Pathological and immunohistochemical studies of follicular lymphoma in two calves.

Pathological and immunohistochemical studies were performed on two cases of bovine follicular lymphoma with severe leukaemia and antibodies to bovine leukaemia virus. Histologically, numerous neoplastic follicular structures were observed in the lymph nodes and spleen of both cases and in the tonsils and Peyer's patches of one case. The neoplastic cells infiltrated diffusely into the liver, lungs and heart in both cases and into the tonsils, kidneys, abomasum and bone marrow in one case. Intracytoplasmic immunoglobulin was negative in the neoplastic cells. Follicular dendritic reticulum cells were decreased in number in the neoplastic follicles compared with those in normal lymphoid follicles. Follicular lymphoma is rare in cattle. Histological features of the present cases are distinguishable from the adult form of bovine lymphoma and the calf form of lymphoma.