Histopathological definition of the adult and calf types of bovine leukosis.

Histopathological distinctions were examined on 36 cattle 2 months to 12 years of age affected with leukosis. The distribution of tumors pointed out previously as the characteristic of the adult type of leukosis was observed in 27 adult cases, which, except two, were positive for the immunodiffusion test of bovine leukemia virus (BLV). The noticeable development of massive and lumpy tumors in serosa, loose connective tissue, and lymph nodes seemed to suggest a neoplastic accumulation in areas related to the lymphatic way. Splenic involvement and intrasinusoidal leukotic immigration in the liver were present in cases with the leukemic manifestation of peripheral blood. The neoplastic involvement of bone marrow, however, was difficult to find. On the other hand, in 5 calves and 4 adolescent or adult cattle, the neoplastic proliferation was observed throughout such hematopoietic organs as lymph nodes, bone marrow, liver, spleen, thymus and tonsil. The hepatic lesion was characterized by the neoplastic proliferation in the portal triads No BLV antibody could be detected from these cattle, except one adult. As the conclusion of the present study, the tumor of adult type regarded as the pathologic manifestation of enzootic bovine leukosis is defined as malignant lymphoma (non-Hodgkin's lymphoma or lymphosarcoma) of undifferentiated-, histiocytic-, or poorly- differentiated lymphocytic- cell type. And lymphocytic leukemia seems to be desirable term to distinguish the lymphoid malignancy regarded as the characteristic of the calf type from that of the adult type.