LYMPHOPLASMACYTIC LYMPHOMA IN A STALLION

Lymphoplasmacytic lymphoma found in a 6-year-old Anglo-Arabian stallio n was investigated histologically, immunohistochemically and ultrastru cturally. The animal showed a large mediastinal mass and generalized l ymph node involvement. The neoplastic cells were in various differenti ation stages of small lymphocyte, centrocyte, centroblast, immunoblast and plasma cell. Some neoplastic cells showed positive cytoplasmic re activity for mu and lambda chains. There were well developed rough end oplasmic reticulum (RER) and Golgi complexes in plasmacytoid cells, an d slightly developed RER or a few long strands of RER in medium-sized to large lymphoid cells. These findings suggest that this neoplasm is of B-cell origin.