Rosette-forming multicentric B-cell lymphoma in a giant panda.

Literature covering diseases of the giant panda (Ailuropoda melanoleuca) is either in Chinese or focuses on infectious agents. Here we describe the clinical signs, gross and microscopic findings, and immunohistochemistry results of a B-cell lymphoma in multiple organs of a 35-y-old captive male giant panda. The animal was euthanized because of prolonged anorexia and vomiting. Postmortem examination revealed ascites, generalized lymphadenopathy, splenomegaly, hepatomegaly, and thickened gall bladder mucosa. Histologically, the architecture of these organs was effaced by a densely cellular neoplasm composed of large, CD79a-positive neoplastic B lymphocytes supported by a fine fibrovascular stroma. Neoplastic cells occasionally palisaded around an eosinophilic fibrillary center, sometimes resembling Homer Wright rosettes. To our knowledge, rosette-forming lymphoma has not been reported previously in animals.