Lymphoid neoplasms in swine.

Seventeen cases of lymphoid neoplasms in swine were investigated and divided into eight histological types. Cases 1-3 were precursor B lymphoblastic leukemias, which occurred in three piglets from the same dam. Cases 4 and 5 were diagnosed, respectively, as a precursor B lymphoblastic lymphoma and a thymic B cell lymphoma, because there were cytological differences between the lymphomas. These five cases of immature B cell malignancies expressed CD79a and terminal deoxynucleotidyl transferase (TdT). Mature B cell lymphomas were divisible into follicular (case 6), diffuse centroblastic (case 7) and intestinal large B cell (cases 8-11) lymphomas. Unlike in case 7, the neoplastic cells in cases 8-11 showed cytological features intermediate between centroblasts and immunoblasts. The mature lymphomas were characterized by positive immunolabeling for CD79a and cytoplasmic immunoglobulins. A case of thymic γδ T cell lymphoma (case 12) were positive for CD3, CD5, WC1 and TdT. Instead of TdT, perforin was expressed in γδ T cell lymphomas (cases 13-17), whose histological characteristics were epitheliotropism, homing into T cell zones of lymphatic tissues, and cytological atypia and pleomorphism. In the present study, lymphoid neoplasms could be classified into discrete histological types, some of which were considered to be specific for swine.