52 MASS. EXPERIMENT STATION BULLETIN 391 



tumors. The number of cases of neoplastic disease which passed unobserved in 

 the present survey cannot be estimated, j'et some may have occurred. Careful 

 consideration was given to all material at the time of necropsy before it was re- 

 jected as non-neoplastic. Many suspicious cases which later proved to be other 

 than neoplastic in character were included for histological study. Differentiation 

 between neoplastic and non-neoplastic conditions from macroscopic examination 

 is usually considered fairly simple. It will be noted, however, that some errors 

 were made in such differentiation in the present survey. Bacteriological and other 

 examinations to determine the etiology of lesions will sometimes assist in dif- 

 ferentiating between neoplastic and non-neoplastic conditions. However, 

 since neoplasia and granuloma may exist simultaneously in the same bird, the 

 diagnosis of a granulomatous process does not necessarily eliminate the exis- 

 tence of neoplasia in a given chicken. 



The degree of accuracy of tentative diagnoses as shown in Table 26 represents 

 two correlations calculated from the data. One correlation indicates the per- 

 centage accuracy of recognition of cases actually found to be the respective types 

 of neoplasia. For example, 108 of 153 lymphocytomas were recognized on 

 macroscopic examination as lymphocytoma (71 percent). The other correlation 

 indicates percentage accuracy of all tentative diagnoses. For example, 127 

 tentative diagnoses of lymphocytoma were made and 108 cases proved to be 

 lymphocytoma (85 percent). Correct tentative diagnoses were made in 182 of 

 301 instances of neoplastic and non-neoplastic diseases thus indicating a degree 

 of accuracy of 60.4 percent. The degree of accuracy varied considerabl}-. To 

 illustrate, leiomyoma and embryonal nephroma were usually correctly recog- 

 nized, whereas epithelioblastoma and fibrosarcoma were not. 



A rather high degree of accuracy was obtained in the tentative diagnosis of 

 lymphocytoma, since 108 of the 153 cases of lymphocytoma were correctly 

 identified. The -45 which were not correctly identified were confused with a 

 wide variety of conditions (Table 26). The differentiation between lymphocytoma 

 and myelocytoma on macroscopic features alone should not as a rule be difficult 

 (Plates II and IV). In an occasional lymphocytoma with an extremely diffuse 

 character, relatively soft texture, and unusually white color, the absence of 

 periosteal involvement should be of assistance in differentiation. When this 

 characteristic of periosteal involvement is not present in cases of myelocytoma, 

 differentiation may be difficult. Although only eight of the fifteen myelocytomas 

 (53 percent) were recognized at the time of necropsy and eight of the seventeen 

 tentative diagnoses of myelocytoma proved correct (47 percent), this type of 

 tumor usually has distinguishing characteristics and should be more readily 

 identified on gross examination. Eleven of the sixteen cases of leukosis were 

 identified (69 percent) and the same proportion of tentative diagnoses of leukosis 

 proved to be correct. Leukosis may at times be difficult to differentiate from 

 lymphocytoma if blood smears are not examined. The three cases of leukosis 

 which were called lymphocytoma were quite similar. A brief description indicates 

 the lack of differential features in these cases. In each the moderately enlarged 

 liver was reddish-brown in color with a diffuse gray stippling, the bone marrow 

 grayish red, the spleen slightly or moderately enlarged, and the kidne>s uniformly 

 swollen. Such a description might obtain for either disease and the correct differen- 

 tial diagnosis of such cases may be extremely difficult without the aid of histologi- 

 cal examination. Leukosis was confused also with granulomatous and inflammatory 

 liver changes in a limited number of cases. Texture and consistency are important 

 factors in the differentiation between lymphocytoma, epithelioblastoma, and 

 fibrosarcoma, particularly in cases involving the abdominal organs such as the 

 peritoneum, pancreas, and ovary. Epithelioblastoma and fibroblastoma are 

 usually very firm and may be particularly difficult to differentiate from each 



