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 



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 



