Epidemiological, clinical and pathological aspects of follicular lymphoma in dogs

Follicular lymphomas are a rare form of lymphoproliferative disorder described in veterinary medicine. Together with the probable non-existence of Hodgkin's lymphomas in dogs, this is the biggest difference about lymphoma between humans and dogs. The aim of this article is to describe the epidemiological, clinical and anatomopathological findings observed in five dogs with follicular lymphoma. Of the five dogs with follicular lymphoma, two were male (40%) and three were female (60%). The age of affected dogs ranged from 11 to 13 years. Four of the five (80%) dogs were purebred and one (20%) had no defined breed. All dogs presented generalized lymphadenomegaly and splenomegaly, which included cases as multicentric lymphoma. At necropsy, the lymph nodes and the spleen demonstrated a nodular pattern at the cut surface, characterized by tens to hundreds of white nodules of variable size, multifocal or coalescing. On the natural surface of the spleen, often (4/5, 80%), there were myriads of white, multifocal or coalescing dots of varying sizes. In histopathology, the tumors were confirmed as follicular lymphomas. All cases were Grade Ill, two (40%) included as Illa and three (60%) as IIIb. In one case (1/5, 20%), follicular lymphoma was considered as a IIIb variant of small centroblasts similar to the neoplastic lymphocytes seen in Burkitt's lymphoma. Lymphomas were validated as having origin in B cells through immunohistochemistry, using anti-CD20 antibody. The cases of follicular lymphomas described behaved aggressively and led the patients to death.