HYPERGAMMAGLOBULINEMIA AND MYELOMA IN FIVE TIGERS (): CLINICOPATHOLOGICAL FINDINGS.

Five adult tigers ( presented with a range of clinical signs, including paresis (2/5), lameness (2/5), ataxia (3/5), anorexia (5/5), and lethargy (5/5). Each tiger demonstrated elevated plasma globulin levels (7.8-14.8 g/dl; [reference interval 2-5.1 g/dl]) on routine biochemistry, confirmed as a monoclonal gammopathy using protein electrophoresis. Serum gammaglobulin concentration ranged from 5 to 7.5 g/dl, or 45.1-63.4% of total protein concentration. Azotemia was present in three tigers. Diagnostics and management varied with the presenting signs but included magnetic resonance imaging, radiography, chemotherapy, supportive care, and euthanasia. In each case, necropsy revealed a neoplastic plasma cell proliferation in the bone marrow and one or more extramedullary sites. Lytic lesions in the thoraco-lumbar spine were found in three animals, and one lesion was associated with spinal cord compression. Splenomegaly was present in 4/5 cases. Histopathology confirmed a plasma cell neoplasm in each case, and immunohistochemistry staining with multiple myeloma oncogene 1 (MUM1) was positive in each case. CD20 staining was performed in two cases and was positive in one. CD3 staining was performed in the same two cases, and was negative in each. Based on the clinical, gross, microscopic, and immunohistochemical findings, myeloma was diagnosed in all five tigers.