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gross examination only. This phase of the work should be of importance to those
doing diagnostic work who have neither the time nor the facilities for histological
study o'f material submitted to them for diagnosis.

Chickens suspected of neoplasia at the time of necropsy were carefully ex-
amined and sections of organs involved or suspected of involvement were pre-
pared for histological examination. Smears of the blood were prepared when
possible from chickens suspected of a blood dyscrasia. The routine procedure
for histological e.xamination was to use a hemotoxylin and eosin stain of formalin-
fixed material. Special methods were used in some instances when required to
establish a diagnosis.

A stud\' of neoplastic diseases must necessarily have a scheme for naming
and classifying the various forms of tumor encountered. In this connection
much use was made of the standard books dealing with oncology. The works
of Ewing (5), Feldman (7), and Jackson (13), particularly, have been of invaluable
assistance in this respect and they, together with the contributions of other in-
vestigators mentioned in the text of this article, have served as guides for the
stud\' of the tumors encountered in chickens. The scheme of classification
adopted is presented in Table 1. In general it follows the commonly used, simple
scheme of classifying tumors according to the tissue from which they are derived.
In the schematic classification are listed only those varieties of neoplasia which



^The authors are indebted to Dr. W. A. Hagan, New York State Veterinary College, Ithaca,
N. Y., tor permission to use certain material collected while one of them (CO.) was associated
with that institution.



4 MASS. EXPERIMENT STATION BULLETIN 391

were found in the group of cases studied. Other varieties found in the chicken
by others could be readily fitted into the general scheme as outlined.

Table 1. — Schematic Classification of Neoplasms Found in Chickens,

L Tumors of hemoblastic origin.

A. Lymphocytoma

B. Myelocytoma

C. Leukosis

II. Tumors of connective tissue

A. Benign

1. Fibroma

2. Myxoma

B. Malignant

1. Fibrosarcoma

2. Fibrochondrosarcoma

3. Osteochondrosarcoma

4. Histiocytic sarcoma

C. Special forms of connective tissue tumors

1. Neurogenic sarcoma

in. Tumors of epithelial tissue (Epithelioblastoma)

A. Benign

1 . Papilloma

2. Adenoma

a. Hepatoma

b. Cholangioma

B. Malignant

1. Adenocarcinoma

2. Carcinoma

C. Special forms of epithelial tumors

L Th>'moma

IV. Tumors forming blood and lymph spaces

A. Hemangioma

B. Lymphangioma

V. Tumors of muscle tissue (Myoblastoma)

A. Leiomyoma

B. Rhabdomyoma

VI. Tumors of serous membranes

A. Mesothelioma

VII. Tumors of pigmented tissue

A. Melanoma

VIII. Mixed Tumors

A. Embryonal nephroma

B. Carcinosarcoma

C. Teratoma

Despite the apparent simplicity of such a classification certain difficulties arise.
For example, thymoma has been placed under the general heading of "Tumors of
epithelial tissue" and might with equal justification be placed in the group of
connective tissue tumors or in the group of mixed tumors. In general the termi-
nology is that commonly accepted for the various types of neoplasia, although



NEOPLASTIC DISEASES IN CHICKENS 5

some exceptions will be apparent upon examination of the list. The terms
"neurogenic sarcoma" and "carcinosarcoma" are specific examples and their
use is discussed in the sections dealing with those tumors.

Some discrepancy may be noted in the relative space allotted for the descrip-
tion and discussion of the different types of neoplasms. Justification for this
apparent overemphasis of certain t\pes of less common tumors may be sought
in the fact that the study has added relatively more to our fund of information
concerning these particular types.

DESCRIPTION OF SPECIFIC FORMS OF NEOPLASIA OBSERVED

Lymphocytoma

Comments and Classification

More than half (213) of the cases in the collection fell into the classification
of lymphocytoma. Such a high frequency for this type of tumor in chickens is
not surprising. Despite the fact that lymphocytoma is such a common form of
neoplasia, however, there has been no satisfactory method or criterion offered
for separating the different manifestations of the disease. Some cases are asso-
ciated with lesions of the nervous system; some cases have a diffuse distribution
of the neoplastic lymphoid cells; and in other cases the foci of neoplasia are
nodular.

For the purpose of study, the cases of hmphocytoma were separated into
groups with particular emphasis on the characteristic behavior of the neoplastic
tissue as observed from both gross and microscopic examination. Minute cyto-
logical details such as the size of the lymphoid cells, the ratio betw^een size of
nucleus and size of cell, and the relative num.ber of mitotic figures were not consid-
ered in the subdivision of the lymphocytomas although these features were taken
into account at the time the individual cases were designated as lymphocytoma.
The degree of involvement of the various organs or tissues was classified in four
grades at the time of histological examination. In Grade 1 the tumor was con-
fined to a few areas; in Grade 2, there were several areas of neoplasia; in Grade 3,
a moderate amount of parenchyma was replaced by tumor cells; and in Grade 4,
the majority of parenchyma of an organ or tissue was overgrown or displaced by
the tumor. Classification of degree of involvement of such tissues as the mus-
culature, skin and subcutis, and peritoneum was based on the local invasiveness
at the site of the tumor. Such a procedure is not necessarily recommended for
routine classification of lymphocytomas.

A preliminary survey indicated that the lymphocytomas could be separated
on the basis of their morphological characters into six groups according to the
following scheme:

Those with nerve tissue involved
L Diffuse lymphocytoma

2. Nodular lymphocytoma

3. Combined diffuse and nodular lymphocytoma

Those with no nerve tissue involved

4. Diffuse lymphocytoma

5. Nodular lymphocytoma

6. Combined diffuse and nodular lymphocytoma

Diffuse Lymphocytoma. — The common characteristic of the group classified
as diffuse hmphocvtoma was a diffuse infiltration of the involved organ or tis-
sues with neoplastic lymphoid cells (Plate II, Figures 1, 2, 3; Plate III, Figure 1).
The majority of the lymphocytomas (118 cases) were of this type. In 51 cases



6 MASS. EXPERIMENT STATION BULLETIN 391

nerves, as well as other tissues, were infiltrated with lymphoid cells (Plate III, Fig-
ure 2 and Table 2). The gross appearance of organs affected with diffuse lym-
phocytoma varied with the extent of infiltration. When the organs were severely
affected, they were enlarged and the normal color was interspersed with the
gray-white of tumor tissue. In some instances the organ was almost completely
replaced by tumor and the color was then gray-white. Occasionally the foci of
tumor were localized and had irregular indiscrete margins. Some organs showed
infiltrations upon histological examination when there was no evidence of tumor
from the gross examination (Plate II, Figure 1).

Table 2. — Classification qf 213 Cases of Lymphocytoma.

Form of Tumor



No Nerves
Involved


Nerves
Involved


Total


67


51


118


38


2


20


45


30


75



Diffuse

Nodular

Diffuse and "Nodular

Total 130 83 213



Nodular Lymphocytoma.- — The group of nodular lymphocytomas comprises
those cases in which the neoplastic lymphoid tissue was in the form of nodules
more or less encapsulated by a wall of connective tissue (Plate II, Figures 2, 4,
5; Plate III, Figures 3, 4). Only 20 cases of nodular lymphocytoma were found;
in 2, the process also involved nerve tissue. The nodular character of the tumor
was usually apparent from gross observation, although in some instances what was
suspected to be a diffuse lymphocytoma was found to be nodular upon histological
examination (Plate 11, Figure 2). Generally the nodular arrangement was more
pronounced in the liver and spleen than in other sites.

Diffuse and Nodular Lymphocytoma. — Cases of hmphocytoma in which the
neoplastic tissue had characteristics of both diffuse and nodular forms were
fairly common (75 instances among the series of 213 lymphoc>tomas). In some
cases the organs were affected with both forms of neoplastic infiltration, and
in other cases one form of tumor was found in some organs and the other form
was found in other organs. The gross appearance of organs and tissues of the
cases included in this group was a combination of the appearance of organs
affected with diffuse lymphocytoma or nodular lymphocytoma (Plate II, Figure
2. Although actualh' nodular l\mphoc\'toma, the process in the liver resembles
the combined diffuse and nodular form).

Characteristic Features

The six groups of cases were studied by comparison with each other to find an
explanation for the different manifestations characteristic of each group. Al-
though the data do not provide clear-cut results, some things are suggested which
lead to interesting speculation.

Age at Necropsy. — The youngest chicken found to be affected with hm-
phocytoma was a 6-week-old female which was killed for examination and found
to have a Grade 4 diffuse lymphocytoma of the ovary and a Grade 1 nodular tumor
of the spleen. The oldest bird found to be affected was a 104-week-old female
that had a diffuse lymphocytoma infiltrating the lumbar and ischiadic nerves
and adjacent musculature on one side. The average age of the 114 birds killed



NEOPLASTIC DISEASES IN CHICKENS 7

for examination was 32.8 weeks, and most of these were moribund. Birds
with lymphocytoma involving nerves were significantly younger when killed
(Table 3). This is no doubt due to the fact that birds with nerve involvement
showed symptoms (caused by the nerve lesions) earlier than birds with no nerve
involvement, and the chickens were submitted for examination because of the
symptoms. There was no significant difference between the six groups in age
of birds that died (Table 3).

Table 3. — Age of Birds at Necropsy in 213 Cases of Lymphocytoma.

Age is expressed in weeks with standard error of the mean. Figures in parentheses
are number of cases in group.





of Tumor


Died — Age in


Weeks


Killed — Age


in Weeks


Form


No Nerves
Involved


Nerves
Involved


No Nerves
Involved


Nerves
Involved


Diffuse.




.. 36.7+2.6


36.2 + 7.6


39.4+3.4


29.4 + 2.0


Nodular




(44)
.. 36.6 + 5.1


(12)
32


(23)
41.5+3.8


(39)
23


Diffuse and Nodular. . . .


( 8)
.. 35.8 + 4.2
(23)


( 1)
31.2 + 5.1

(11)


(10)
33.9+3 6

(22)


( 1)

26.8 + 2.7

(19)



Sex. — The effect which the factor of sex ma\- have on lymphoc\'toma is some-
what difficult to determine from the data. There were 193 females and 20 males
represented in the 213 cases, which is a ratio of 9.7 to 1. A similar ratio of 9.7
to 1 existed in the 118 cases of diffuse lymphocytoma; but the ratio dropped to
4 to 1 in the 20 cases of nodular lymphoc\toma and increased to 14 to 1 in the
75 cases of combined diffuse and nodular lymphocytoma. There was a slight
and perhaps insignificant difference in the sex ratios of the cases of lymphocytoma
with nerve infiltration and those without involvement of nerves. The ratios
were 12.8 to 1 (83 cases) and 8.3 to 1 (130 cases), respectively. These results
suggest that a male is more apt to have the nodular form of the disease than a
female and that a female is more apt to have the diffuse and nodular form of the
disease than a male. The incidence of lymphocytoma in male and female chickens
is covered miore fulh under incidence in sexes in the general discussion.

Seasonal Occurrence. — More cases of lymphocytoma were encountered during
the first and last quarters of the year than during the second and third quarters
(Table 4). Such frequency of incidence during these periods must be correlated
with the ages of the birds aS the majority of chickens in commercial poultry
plants would be about 35 weeks old during the first and fourth quarters of a
year. This subject is covered in more detail in the discussion on incidence of
neoplasia. An interesting feature was the shift of high incidence of lympho-
cytoma in which nerves were involved from the fourth to the third quarter. This
fact must also be correlated with the observation that such cases occurred in
birds slightly younger than those in which no nerves are affected. When all 83
cases of lymphoc\toma with involvement of nerves are considered, there were
two peaks of high incidence, these being in the first and third quarters of the year.
This finding has not been explained. The various types of lymphocytoma (diffuse,
nodular, and diffuse and nodular) were essentially similar with respect to their
incidence in the different quarters of the year.



8 MASS. EXPERIMENT STATION BULLETIN 39 L

Table 4. — Lymphocytoma: Correlation of Quarter of Year at Necropsy

AND Type of Disease.

Figures represent percent of cases occurring in the respective quarters of the year.
Figures in parentheses are number of cases in the group.



No Nerves Involved Nerves Involved Total



Form of

Tumor 1*



Diffuse and










Nodular.


35.5


8.9


6.7


48.9




(16)


(4)


(3)


(22)



Diffuse.... 23.9 22.4 25.4 28.3 33 3 11.7 27.5 27.5 28.0 17.8 26 2 28.0

(16) (15) (17) (19) (17) (6) (14) (14) (33) ,21) (.31) (33)

Nodular... 33.3 22.2 16.6 27.9 — — 50.0 SO.O 30.0 20.0 20.0 30.0

(6) (4) (3) (5) — — (1) (1) (6) (4) (4) (6)

30.0 16.6 36.8 16.6 33 3 12.0 18 7 36.0

(9) (5) (11) (5) (25) (9) (14) i27)

Total... 29.2 17.7 17.7 35.4 31.4 13.2 31.4 24.0 30.0 16.0 23.0 31.0

(38) (23) (23) (46) (26) (11) (26) (20) (64) (34) (49) (66)

*1 indicates first quarter of year including months of January, February, and March;
2 indicates the following three months: and so on for 3 and 4.



Distribution of Lesions. — In the group of cases studied, lymph&c\ toma was
found to affect nearly every organ or tissue in the chicken. The order in fre-
quenc\- of involvement was as follows: liver, gonad, kidne\', spleen, nerve, peri-
toneum, adrenal, intestine, marrow, lung, pancreas, heart, bursa of Fabricius,
proventriculus, skeletal musculature, skin and subcutis, thymus, thyroid,
parathyroid, and oviduct (Table 5).

The arrangement of lymphocytomas into groups according to type led to
interesting results in connection with the distribution of lesions. The tumor,
when nodular in form, was found to be confined to fewer organs and to affect
certain organs more frequently than others. In the 20 cases of nodular lympho-
cytoma, the liver was involved in 18 (90 percent) and the spleen in 17 (85 per-
cent). The kidney, gonad, lung, thymus, adrenal, intestine, and proventriculus
were more frequently affected in cases of combined diffuse and nodular lympho-
cytoma than in the other forms of the disease. The marrow, peritoneum, skin
and subcutis, musculature, heart, pancreas, and bursa of Fabricius were involved
about as often in the diffuse type of lymphocytoma as in the combined diffuse
and nodular lorm. (Chart 1.)

Certain differences in the frequency of organ involvement were apparent
between those cases in whi.^h nerves were also affected and those in which nerves
were not affected. The liver, spleen, kidney, marrow, and bursa of Fabricius
were more frequently affected in those cases of lymphocytoma with no nerve
infiltration. The lung, peritoneum, skin and subcutis, musculature, adrenal,
heart, and proventriculus were more commonly affected when nerves were in-
filtrated. In some instances (liver, spleen, and adrenal) the difference was marked.
Essentially similar differences were noted when the respective types of lympho-
cytoma with and without nerve involvement were compared as when the entire
group of cases was separated on the basis of infiltration of nerves only and com-
pared as is done in Tables 5 and 6.

The nerve tissue most commonly involved with Ismphocytoma was that in.
the region of the anterior mesenteric plexus. Other sites frequently infiltrated
with the tumor are listed in Table 5.



NEOPLASTIC DISEASES IN CHICKENS



PER CENT



too 60 60 ¥0



20

I



20

i__



^O

_j



60 SO fOO




LIVER
SPLEEN
KIDNEY
GONAD
PERITONEUM
ADRENAL
INTESTINE
MARROW
LUNG
PANCREAS
HEART .
BURSA OF fABR/CIUS
PROVENTRICULUS
SKIN AND SUBCUTIS
MUSCULATURE
THYMUS
THrPOIb
PARATHYPOIO
OVfDUCT
BLOOD



All * COMB/NCD FODM (7^)
NOOULAR (20)



N£ fives NOT tNVOLVCD (fjo)
AJ£H\/£S IN VOL VED f6^)



Chart 1. The Relative Frequeno' of Organ Involvement in 213 Cases of Lymphocytoma.
The cases are listed twice: on the right-hand side, on the basis of nerve involvement; and on
the left-hand side, on the basis of form of disease. The number of cases in each classifica-
tion is indicated in parenthesis in the kev.



10



MASS. EXPERIMENT STATION BULLETIN 391



Table 5. — Frequency of Organ Involvement with Lymphocytoma.

Figures represent percent of cases in which the respective organs or tissues were
involved. Cases are grouped twice: according to form of tumor and on the basis
of nerve involvement. Figures in parentheses are number of cases in group.



Form of Tumor



Organs or

Tissues

Involved



Diffuse



(118)



Diffuse
Nodular and
Nodular
(20) (75)



Nerve Involvement

No

Nerves Nerves

Involved Involved
(130) (83)



Total
(213)



Liver 37.3

Spleen 22.9

Kidney 47 . 5

Gonad 53 . 4

Marrow 11.9

Lung 17.8

Peritoneum 32 . 2

Skin and Subcutis 9.3

Musculature 10.2

Thymus 4.2

Adrenal 28.0

Heart 11.9

Pancreas 11.0

Intestine 17.8

Bursa of Fabricius 6.7

Proventriculus 5.9

Thyroid 3.4

Parathyroid 1.7

Oviduct 2.5

Blood 22.9

Nerves —

Anterior mesenteric. ... —

Brachial —

Lumbar —

Ischiadic —

Vagus —

of Remak —



90
85.0
40.0
30.0
30.0
5.0
15.0



5.0
20.0



10.0



72.0

65 5

58.7

57.4

29.3

25.3

30.7

8.0

8.0

8.0

37.4

12.0

17.3

26.7

16.0

20.0

6 7

2.7

21.4



70.7

56.1

55.4

50.8

25.4

15.4

23.8

4.6

4.6

6.1

19.2

9.2

10.7

19.2

15.4

7.7

2.3



24.6



30.1

24.1

43.4

55.5

10.8

25.3

33.8

13.3

14.5

3.6

44.6

14.5

14.5

20.5

4.8

14.5

7.2

4.8

2.4

15.7

60.2
56.6
51.8
27.8
27.8
24.1



54.5

43.6

50.7

52.5

19.7

19.3

30.0

8.0

8.4

5.2

29.1

11.3

12.2

19.7

11.3

10.3

4.7

1.9

1.4

21.1

23.4
22.0
20.2
10.8
10.8
9.4



The disease was found to involve more organs or tissues when diffuse or nodular
and diffuse in character. Nodular lymphocytoma was usually confined to few
organs (Table 6).- Lymphocytoma was confined to only four or less organs
(exclusive of the various nerves and blood) in 61.9 percent of the 213 cases studied.
The extent of lymphocytoma was about the same irrespective of whether or not
nerves were involved, when the nerve tissue itself was left out of consideration.

The different combinations of organs or tissues that might be affected with
lymphocytoma were studied. In this study involved nerves and blood were
excluded. Actually 152 such combinations were found. As mentioned above,
the liver, spleen, kidney, and gonad were the organs most frequently affected
with lymphocytoma, and there were only 28 of the 213 cases in which none of
these four organs was involved. Of these 28 cases, 25 were dift'use lymphocytoma
(representing 21.2 percent of the group of 118 cases of dift'use lymphocytoma)



NEOPLASTIC DISEASES IN CHICKENS



11



and the other 3 were of the combined diffuse and nodular form (4 percent of the
group of 75 cases of combined diffuse and nodular lymphocytoma). In 31 cases
of lymphocytoma, one organ only was involved with tumor. Lymphocytoma was
confined to the ovary in 10 cases, the peritoneum in 5 cases, the liver in 3, mus-
culature in 3, the spleen in 2, the kidney in 2, the lung in 2, the bursa of Fabricius
in 2, the skin and subcutis in 1, and the adrenal in 1. Single-organ involvement
with lymphocytoma was distributed among the forms of disease as follows:
diffuse, 24 cases; nodular, 4 cases; and diffuse and nodular, 3 cases. In 14 cases,
lymphocytoma was distributed in one of two combinations: liver, spleen, kidney,
gonad, and marrow (7 cases) ; and liver, spleen, and kidney (7 cases). The next most
frequent combination was liver and spleen only (5 cases).

Table 6. — Number of Org.ans or Tissues Involved with Lymphocytoma.

Figures represent percent of cases with the respective number of organs or
tissues involved. Cases are grouped twice: according to form of tumor and on the
basis of nerve involvement. Figures in parentheses are number of cases in group.







Form of Tumor


Nerve Involvement




Number of

Organs or

Tissues

Involved*












Diffuse

ai8)


Nodular Diffuse and
Nodular

(20) (75)


No Nerves

Involved

(130)


Nerves
Involved

(83)


Total
(213)


1


20.3


20.0 4.0


13.1


16.9


14.5


2


17.0


15.0 17.3


13.8


21.7


16.9


3


18.6


20.0 8.0


16.1


13.3


15.0


4


17.0


20.0 12.0


16.2


14.5


15.5


5


14.4


15.0 21.4


20.8


10.8


16.9


6


7.6


5.0 9.3


7.7


8.4


8.0


7


2.5


5.0 14.7


6.9


7.2


7.1


8


1.7


— 5.3


2.3


3.6


2.8


9


.9


— 4.0


2.3


1.2


1.9


10





— 2.7





2.4


.9


11

12

13


a


— —














— 1.3


.8





.5



♦Organs or tissues considered are those listed in Table 5, with the exception of the various nerves
and the blood.



Degree of Involvement. — In over half of the cases where either the gonad,
skin and subcutis, musculature, or bursa of Fabricius was affected with lympho-
cytoma, the degree of involvement of these structures was Grade 4 (Table 7).
Organs less severely infiltrated were the liver, spleen, kidney, lung, peritoneum,
pancreas, and intestine, although in over half of the cases in which they were
affected the degree of involvement of these tissues was classified as either Grade
3 or Grade 4. The marrow, thymus, and proventriculus were not often severely
involved, as more than half of the cases in which they were affected were of either
Grade 1 or Grade 2. The 64 cases in which the adrenal was involved were dis-
tributed almost equally in each of the four grades. Nerve tissue when affected
usually had a Grade 3 involvement. The blood was considered to be affected
when cells similar to those of the tumor were found in the blood of the vessels.
This condition was different from the leukemic state found in fowl leukosis.
The blood when involved usuallv fell into the classification of Grade 1 or 2.



12



MASS. EXPERIMENT STATION BULLETIN 391



Table 7. — Degree of Involvement of Organs and Tissues in 213 Cases of

Lymphocytoma.

Figures express percent of affected organs or tissues having the respective
degree of involvement. Figures in parentheses are the number of cases in which
the organs or tissues were affected with lymphocytoma.



Organs or Tissues
Involved



Number

of
Cases



Grade 1



Degree of Involvement*'



Grade 2



Grade 3



Grade 4-



Liver

Spleen

Kidney

Gonad

Marrow

Lung

Peritoneum

Skin and Subcutis. . . .

Musculature

Thymus

Adrenal

Heart

Pancreas

Intestine

Bursa of Fabricius. . . .

Proventriculus

Blood

Nerves

Anterior mesenteric.

Brachial

Lumbar

Ischiadic

Vagus

of Remak



116)
93)
108)
112)
(42)
41)
64)
17)
18)
11)
62)
24)
26)
42)
24)
22)
45)

50)
47)
43)
23)
23)
20)



9
23

21
5
35
15
13

17
27
24
17
8
14

14
44

24
21
12

4
5



16
21
26
11

24
22
23
6
II
27
24
17
12
19

41
40

16

11
16
13
17
20



27
28
35
16
17
39
22
29
17
19
28
53
38
28
13
31
16

30
30

47

44

•48

45



48
28
18
68
24
24
42
65
55
27
24
13
42
39
87
14



30
38
25
43
31
30



*Graded from 1 to 4, with Grade 1 representing a small amount of tumor and Grade 4 heavjr
infiltration.



Estimation of the degree of inv^olvement of the blood was difficult to make
and subject to considerable error. The recognition of a neoplastic lymphoid
cell in the blood stream represents a problem in itself. Most of the observations
on the condition of the blood were made by noting the blood contained in the
vascular bed of the sections of tissue at the time of histological examination.



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