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and Giemsa solutions for comparison with the myelocytes found in the blood
stream. The myelocytes comprising the tumor were found to be identical with
those in the blood stream and were at a nearly com.parable stage of development.


Many myelocytes contained round polychromatophilic granules and some spindle-
shaped acidophilic granules (Plate V, Figure 2). Mathews (17) stated that bone
marrow taken from any part of the skeleton in his series of cases of myelocytoma
showed some neoplastic-like hyperplasia. The bone marrow of the femur was
examined in 15 of the cases in this study (in 5 cases no marrow was preserved),
and in all there were areas considered to be identical with the extrameduUary foci
of neoplasia. In many of the cases examined, the granuloblastic e'ements of the
marrow were almost entirely converted to a tissue resembling myelocytoma.

An infiltration of the mucosa of the intestine, especially in the duodenum, was
apparent upon gross examination of two cases. These consisted of small gray
masses representing villi swollen with an infiltration of myelocytes. In three
other cases, infiltration of the intestinal mucosa was found upon histological

Data on egg production were available on only three cases of m\'eloc\toma
(Table 12). Two of the birds could be considered good producers of eggs and the
third was a poor producer. The average production index was 0.610, or slightly
higher than that found in cases of lymphocytoma. Egg production ceased, on an
average, 21 da\s preceding necropsy of the three cases.

Table 12. — Data on Egg Production of Chickens with Myelocytoma.

Productive life is the interval between first and last eggs laid.
Production index is the factor obtained by dividing the number of eggs laid
by the productive life in days.

Age at Productive Number of Production Interval from

Case No. Necropsy Life Eggs Laid Index Last Egg to

(Days) (Days) Necropsy


T31 *K 319 133

T 2426 D 389 105

T681 D 308 90

Average 339 109 67 .610 21










*K indicates that bird was killed for examination; D, that it died.

Fowl Leukosis

The collection of neoplasms of the chicken contains 19 cases of fowl leukosis
(Plate X, Figures 5 and 6). Both erythroblastic (17 cases) and granuloblastic
(2 cases) forms of the disease were found. Since the general pathology of spon-
taneous fowl leukosis is well discussed elsewhere, no attempt is made to describe
the general pathological findings. The pathology was similar to that of cases
previously described (Feldman and Olson 8).

The average age at necropsy of chickens with leukosis was appro.ximateh' 47
weeks, or slightly older than in cases of lymphocytoma (Table 13). The sex
distribution was 17 females and 2 males, or a ratio of 8.5 to 1. The average
percentage of bod\' weight for the liver, spleen, and kidne\- in 12 cases of leukosis
is indicated in Table 13. This value is lower than in cases of hmphocxtoma for
the li\"er and kidne\', and slightly higher for the spleen.


Table 13. — Summary of Data on Nineteen Cases of Fowl Leukosis.
Figures in parentheses indicate number in group.

.\ge at Necropsy Weight of Organs Expressed

(Weeks) as Percent of Body Weight

Died Killed Liver Spleen Kidney

(10) (9) (12) (12) (8)

Maximum 114 99 9.12 1.87 1.18

Minimum 16 24 3.75 .39 .54

Average 47.7 47.5 6.71 .99 .76

A fibrosarcoma of the musculature in the region of the scapula was found in
one case of erythroblastic leukosis. The tumor measured appro.Kimately 3X
3.5 X 2 cm. and was infiltrative in character. It represents an interesting finding
because of the potentiality of some strains of the leukosis agent to induce fibro-
sarcoma (21). Lymphocytoma of the kidney and proventriculus was associated
with one case of erythroblastic leukosis. In one case of leukosis, a slight en-
largement of the posterior portion of the nerve of Remak was noted, which proved
to be due to an infiltration of erythroblastic cells. This may have been caused by
escape of leukotic cells from the blood and their local proliferation in the tissue.
Hermorrhage had occurred in six cases. In four of these, capillar}- hemorrhage
was found in either the intestinal mucosa or subcutaneous tissue; and in the
other two, hemorrhage came from rupture of the liver and spleen capsule re-

Both cases of granuloblastic leukosis were associated with myelocytoma. In
one, foci of myelocytoma were found in the liver, kidneys, ovary, bone marrow,
thymus, pancreas, and under the parietal peritoneum of the sternum. In the
other, the myelocytoma was not so widespread, involving only the liver, kidneys,
ovary, and bone marrow. The diagnosis of leukosis in both of these cases may be
open to question. The pathology of the marrow may be regarded as the most
significant feature in support of the diagnosis of leukosis. Both erythropoiesis
and granulopoiesis were stimulated far beyond normal limits and the foci of
myelocytoma found upon histological examination were confined to localized

Encroachment of the marrow by infiltration of any tumor tissue will affect the
normal function of bone marrow but this does not lead to leukosis as indicated
by the findings in cases of hmphocytoma or other cases of myelocytoma, where
replacement of myeloid tissue may cause an aplastic anemia or leukopenia. In
some instances immature blood cells may enter the circulation because of a mech-
anical disturbance b\- the tumor in the marrow.


The diagnosis of fibroma was made on five tumors in the collection. In these
cases the type cell of the tumor was a neoplastic fibroblast more mature in char-
acter than that observed in fibrosarcoma. A brief description of the five cases

1. T 40. A 4-week-old male chicken was found dead with a growth in the
subcutis immediately below the left eye. The tumor mass measured 4 X 2 X 1.5
cm. and weighed 13 grams. There was no evidence of metastasis and the cause
of death was not determined.


2. T 25 L Swelling of the right eye and excessive lacrimation was noted
in a 32-week-old hen. The bird was killed for examination. A tumor mass in
the right nasal passage and sinus was found to be responsible for the swelling
of the eye. The tumor was irregular in outline, firm, and contained several
small cysts. The cysts were lined with columnar epithelium and probably rep-
resented portions of the respiratory mucosa pinched off by growth of the fibroma.

3. T 253. A 28-week-old pullet was noted as slightly dull and submitted
to the laboratory for examination. Upon necropsy, a large tumor weighing 190
grams was found in the wall of the large intestine about 2.5 cm. from the vent.
The tumor encircled the intestine, though the lumen was eccentric in position
(Plate \T, Figure 1). The substance of the tumor was very tough and fibrous
(Plate VI, Figure 3).

4. T 293. A male, killed for examination at the age of 15 weeks, was found
to have a slight swelling of the region over the right nasal sinus. A tumor meas-
uring 20 X 12 X 10 mm. was found in the nasal sinus displacing the structures
lateral to it.

5. T 1327. A one-year-old pullet died from cannibalism. In the left ventricu-
lar wall of the heart was a firm, gray mass measuring approximately 3X2X1
cm., which proved upon section to be a fibroma (Plate VI, Figure 2). A Van
Gieson's preparation was made of a section of the tumor to eliminate the possi-
bility of the tumor's being of muscular origin. The reaction was characteristic
of fibrous tissue. A record of the egg production of this bird was available.
It had laid only 32 eggs during a productive life of 98 days, which gives a produc-
tion index of 0.326. This is lower than the average for the flock. (See section
on Lymphocytoma for discussion of the production index.) The last egg was
laid 80 days previous to the death of the bird.

It is of interest to note that in two of the five cases, the fibromas were located
in the nasal sinus. In one case of fibrosarcoma, also, the tumor was in the nasal
sinus. These facts suggest that the nasal sinus is a likely site for the develop-
ment of fibroblastic tumors, although a survey of the literature on avian tumors
does not bear out the suggestion.

Although fibromas are ordinarily considered benign, the tumor was the primary
reason for examination in four of the cases and represented the principal path-
ological finding.


Two cases of m}"xoma were found in the collection. A short description of
each follows.

1. T 81. A 6-month-old Rhode Island Red male was found dead. Its ab-
domen was filled with a 717-gram tumor attached to the left kidney. The surface
of the tumor was smooth, glistening, and yellow-white in color. On cross section
the tissue of the tumor was spongy and cystic and much distinctly mucinous
fliuid could be pressed from the cut surface. Most of the left kidney was de-
stroyed by the tumor. The tumor was composed of a ver}- loose arrangement
of small stellate cells with anastomosing processes. No metastatic or implanta-
tion nodules of tumor could be found.

2. T 197. A 7-week-old Barred Plymouth Rock male was submitted for
examination because of swelling in the region of the left eye. The bird was killed
and examined. A yellow-white, irregularly lobulated tumor was found in the
orbital cavity, which caused protrusion of the left eye. The histology of the tumor
was similar to that of case T 81. No other pathology was found.

The morphology and mucin production of the type cell of these two tumors
clearly indicates their embryonal character (Plate VI, Figures 4 and 5). Although
myxosarcomas (malignant tumors of the same t\pe cell) ha^e been found in
the chicken by different observers (Olson 20), no additional cases were found in
the present sur\ey.




Tumors found in 16 chickens were diagnosed as fibrosarcoma. These cases
art listed in Table 14 together with pertinent data.

Table 14. — Dat.a. on Sixteen Cases of Fibrosarcoma.

Case Age

No. (\\'eeks"l


Primary Site

Extension or Metastasis

T 18

*K 36


Muscle of left leg


T 60

K 52


Muscle of left leg

Gizzard and duodenum


D 60


Muscle of left leg


T 112

K 26


Muscle, near scapula



K 69


Muscle, right pectoral


T 44

D 79


Muscle, cervical region


T 134





T 62

K 12


Peritoneum, pelvic cavity



D 52




T 191



Lungs, bilateral



D 51




T 102

K 20




T 818

K 54

Male •



T 271

K 28


Subcutis of leg


T 214

K 16


Pharyngeal region


T 99



Nasal sinus

Peritoneum, muscle of leg

*K indicates that bird was killed for examination; D, that it died.

Fibrosarcoma was found most often (six cases) as a primary tumor of skeletal
muscle. In two cases metastasis to the visceral organs had occurred, and in
another case there was metastasis to the brain.

The peritoneum was considered the primary site of the tumor in three cases.
In two of these the tumors were multiple, small nodular masses scattered over
the serosal surface of the mesentery and some of the visceral organs. In one
of these cases the entire intestinal tract and mesentery were drawn into a tight,
compact mass by a dififuse covering of the peritoneum with fibrosarcoma. In
case T 62, a 530-gram encapsulated tumor found in the pelvic cavity, where it
displaced the cloaca and rectum to the right, was considered to have originated
from peritoneum although its precise point of origin could not be determined.

Bilateral fibrosarcomas were found in the lungs of one chicken and in no other
site. These may represent multicentric points of origin or a spread from one lung
to the other.

In the remaining six cases of fibrosarcoma the primary site of the tumor was
the kidney, the liver, the subcutis of the leg, the region of the pharnyx, and the
nasal sinus.

Although there was some A'ariation in the histology of the different cases of
fibrosarcoma, the type cell of the tumors was a neoplastic spindle-shaped fibro-
blast (Plate VII, Figure 1).

The majority of birds with fibrosarcoma were killed for examination, but there
were onl\- two in which the tumor could be regarded as an incidental finding.
In other words, the tumor was usually responsible for the disturbance in health
that led to necropsy. The age of birds affected with fibrosarcoma ranged from


12 to 79 weeks with an average of 42,0. Thirteen of the birds were females and
three were males.

Data on egg production were available for only one bird, case T 44. This bird
laid 168 eggs during a production period of 328 days. The production index of
0.512 was only slightly lower than the average (0.534) for the flock from which
the bird came. The last egg was laid only 41 da\'s before the bird died.


Only one example ot osteochondrosarcoma was found. This developed on the
skull, dorsal and posterior to the external canthus of the left e\e.

1. Case T 234. The owner had noted a swelling on the head of the hen and
submitted it for examination at the age of 5 months. The tumor did not seem to
discommode the bird. The mass measured approximatel)' 3X 2.5 X 2 cm. It
was firmly attached to the bone of the skull and on cross section many small yellow
bony foci were found scattered throughout the substance of the tumor. The
major portion of the tumor was faintly blue-gray in color and had a glassy ap-
pearance. Microscopically the tumor was composed principally of immature
chondroblasts which had produced much intercellular chondromucin. There were
scattered areas in which the chondroblasts assumed a more adult form resembling
cartilage cells, and in these areas were deposits of calcareous material indicating
the formation of bone (Plate VII, Figure 3). The liver, spleen, and bone marrow
of the femur were found to be negative for pathology upon both gross and his-
tological exmaination.


Only one case of fibrochondrosarcoma was encountered.

1. Case S 2630. This tumor was found in the subcutis of the back, in the
pectoral muscle, in muscles of the thigh, and in the tendinous, aponeurotic at-
tachments of muscles to the sacrum and patella of a year-and-a-half-old hen
that was killed for examination. The visceral organs and the bone marrow were
essentially negative for pathology. The cellular morphology of the tumor was
somewhat variable in different areas. In genera! it was a mixture of immature
fibrcblast-like cells and immature, neoplastic cartilaginous cells. The latter type
of cell was usually predominant. The cartilaginous cells were more or less closely
related in a syncitial arrangement. The nuclei were sometimes double and in
differentiated areas quite similar to those of adult cartilage cells. The cytoplasm
of the cells was a slate-blue color with hematoxylin and eosin stain and as men-
tioned above the cell borders were sometimes indistinct. The fibroblast-like
cells were spindle-shaped with faintly blue staining cytoplasm and had relatively
large vesicular nuclei. Transitional forms between the two types of cells were

The primary site or point of origin of the tumor could not be determined. The
tumor of the subcutis manifested itself as areas of thickening of the skin, one of
the largest of which measured 35 mm. in diameter. The tumor tissue was gray
in color, very firm and fibrous. In the muscles, the tumor had a similar color
and appearance and tended to infiltrate and destro>' the muscle tissue.

From the data on egg production by this bird a production index of 0.463 was
calculated (93 eggs in 201 days of productive life). The last egg was laid 247
days previous to necrops}-.

Histiocytic Sarcoma

The term histiocytic sarcoma has been introduced by Jackson (13) to include
those tumors which take their origin from the histiocyte. The diagnosis of
histiocytic sarcoma lequires careful microscopic study of the complex structure of
such tumors. Neoplastic histiocytes may assume the form of macrophages,
fixed stellate cells, and fibroblasts, in addition to intermediary forms between
these cell types. Usually all forms of neoplastic histiocytes may be found to a
variable extent in different parts of a typical histiocytic sarcoma.


Three examples of this tumor were found. A brief description of each of these
cases follows:

1. T 5. A 7-month-old pullet was killed for examination because of symptoms
of general debility. A tumor mass weighing 217 grams was found in the region
of the pancreas. Histological section revealed that although it did not actually
invade the pancreas this organ was markedly compressed by encircling growth
of the tumor. In some areas the tumor was distincth' fibroblastic in character.
In other areas the tumor was composed of large, round cells possessing a relatively '
large vesicular nucleus with a large, distinct nucleolus. In still other areas the
arrangement was much less compact and the cells were stellate with anastomosing
cell processes. Areas of necrosis were found in the tumor with a polyblastic
reaction composed of lymphocytes, plasma cells, and granulocytes on the serous
surface of the tumor mass. A marked lymphoc\tic h\'perplasia was observed
in the liver, kidney, and proventriculus. Hyperplasia of the myeloid elements
of the bone marrow was present in which the development of granulocytes was
largely definitive.

2. T 52. A somewhat emaciated hen, one year old, was killed by the owner
and submitted for examination. There was an e.xcess of cloudy, \'ellow peritoneal
fluid containing masses of rather dry, yellow debris. The visceral serosa was
distincth- thickened and the mesentery was shortened causing the intestinal
tract to be contracted into a small, firm mass from which it was impossible to
separate individual loops of intestine. The liver was enlarged and contained
numerous, variable-sized foci of white tissue the largest of which measured 1 cm.
in diameter. The centers of these foci were depressed giving them a crateri-
form appearance. Many of the masses were confluent and others had a sharp,
discrete border. The ovary appeared normal and non-functioning yet on section
a rather large mass of tumor was found replacing the parench\'ma. The tumor
covering the serosa and in the liver and ovary was variable in its histological
aspect and resembled that found in the case previously described.

3. T 280. This case was a 7-month-oId pullet which was killed for examina-
tion. A moderate swelling was noted over the left pectoral region. The swelling
was found due to a tumor mass in the subcutis overlying the left breast muscle
and extending the length of the sternum. The tumor tissue was gray-\ellow in
color and enclosed cavities some of which were filled with dark brown fluid, while
others contained brown or red, gelatinous, fibrinous material. The tumor was
intimately associated with the underlying muscle. Both lungs were quite firm
and almost completely infiltrated with gray-\ ellow tissue. The tumor in the region
of the breast was composed of a mixture of fibroblastic and large macrophage-like
cells (Folate VII, Figure 2). Debris of engulfed cells was evident in the cytoplasm
of the large macrophages. In some areas the cytoplasm of the fibroblast-like
cells had become fused to form a relatively solid mass of tissue. The histologx'
of the tumor in the lungs was similar to that in the breast region. An incidental
finding in this case was a small benign hemangioma occurring as a small nodule
in the liver.

Jutlging from experience with these cases, considerable study is required to
make a differential diagnosis between histiocytic sarcoma and fibrosarcoma;
yet essential difterences occur which indicate that these tumors ma>' be regarded
as separate and distinct forms of neoplasia.

Neurogenic Sarcoma

Five neoplasms aniong the collection of chicken tumors were classified as

neurogenic sarcoma. One of these (Case 447) has been previously described

(Olson 23) and the others are new to the literature. The salient features of the
five cases are as follows.

1. Case 447. A pullet was killed for examination at the age of 23 weeks after
having shown symptoms resembling those of fowl parahsis for about a month.
A firm, encapsulated mass was found attached to the elements of the right brachial
nerve plexus. Some of the tumor was growing in the vertebral canal and com-
pressed the spinal cord. The greater mass of the tumor extended toward the base
of the heart and the thyroid gland, being connected with the part in the vertebral


canal by a slender stalk. Histologically the tumor was composed of spindle-
shaped neoplastic fibroblasts. The visceral organs and other parts of the nervous
system were normal.

2. T 312. A 14-week-old female chick, weak and pale from coccidiosis,
was killed for examination. No symptons of paralysis were noted. At the apex
of the left lung was a smooth, white nodukir mass about which the adjacent
lung tissue was molded. Upon dissection the nodule was found to arise from the
first thoracic dorsal root gangUon on the left side (Plate I, Figure 1). The tumor
extended outward from its origin and infiltrated the adjacent musculature to some
extent. It had to be separated from the periosteum of the first rib by cutting.
The lung was not infliltrated by the tumor. The entire mass was irregular and
measured approximately 3X 2.5 X 2 cm. The first thoracic nerve and the small
branch from the ganglion to the brachial nerve plexus were not involved. The
tumor consisted of fairly well differentiated fibroblastic cells which were ar-
ranged in bands and had a tendency to assume whorl-like arrangements. The
brain and other portions of the nervous system were examined histologically
and found to be normal.

3. T 97. A 29-week-old pullet was killed for examination. The bird was in
poor flesh and somewhat inactive. An irregular mass of firm, white, glistening
tumor tissue was found in the subcutis of the coccygeal region to the left of the
mid line. The mass measured appro.ximately 4.5 X 3.5 X 2.5 cm. The tumor
infiltrated the adjacent soft tissue to a slight extent. A stalk of tumor, 2.5 mm.
in diameter, passed through an opening in the underlying bone and connected
with a large mass of similar tissue spread irregularly in the left sublumbar and
subsacral region. The tumor enveloped two posterior dorsal root ganglia of the
left lumbosacral nerve plexus. The left psoas muscles were infiltrated b)' the
tumor which also partially encircled the left kidney without invasion. A portion
of the tumor extended between the left kidney and vertebral column and formed
a large mass medial and caudal to the posterior pole of the left kidney. The
histological appearance of the tumor was somewhat variable in different locations.
In some areas there was a dense, compact arrangement of plump, spindle-shaped
cells with oval nuclei. In other areas the cells were less numerous and arranged
in strands with anastomosing processes. In the less dense areas there was con-
siderable amorphous intercellular material and clear, fissurelike spaces. The
cells also tended to form whorl-like structures in the less dense portions. A sec-
tion cut through one of the dorsal root ganglia of the sacral region showed the
complete replacement of the fibrous capsule by tumor. Focal accumulations
of lymphocytes were found in the dorsal root ganglia of the brachial plexuses
and in one of the ganglia of the lumbosacral plexus. These lesions were similar
to those seen in fowl paralysis. The peripheral nerves and the nerve ganglia of
the anterior mesenteric plexus were normal. The visceral organs were essen-
tially negative for pathology.

4. T 288. A 24-week-old pullet was found dead. Previous to death it had
been lame on the left leg. The dorsal root ganglia and radicals to the left lumbo-
sacral plexus were embedded in an irregular mass of dense fibrous tumor tissue
(Plate I, Figure 3). The tumor was intimately associated with the periosteum

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