36 MASS. EXPERIMENT STATION BULLETIN 391 



when persistent might reasonably lead to hypertrophy of the muscles. Jackson 

 (13) has called attention to the predisposition of smooth muscle in the ovary and 

 oviduct for proliferation. Sometimes this hypertrophy appears to progress 

 beyond functional requirements, thus leading to the development of a benign 

 neoplasm. Other factors must also be involved, for all hens with prolonged, 

 heavy egg production do not necessarily develop a leiomyoma of the mesosalpinx 

 and there was no direct correlation between the size of the tumor and production 

 index in this series. 



Two birds with leiomyoma also had carcinoma of the ovary, and four others 

 with smooth muscle tumors had mixed tumors (carcinosarcoma) of the ovary. 

 The latter four cases are discussed in more detail in the section dealing with 

 carcinosarcoma. 



Rhabdomyoma 



Tumors derived from voluntar\- muscle tissue are usually considered rare, 

 and indeed but few cases in the chicken hav^ been described. Eber and Malke 

 (4) mentioned finding multiple rhabdomyoma in a poorly developed breast muscle 

 of a hen, and Reitsma (28) described a case in which multiple tumors were found 

 in the muscles of the maxilla, thorax, and abdomen. Peyron and Blier (26) 

 described a malignant myoma the size of an apple found in the leg of a rooster. 



Two cases of neoplasia were diagnosed as rhabdomyoma in this study. 



L T 303. An 8-month-old male, lame on the right leg, was killed by the 

 owner and submitted for examination. Isolated multiple tumors were found en- 

 closed within the sheaths of several muscles. These were found in the flexor 

 and extensor muscles in both thighs, in both pectoral muscles, and in muscles on 

 both sides of the thorax at the level of the second and third ribs. The largest 

 tumor measured 25 mm. in diameter and 35 mm. in length and was found in an 

 extensor muscle of the left thigh. The tumors were spindle-shaped, conform- 

 ing in general to the shape of the affected muscle. A striking feature was the 

 bilateral symmetry of location of 'the individual tumor masses. The visceral 

 organs and peripheral nerves were normal. The tumors were of a similar histologi- 

 cal composition. Malignant spindle-shaped cells replaced the muscle tissue 

 although bundles of degenerating muscle fibers were scattered in some areas. 

 The tumor cells were relatively long with tapering ends when viewed in longi- 

 tudinal section, and a very fine fibrillary character of the c\toplasm was noted. 

 On cross section, the cells were round and, when cut through the nucleus, the 

 latter occupied approximate!},- one-fourth the space of the cell. Longitudinal or 

 cross striations were not noted in sections stained with the routine hemato.xylin 

 and eosin combination. The nuclei of the tumor cells were elongate and some- 

 what vesicular. Mitotic figures were infrequently noted. The cells lay in rows 

 parallel to each other but did not tend to arrange themselves in compact bundles 

 although in some instances the cell processes seemed to anastomose with adjacent 

 cells. A fibroblastic stroma with well-developed collagen fibers formed a sup- 

 porting framework for the tumor. A Van Gieson's preparation of sections of the 

 tumor indicated the myogenic character of the tumor cells, as the cjtoplasm 

 had the staining property of muscle tissue. 



2. T 141. The bird providing material for this case was a 10-month-old 

 pullet which had given a suspicious reaction to a test for puUorum disease and 

 was killed for examination. An irregular tumor mass measuring 20 X 15 X 7 

 mm. was found in the posterior edge of the semitendinosus muscle at about the 

 middle of the thigh. The tumor was white and relatively firm. Another small 

 tumor nodule was found on the wall of the small intestine opposite its mesenteric 

 attachment. In cross sections of the muscle tumor the connective tissue forming 

 the sheaths of the secondary and tertiary bundles was increased in amount and 

 restricted lateral growth of the tumor. At the edges of the affected secondary 

 and tertiary bundles were degenerated muscle fibers, the majority of which had 

 been replaced by the tumor. The tumor tissue itself was variable in different 

 areas (Plate XII, Figure 4). In some areas the cells were rather plump and 

 widely separated by amorphous intercellular material. In other areas the cells 

 were more compact. In general the cells were elongate and had a fine character- 



