often omental and peritoneal implantations.

Microscopic: Within the primary focus, a change from more normal to
neoplastic bile ducts could be seen in the portal triads. The cells were
cuboidal or columnar, with some degree of nuclear polarity evident. Nuclei
were hyperchromatic and nucleoli enlarged. Mitotic figures were variable
in number.

The primary tumors were composed of ducts which varied in appearance
from.small and fairlwaell differentiated to some that were cystic with
papillary infoldings. The liver parenchyme was destroyed and compressed
at the advancing edge of the tumor.

Cells in the metastatic lesions were usually more pleomorphic than
those in the primary, although a slight degree of nuclear polarity was
evident. In many metastatic foci, the cells formed small nests rather than

ducts or acinar structures.

Pancreatic égenoma and Adenocarcinoma., Gross: These tumors were in

the form of nodules or large masses in the pancreas. Size varied from 1.0
x 2.0 to 3.0 x 7.0 cm. The small intestine and spleen were encroached upon
and invaded by the tumor in some cases. In 1 case, there were metastases

to the lung and myocardium.

 

31

 

Figure 14. Hepatocarcinoma. Metastatic lesion in
the spleen. The neoplastic cells have large vesicular

nuclei with prominent nucleoli. Hematoxylin and eosin.
x 750.

‘0}.

_ _’ *1.‘ '., " ‘
' v“ 1. ‘EZa-r‘n‘ ' __i,’

 

Figure 15. Pancreatic adenocarcinoma. Implanted
lesion in wall of the intestine. Note the occurrence
of zymogen granules in several of the neoplastic cells
(arrow). Hematoxylin and eosin. x 750.

 

32

Microscopic: In the pancreatic adenomas, the cells were slightly en-
larged, paler than normal, and had enlarged vesicular nuclei with prominent
nucleoli. Zymogen granules were present within the cells, and the normal
glandular pattern.was only slightly altered.

The adenocarcinoma cells were pleomorphic with hyperchromatic nuclei.
The normal glandular pattern was often lost, and there was a disarray of_
cells leading to the formation of dilated irregular glandular structures.

In the metastatic lesions, some areas were fairly well differentiated,
and many of the cells contained eosinophilic material resembling zymogen
granules (Figure 15). In other areas, however, the cells were extremely

anaplastic and bore little resemblance to pancreatic glandular epithelium.

Intestiggl Adenocarcinggg. Gross: One case of intestinal adenocarci-
none was included in this study. The terminal 8 inches of the ileum had an
annular thickening, and the lumen was almost completely obstructed. The
regional lymph nodes were enlarged.

Microscopic: The cells were pleomorphic with vesicular nuclei and
enlarged nucleoli. Many mitotic figures were present. The neoplastic
process appeared to be originating at the base of an ulcerated area of
mucosa.

The cells were forming irregular and slightly cystic acini, and con-
siderable amounts of bluish-staining mucin were present and filled many
of the acini. There were neoplastic cells in acinar formation within the

submucosa and the inner layer of the muscularis (Figure 16).

Adenocarcinoma of undetermined Origin. Cross: The mmjority of these

tumors (9) occurred in various abdominal organs, lymph nodes, and mesentery.

Eight of the tumors were in the skin or mucous membranes, while 3 tumors

 

   

Figure 16. Intestinal adenocarcinoma. Neoplastic
cells in the smooth muscle. Some acini being formed
(arrow). Hematoxylin and eosin. x 469.

 

Figure 17. Mucous adenocarcinoma. Note large
neoplastic cells with foamy cytoplasm. Hematoxylin and
eosin. x 750.

 

34

were located in both the abdominal and thoracic cavities. Most of the tumors
were described as nodular masses in the various organs involved, and the range
in size was from less than 1.0 cm. to greater than 10.0 cm. in diameter.
Most of the tumors from the skin and mucous membranes had been traumatized
and were inflamed.

MUcroscopic: The adenocarcinomas in the skin and mucous membranes were
composed of cuboidal or columnar cells with rounded or oval nuclei and

enlarged nucleoli. Some had very anaplastic cells with many mitotic figures.

 

The cells were arranged in irregular acini or solid lobules divided

by thin fibrous septa. Some had papillary projections within the acini.

 

The acinar walls varied from 1 to several cells in thickness. Some of the
tumors from mucous membranes had cells that were filled with a pale bluish»
staining foamy material which was probably mmcin (Figure 17).

The general characteristics of the adenocarcinomas of the abdominal and
thoracic cavities were similar to those from the skin, but appeared more
malignant. The cells'were pleomorphic with vesicular nuclei and enlarged
nucleoli (Figure 18) andnwere very anaplastic in some cases. Matotic figu
urea were frequently seen. The acinar patterns were irregular in size and
shape. In none of the tumors in this group could the cell of origin be

determined from the material available.

Undifferentiated Carcinoma. Cross: The few tumors in this group came
from.the jaw and the forelegs.

Microscopic: The cells were large and epithelial in appearance, with
vesicular nuclei and large nucleoli. In some areas they were in sheets,
while in others the arrangement was of small nests of neoplastic cells aura

rounded by fibrous strome. No definite cell type could be determined.

 

Figure 18. Adenocarcinoma in mesentery. Very
anaplastic cells with only slight tendency toward
glandular formation. Hematoxylin and eosin. x 750.

 

Figure 19. Fibrosarcoma. Pleomorphic hyper-
chromatic nuclei, prominent nucleoli and mitoses.
Hematoxylin and eosin. x 750.

 

36

B. Mesenchml Tumors

Fibrm. Gross: Fibromas occurred randomly in the subcutaneous tissue,
the oral cavity, and the reproductive tract. They were of variable size, and
all were encapsulated. Most of them were firm and light in color. ’

Microscopic: . The cells were generally spindle shaped, with indistinct
cellular outlines. Nuclei were variable in shape, from small and rounded to
thin spindle forms. Nuclei were slightly hyperchromatic and nuclear chroma-
tin was scattered like fine dust within. Mitotic figures were rare.

The cells were arranged in wavy bundles, and little who‘rling was‘seen.
Usually the fibers were long, but occasionally they were short and gave the
appearance of a random scattering of fibers with no particular organization.

Occasionally the tumors were predominantly fibrous and acellular.

Fibrosarcgg. Gross: Fibrosarcomas were less noticeably encapsulated
and more invasive than fibromas. They tended to recur after excision and
infrequently metastasized. Many were subject to necrosis and inflamation
within the tumor.

Microscopic: The cells of the fibrosarcoma were pleomorphic, and the
cell nuclei were vesicular with enlarged nucleoli. Mitotic figures were
comon (Figure 19). The cellular pattern was similar to the fibromas, but
there was more interlacing of bundles and more tendency toward the formation

of whorls .

Malignant Mesenchmoma. Cross: The 1 example of this type of neo-
plasm was a slowly growing tumor of the gingiva..
Microscopic: This tumor was made up of fibrous tissue, smooth muscle,

myxomatous tissue, and bone (Figures 20 and 21). There were many large

 

Figure 20. Phlignant mesenchymoma. Section of "
anaplastic fibrous elements with mitotic figures (arrow).
Hematomylin and eosin. x 750.

 

Figure 21.. Malignant mesenchymoma. Myxomatous
tissue and bone. Hematoxylin and eosin. x 750.

38
multinucleated giant cells. Several of the cellular elements had malignant

characteristics.

Neurofibroma and Neurofibrosgrcoma. Gross: These tmnors were not
remarkable grossly, except that 2 of them arose in the vicinity of cranial
nerves, 1 filling the retrobulbar area and the other in the cranial cavity.

Microscopic: The cells varied from spindle and stellate to slightly
cuboidal. The cytOplasm was moderate in amount, and the nuclei of the hi
malignant tumors were hyperchromatic with enlarged nucleoli. The major

points of difference between the benign and malignant varieties were the

 

A
greater degree of anaplasia and more frequent mitoses. r
The cellular pattern was that of undulating columns and whorls, with
areas of palisading of cells. In some cases the neoplastic cells seemed

to arise from the periphery of nerve bundles (Figure 22).

Macs: and moan-coma. Cross: The myxoma was located in the subcu-
taneoustissue of the right front leg. The neoplasm was rounded, yellow,
and soft in consistency. The sarcoma was located in the liver and myocardium
of the right atrium.

Microscopic: The cells of the myxoma had a small amount of cytoplasm,
and the nuclei were rounded or ovoid to rod shaped and somewhat hyperchro-
matic. They were arranged in regular sheets in some areas and in others
were in an interlocking cord pattern of 1 or 2 cells thick. The spaces
between the cords contained an amorphous pink-blue staining material
(Figure 23). The microscopic appearance of the myxosarcoma was similar,

except for an increase in the number of mitotic figures.

39

 

\ x 1 . . ' Vt“) K

\\.\ ..
“ :m{j°‘

Figure 22. Neurofibrosarcoma. Neoplastic cells
which have apparently'originated from a nerve bundle.
Hematoxylin and eosin. x 750.

 

a, .

“ {mu

1
\

. . . _ .

- .

0m -

e t ‘

1' 9 .‘

a, "
Figure 23. Myxoma. Scattered nuclei and abundant

myxolnatous ground substance present. Hematoxylin and
eosin. x 750.

 

 

40

Msningioma. Cross: The 1 example of this tumor was a small mass located
lateral to the cerebrum.

Microscopic: The cells were spindle shaped with sparce cytoplasm.
Cell nuclei were pale and finely granular. The cells were arranged in tight
whorls and larger curving columns. Extensive degeneration and mineraliza-

tion were present within the tumor (Figure 24).

Leigoma and Leimosgrcg. Gross: The leiomyomas in this study

were from the female genital tract and appeared as nodular growths. The
largest of these was 7.0 cm. in diameter. The sarcomas arose from smooth
muscle in various areas of the body.

Microscopic: The cells of the leiomyosarcoma had slightly vesicular,
cigar-shaped nuclei, many of which appeared twisted (Figure 25). Mitoses
were not found in the leiomyomas and were infrequent in the sarcomas. The
cells were arranged in bundles that had a wavy pattern in most areas.
There was a variable amount of fibrous stroma, and in some cases it was as
plentiful as the muscle elements. One of the leiomyomas seemed to arise

from the muscular layer of small arteries and arterioles (Figure 26).

Rhgbdgzosarcoma. Gross: Gross description of these tumors was not
available. In 1 case the tumor had metastasized to the lungs.

MicroscOpic: The cells were large and bizarre in shape. Many were
multinucleated, and strap cells could be seen. The tumors had considerable
amounts of fibrous strome. Under high magnification fine striations could
be seen in some cells in sections stained with phosphotungstic acid hema-

toxylin (Figure 27).

 

 

.J

Figure 24. Meningioma. Whorling arrangement of
degenerative neoplastic cells which have undergone
mdneralization. Hematoxylin and eosin. x 750.

'
ffl7
. ‘1

 

Figure 25. Leiomyosarcoma. Although the nuclei
are pleomorphic, the "twisted" appearance of several can
be noted (arrow). Hematoxylin and eosin. x 750.

 

42

   

Figure 26. leiomyoma. The tumor cells can be seen
adjacent to the walls of the vessels (arrow). Hematoxy-

lin and eosin. x 188.

I.”

p

    
 

Figure 27. Rhabdomyosarcoma. Bizarre-shaped.

cells with faint cross striations in the cytoplasm
(arrows). Phosphotungstic acid hematoxylin. x 750.

43

M. Cross: These were variably-sized tumors which represented
circumscribed accmnulations of fat.

Microscopic: The lipomas in this series were all benign in appearance,
usually resembling normal fat. The salient feature of the microscopic

appearance was the variation in the amount of strome between the fat cells,

being nonexistent in some and moderate to dense in others (Figure 28). 1
Chondrosarcoma. Gross: No gross description was available for the 2 '11

cases in this series.

 

Microscopic: These tmnors were variable in appearance within them- '
selves. Some areas resembled relatively normal cartilage, while others
were more like a fibrosarcasa. The more anaplastic chondroblasts were
stellate shaped with vesicular nuclei and enlarged nucleoli. Often the
transitional zone between undifferentiated and differentiated elements was

abrupt (Figure 29).

Osteoma and Osteosm. Gross: One of the osteomas was a small
tumor attached to the mandible, and the other was a nodule in the subcu-
taneous tissue. Osteosarcomas in this study were variably-sized tumors
always associated with bone.

Microscopic: The osteomas were composed of mature bone, with some
evidence of a collagenous tissue capsule. Cells of the osteosarcomas were
anaplastic and pleomorphic, usually being stellate or fusiform. The cell
nuclei were hyperchromatic, and mitotic figures were cannon. Large multi-
nucleated giant cells were scattered throughout, often closely associated
with osteoid material or bony spicules (Figure 30). The osteoid material

and the bone were not uniform in occurrence. Some of the more anaplastic

K,

\

 

Figure 28. lipoma. Fat cells separated by abun-'
dant collagenous strome. Hematoxylin and eosin. x 188.

.‘ \\‘ \
K

    

Figure 29. Chondrosarcoma. Abrupt change from
anaplastic chondroblasts to more mature cartilage.
Hematoxylin and eosin. x 750.

45

 

Figure 30.‘ Osteogenic sarcoma. Stellate osteo-

blasts, osteoid, and giant cell.
x 750.

Figure 31. Hemangiosarcoma.
thelial cells around a vascular space. Hematoxylin and
eosin. x 750.

Hematoxylin and eosin.

 

Anaplastic endo-

 

46
areas in these tumors closely resembled fibrosarcomas. Hemorrhage and in-

flammation were common findings.

Osteochondroma. Gross: This tumor was located on the proximal por-
tion of the right humerus. It was cauliflower-like in shape and encapsulated.
'Microscopic: The major portion of this tumor was composed of mature
cartilage which was being replaced at 1 side by osteoid material. Some 23

mineralization had taken place. 4.1

Hemangiosarcoma. Cross: The only gross description available was

that there was intestinal involvement in 1 animal. i
Microscopic: The cells were pleomorphic, ovoid or elongated. Cell

nuclei tended to be vesicular with enlarged nucleoli. The emphatic cells

lined the vesicular channels and, in some instances, had proliferated in a

circular pattern around them (Figure 31). In less vascular areas they were

arranged in curving coltsnns or solid sheets.

Mastocztoma. Gross: Mastocytomas occurred in the skin as raised
circular plaques, often with ulceration and serous or purulent exudation.
They occurred in all parts of the body and were often diagnosed grossly as
inflamatory lesions. There were no reports of recurrences or metastases
of any of these tmnors.

MicroscOpic: The cells were variable in size and shape, being rounded,
ovoid, or sometimes stellate. (The nuclei were often hyperchromatic and
eccentrically located. The cytoplasm of the cells was usually abundant,
and granules could occasionally be seen in H 8: E-stained sections. With

Giemsa-stained sections, the nuclei were often obscured by metachromatic

47
granules (Figure 32). In the more anaplastic tumors the cells were often
difficult to distinguish from cells of the lymphoid series without special
stains.

The cells were usually arranged in sheets. The tumor cells were often
densely packed, but occasionally had a loose arrangement, with much strome
between cells (Figure 33). Occasionally they were in cords 1 cell in
thickness, which formed anastomosing patterns within the stroma. There
were eosinophils present to some degree in all the tumors. The eosinOphils
were scattered at random throughout the tunor. Inf lammatory changes were

consistently noted in the surface areas.

Malignant Lmhoma. Gross: Malignant lymphoma occurred in several
sites (TABLE 3). The gross lesions were usually nodular, of variable size,
and gray-«white or yellow (Figure 34). Occasionally there was virtual replace-
ment of an organ, such as the kidney, by neoplastic tissue (Figure 35). In
some cases both kidneys were uniformly involved. At times the masses in the
mediastinum were large enough to fill most of the thoracic cavity. When
the intestinal tract was involved, it was thickened in an annular pattern,
and the intestine was often stenotic with the lumen almost completely
obliterated (Figure 36).

Microscopic: Reticulum Cell Sarcoma type: Cells making up this tumor
were noticeably pleomorphic and had abundant cytoplasm. Some appeared
mature, and others undifferentiated and anaplastic. The nuclei were vesicuo
lar and the nucleoli were enlarged. Many of the nuclei were irregular in
shape, and often looked like myeloblastic nuclei. They were often eccen- ‘

trically located within the cells. Mitotic figures were cannon (Figure 37).

48

s“
1

*5... u‘.

 

Figure 32. Mastocytoma. Metachromatic granules
which have obscured the nucleus in many'of the neoplastic
mast cells. May-Grunwald-Giemsa. x 750.

 

,.‘

Figure 33. Mastocytoma. Note loose, scattered
arrangement of the mast cells. May-Grunwald-Giemsa.
x 188.

49

TABLE 3. Site of involvement in malignant lymphoma.

__‘ ._ 4 4.. __. __.A ! ._a. 1 fl-

 

 

__ Site ‘ _ Number of Cases
Kidney 14
Mediastinum 14
Liver 12
Sp leen 9
Internal lymph nodes 9
Lung 6
Peripheral lymph nodes 5
Gastrointestinal tract 5
Mesentery 4
Other 9

50

1.“

 

Figure 34. Malignant lymphoma, reticulum cell
type, in the myocardium.

 

 

'Figure 35. Malignant lymphoma, reticulum cell
type, which has replaced normal kidney parenchyma.

 

 

 

51

4;

 

Figure 36. Malignant lymphoma. Annular thicken-
ing of small intestine due to infiltration of lymphoid
cells. Arrow indicates lumen.

 

Figure 37. Malignant lymphoma, reticulum cell
type. Note the extreme variation in size of the cells.
Hematoxylin and eosin. x 750.

o ’5’. ¥ a

 

n-C

2.!

-
U
I
. O
' 1
~ .
'
Q
' I
I . .
I ..
C . . .
.
a“ s . . .
‘ V
. - l .
v ‘ Q‘ . . ‘
I
. U
"Q ‘
9
' O "‘ 1‘ 'S . ' :
. ..
I . ‘ I
u . .
. a
I
- ‘
0
a
Q“ s e I I ' ‘ ' 1 - '. '
.3; ~11 ..o.'.u :1 ll .0 lv .3) 7.. .g‘ 31.9 J;.. I A “0": uJ .. .0 "9.. 51“

52

The cells were in sheets, with scant to moderate strome. With a rec
ticulum stain, bundles of reticulum could be seen enclosing individual
cells or small groups of cells (Figure 38). When in organs such as the
kidney, the sheets of tumor cells had isolated and replaced the normal
architecture (Figure 39).

Lymphosarcma type: The cells of the lymphosarcoma type of malignant
lymphoma could usually be identified as lymphocytic or lymphoblastic, but
because both types or intermediate forms often occurred in the same tumor,
no attempt was made to separate them. The cells had very little cytoplasm
and round to oval nuclei which were often hyperchromatic. They were much
more regular .in appearance than the cells of reticulum cell sarcomas, and
the nucleoli, even when hyperchromic, were much smaller in size. Mitotic
figures were usually numerous, although occasionally they were few in
number.

The typical arrangement of cells was in a monotonous sheet with
variable amounts of strome (Figure 40). The cellular pattern varied from
a loose arrangement to closely packed masses of cells (Figure 41). Frau
an initial focus (or foci) in an organ, the lymphoid cells proliferated
and eventually replaced the normal architecture. In the liver the initial
cellular accumulations were in the portal areas, and in more advanced
cases the parenchyma was compressed and straphic (Figure 42). An unusual
occurrence in a few cases was involvement of skeletal muscle (Figure 43).

In this series, there was 1 case similar to the giant follicular
lymphoma of man. Within the node there was a proliferation of large
lymphoid follicles which contained pale staining lymphoblastic cells.

In addition, the node was overrun by more mature lymphoid elements and

 

Figure 38. Malignant lymphoma, reticulum cell
type. Note the reticular fibers around individual cells
and small groups of cells. The same tumor as Figure
37. Lithium Silver. 1 469.

   

{92‘s

A

Figure 39. 'Malignant lymphoma, reticulum cell
type, which has infiltrated the kidney. Hematoxylin
and eosin. x 188.

 

‘!:I.I.S.H:.’as

Figure 40. Malignant lymphoma. Mbnotonous sheets
of cells with loose arrangement. Hematoxylin and eosin.
x 750.

 

Figure 41. Malignant lymphoma. ‘Monotonous sheet
of densely packed cells. Compare with Figure 40.
Hematoxylin and eosin. x 750.

w
11‘ r «a.

%- an

 

 

 

Figure 42. 'Malignant lymphoma. Neoplastic cells
which have isolated and replaced normal liver parenchy-
ma. Hematoxylin and eosin. x 750.

X.‘ a" “i
- '1
[a ii

In?“ "

f

 
     

a

 

Figure 43. Malignant lymphoma. Neoplastic cells
in skeletal muscle. Hematoxylin and eosin. x 750.

56

in several places the capsule was invaded by the neOplastic cells.

Undifferentiated Sarcm. Gross: These tumors were all from the sub-
cutaneous areas of the body or oral cavity, except for l which was wide-
spread in many organs and whose site of origin could not be determined.

Microscopic: The cells were mesenchymal, varying from spindle-shaped
cells to smaller rounded cells. In some tumors, all gradations of cell

type existed. No definite determination of cell type could be made.
C. Mixed Cell Tumors

Mixed Mamag Tumor. Gross: This tunor was located in the inguinal
region and was reported to look like a large abscess.

Microscopic: The glandular cells were similar to those described in
the unwary adenocarcinomas and were arranged in irregular ac ini. There was
abundant collagenous tissue, and transitional areas between the collagenous
fibers and osteoid material. Glandular elements were located within the
osteoid material (Figures 44 and 45). There were also scattered small
areas of cartilagenous material and some bone. Inflammatory changes were

prominent in several areas.

Teratoblastoma. Cross: The only tumor of this type occurred as a
subcutaneous mass in the shoulder region.

Microscopic: This tumor contained epithelial elements some of which
resembled papillary adenoma and some of which were in solid islands. In

addition there were fibrous and bony elements within the tumor.

 

Figure 44. Mixed mammary tumor. Note glandular
elements within osteoid material. Hematoxylin and eosin.
3 188a

 

Figure 45. Mixed mamary tumor. Higher magnifica-
tion of Figure 44. Note glandular acini within osteoid

matrix. Hematoxylin and eosin. x 750.

DISCUSS ION

A. General

Nielsen (1964) has stated that because much is known about tumors of
the dog, and little about tumors of the cat, it is often assumed that they
are the same in histologic appearance and biological behavior, but that
such may not be the case.

The results of this study corroborate Nielsen's statement. Thirty-
three different tumors were classified by cell of origin, and noticeable
differences in their characteristics, as compared with tumors of the dog,
occurred. These points will be brought out in the discussion of indi-

vidual tumor types.

Ag; Incidencg. The average age of the cats in this studwaas 7.9
years. This is lower than the average age (9.0 years) previously re-
ported (Cotchin, 1957). One reason for this is the large increase in the
number of malignant lymphoma cases within the past 15 years and the fact
that malignant lymphoma is a disease of the younger cat. In addition,
more cats are now kept as house pets, are probably better cared for than
formerly, and receive more frequent examdnations by veterinarians.

It may be that the concept of neoplasia being primarily a disease
of the aged cat, as reports in the older literature indicated, will have

to be re-evaluated.

58

59

Sex Incidence. Without accurate normal population data it is diffi-
cult to assess these results. Schalm (1966) said that in the normal cat
population the ratio of males to females was 2:1. He does not mention the
source of his data, but if it is correct the sex incidence would be sig-
nificant, since it could mean that neoplasia is more frequent in the female

“to

B. Specific Tumor Types.
Certain tuners of cats are either more important or more interesting
from a comparative standpoint, and only those that the author considered

to be in these categories will be discussed.

hliggnt LEE . The results of this study are in agreement with
the statements of Holzworth and Nielsen (1955), and Nielsen (1964), to the
effect that malignant lymphoma is the most important neoplasm occurring in
cats. This is true not only from the standpoint of total number of tumors,
but also because of its degree of malignancy. Apparently no benign tmors
of the lymphoid tissue have been recognized in cats.

As was previously mentioned, the apparent increase in occurrence of
malignant lymphoma in the past 15 years, and the low age incidence of malig»
nant lymphoma in cats, have contributed to the lowering of the average age
of cats with tumors. Although a completely satisfactory explanation for
this is not available, several factors must be taken into account. Of
some importance is better clinical and pathologic diagnoses. More clinicians
are familiar with malignant lymphoma and are using laboratory tests which
are helpful in confirming such a diagnosis. Pathologists are also more

familiar with the condition, and many tumors which may have been diagnosed

60
as "round cell sarcomas" a number of years ago are now being placed into
the malignant lysmhoma category. In addition, many tuaors reported as
thymanes were probably malignant lymphomas involving the thymus. The
lymphoid tissues of the thoracic cavity are frequently involved in malig-
nant lmhoma in the cat, and many of these probably originate in the
thymus.

Recent reports of the apparent transmission of malignant lymphoma in
cats by cell free filtrates (Jarrett, 1964b), and the demonstration of
virus-like particles associated with malignant lymphoma in cats (Jarrett,
1964a), suggest another possible reason for the younger age of cats with
malignant lymphoma. If a virus is responsible for malignant lymphoma of
cats, it may be that early exposure is necessary, and those animals which
are susceptible would then manifest the disease after a sufficient incu-
bation period. Because of greater emphasis on preventive vaccination of
kittens for infectious diseases, more young cats are made available for
exposure to the presumed lymphoma virus, and instead of being removed from
the pepulation by infectious disease, they remain, only to become clini-
cally ill with malignant lymphoma. This theory presupposes that many cats,
for an as yet unknown reason, are either naturally innune or are able to
surmount the initial infection and are imune in later life. These
thoughts are only speculative, but such a mechanism may yet be proved.

Another interesting component of the picture of malignant lymphoma
in the cat is the predominant occurrence in the viscera, with little
peripheral lymph node involvement. Since there is often bilateral involve-
ment of the kidneys, or several sites of intestinal involvement, multi-
centric origin is suggested. Multicentric origin might in turn suggest

a carcinogen (such as a virus) which acts systemically. Why the cat has

61
predominantly visceral lymphoma as opposed to the cannon occurrence of

peripheral involvement in the dog and cow is yet to be explained.

Fibroma and Fibrosarcoma. This group of tumors comprises the 2nd
largest group in this series, a finding which sews to be at variance with
most of the reported series, as fibrous tuners seldom have occupied this
position. In addition, this is the only group having more benignpthan
malignant tumors, a condition that has been noted previously (Cotchin,
1961). No adequate explanation can be given, but histologic examination
gave the impression that few of the fibrosarcomas were very malignant.
This conclusion is further supported by the fact that they rarely metasta-

size, tending more toward local invasion.

Dis—slag g Gland Tmors. Hamary gland neoplasms of the cat are of

interest from several standpoints. Smith and Jones (1961) stated that
mamry neoplasia was cannon only in the dog. However, Nielsen (1964)
said that mannary tumors of the cat were 2nd in importance to malignant
lymphma.

The results of this study indicate that mamary neoplasms are of con-
siderable importance in the cat. They not only were 3rd in total nmnber,
but the majority of them was highly malignant.

Nielsen (1952b) said that spaying has no influence on mammary neo-
plasia of cats. This is in contrast to the condition in the dog, and more
work needs to be done to substantiate this finding and to determine the
reason for the apparent species difference.

Of special interest is the single mixed mamry tumor in this series.
It is apparent that mixed manmary tumors are rare in the cat, especially

in comparison with the fairly cannon occurrence of mixed mammary tumors in

62
dogs. As near as can be determined there are no reports of this type
tumor occurring in cats.

Although the reason or reasons for this difference between the species
are obscure, the myoepithelium of the unwary gland may play a predominant
role. Houlton (1961) suggested that it is the myoepithelial cells which
undergo metaplasia in mixed mamary tumors. Cotchin (1958a), using histo-
chemical techniques to demonstrate alkaline phosphatase, noted the enzyme
in norml canine mamary glands and in mixed mamary tumors of the dog.

A scarcity of fresh tissue from female cats has prevented the author
from studying alkaline phosphatase activity in the normal feline mamry
gland, but such a project should be undertaken. It is possible that either
a functional or anatomical difference between the feline and canine mamary
gland might explain the infrequent occurrence of mixed mamary tumors in

cats e

Squamous Cell Carcinoma. The site of occurrence of the squamous cell
carcinoma in cats is of interest. Nearly all in this series occurred in
the oral cavity or the skin of the head. This may indicate possible carcino-
genic agents or some selective mode of action of a carcinogenic agent or
agents.

Although Cotchin (1956a) and other English workers (Douglas, 1951)
have placed much emphasis on squamous cell carcinoma of the esophagus, in
this series there was no asephageal cancer of any type. These results
agree with the recent report by Brodey (1966). Cotchin considered that
the high incidence of esOphageal cancer might be due to ingested carcino-
gens, and since most of his cases were from the London area, the carcino-

genic effect of air pollution should be considered.

63

Another factor which should be considered is the licking habit of cats.
Certainly the tongue and oral mucous membranes are subject to constant low
grade trauma, and potential carcinogens could easily be taken into the oral
cavity.

As yet, however, there is no explanation for the differences in site
of occurrence of squamous cell carcinoma in England and in America. It
would seem that, unless there was a difference in carcinogenic agents, in
a random papulation the tumors would tend to occur in similar areas of the
body. This apparent geographic difference needs further study so that its
significance can be accurately assessed.

Another suggested carcinogenic agent in squamous cell carcinoma of
cats is sunlight (Moulton, 1961; Nielsen, 1964). Since the area around the
cat's ears is more lightly furred than other areas of the body, sunlight
may be of some significance, and this might explain the high incidence of

squamous cell carcinoma in the head region.

Adenocarcinoma of Unknown Origin. Many of these tunors were from the
abdominal cavity, and the question of the primary tumor site deserves con»
sideration. The possibility of overlooking a primary intestinal adeno-=
carcinoma is real, especially in a hurried or incomplete necropsy or
during exploratory surgery. The primary site of an intestinal adenocarcio
name may still be small even after metastasis has occurred, and the meta:-
static lesion, often an enlarged lymph node or mass in the mesentery, can
be more prominent than the primary. More care in performing necrOpsies

would probably eliminate the category of adenocarcinma of unknown origin.

64

iMastoczgoma. Although Cotchin (1959) and Nielsen (1964) considered
the mastocytoma to be rare in_the cat, 13 (52) of the total of this series
were mastocytomas.

The mastocytoma qualifies as something of an enigma by several criteria.
The origin and functions of the mast cell have not yet been elucidated to
the satisfaction of all, some considering it to be a "tissue basophil"
and others claiming that it has a separate histogenesis. Since there
appears to be 2 separate entities - the cutaneous mastocytoma and the rare
case of basOphilic leukemia with involvement of the viscera - the theory
of separate histogenesis seems plausible. As far as can be determined by
this series, there was no systemic involvement in the cases of cutaneous
mastocytama.

Considering the clinical behavior and histologic appearance of both
canine and feline mmstocytomas, some doubt could be cast on their status as
true neoplasms. In many of the tumors studied, the loose arrangement of
the cells resembled an inflammatory type reaction. The ever-present
eosinophils, which may be attracted by histamine, are usually considered
a component of allergic or sensitivity reactions.

The possibility of something stimulating an initial inflametory
response which, for reasons as yet undiscovered, may progress into neo-

plasia cannot be overlooked.

Basal Cell Carcinggg. Nielsen (1964) pointed out that the basal cell
carcinoma of the cat differed from.that of the dog in 2 respects. In
the cat they occurred all over the body instead of primarily the head
region, and microscopically they usually formed small islands of cells with
distinct strome surrounding them, instead of serpentine strands and cords

of cells, as in the dog.

65
The results of this series tend to confirm Nielsen's observations.
Unfortunately, no indication of the possible mechanism causing the species

difference is readily forthcoming.

general Carcinoma. Although only 2 tumors classified as adnexal carci-
noma are present in this series, they are of interest from a comparative
standpoint.

The adnexal carcinoma is a fairly frequently occurring neoplasm in
young dogs and is considered to originate from the epithelium of hair
follicles or the basal layers of the epidermis (Langham, 1966), and the
cells that make up this neOplasm resemble the cells of the histiocytoma and
the transmissible venereal tumor of dogs. When it occurs in the skin of
the dog, this neoplasm has been called the extragenital transmissible
venereal tumor. It has also been called an histiocytoma (Langhmm, 1966).

A recent report by Nowell (1965) notes that in counting the chromosomes of
the cells of the transmissible venereal tumor of dogs there were only 59
instead of the usual 78. This technique has apparently not been applied
to the cutaneous neoplasm.

The transmissible venereal tumor has not been known to occur in cats,
and this observation suggests that the adnexal carcinoma is truly a
separate entity. Many possibilities exist for fruitful research into the

adnexal carcinoma as it occurs in the cat.

Tumors of the Male Genital System. There were no tumors of this system
in the Michigan State university collection. There are apparently only 3
well documented cases in the literature. Although Heier (1957b) suggested
that early castration may be a factor, many male cats live to advanced age
without being castrated. In comparison with the dog, the relative lack of

testicular tumors in cats is an apparently valid species difference.

SUMMARY AND COMILUS IONS

This study of the neoplasms of cats was done with emphasis on sex and
age incidence, and a complete histologic description of tumor types. The
major results of this study were as follows:

1. The average age of cats in this series was 7.9 years, which is
younger than the average age of cats with tumors in previous reports.

2. Slightly more males than females were affected, but significant
conclusicms could not be drawn without normal population data.

3. The majority (72%) of the neoplasms of the cat was malignant.

4. The most common neoplasms in terms of total numbers were the
malignant lymphoma, tumors of fibrous tissue, mammary tumors, and the
squamous cell carcinoma.

5. A single mixed mammary tumor was noted, although no reports of
this neoplasm occurring in cats were noted in the literature.

6. Although most of the neOplasms of the cat were similar in histoo
logic appearance to those of other species, there was a difference in the
histologic characteristics of the basal cell carcinomas of the cat.

Several conclusions were drawn from this study:

1. ‘More such studies are necessary in order to obtain a clearer
picture of the natural occurrence and characteristics of neoplasms of
cats, and to indicate which tumors are most important and deserve more

research.

66

 

67

2. More accurate records must be kept, in order to have more valid
data. Practicing veterinarians should be encouraged to furnish canplete
histories with all surgical and necropsy specimens they submit.

3. Malignant lymphoma and mary gland tumors were considered the
most significant neoplasms of cats in this series.

4. While neoplasms of the cat have much in comon with neoplasms of
other species, there are also many unique aspects of their biological

behavior and occurrence which warrant further investigation.

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VITA

The author was born in Los Angeles, California, January 25, 1939.
He received his primary and secondary education in southern California,
graduating from high school in 1956. He entered the University of Cali-
fornia at Davis in 1956 and received his 8.5. in Veterinary Science in
1960 and his D.V.M; in 1962. While enrolled at the university he was a
member of the A.V.M.A. Student Chapter and Phi Zeta.

Following graduation from veterinary school the author entered the
U. S. Air Force veterinary Corps. He spent 3 years with the veterinary
service at the U.S.A.F. Hospital Tachikawa, Japan, and was then assigned
to Michigan State University under the Air Force Institute of Technology,
Civilian Institutions‘Training Program.

The author holds the rank of Capt. USAF V.C., and is soon to enter
the residency program of the Veterinary Pathology Division, Armed Forces

Institute of Pathology.

73

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