Mantle Cell Lymphoma with Histological Progression to Pleomorphic Lymphoma in Two Cattle

An abattoir survey for bovine enzootic leukosis revealed that severe splenomegaly and hepatomegaly were observed in a heifer (case 1) and a steer (case 2), respectively, in addition to great enlargement of certain lymph nodes. Both cases tested positive for bovine leukemia virus (BLV) by polymerase chain reaction. Histologically, the neoplastic tissues in case 1 were characterized by a mantle zone growth pattern of medium-sized cells showing a transition to highly pleomorphic and atypical cells. Similar histological characteristics were also observed in case 2, but neoplastic mantle cells forming focal lesions were more pleomorphic than in case 1. B cell markers CD20 and CD79a were expressed in cases 1 and 2, as well as CD5 and cyclin D1, which are important markers for human mantle cell lymphoma. Cases of pleomorphic B cell lymphoma with large abdominal tumor masses are thought to be derived from body cavity B-1 cells, whereas this study suggests that nodal pleomorphic B cell lymphoma is of mantle cell origin.