Chronic T-cell Lymphocytic Leukemia in a Black Swan ( Cygnus atratus ): Diagnosis, Treatment, and Pathology.

Abstract An asymptomatic 14-year old, male black swan (Cygnus atratus) housed at a zoological institution was presented for routine preshipment examination. Hematologic findings indicated that the bird had a severe lymphocytic leukocytosis, consistent with chronic lymphocytic leukemia. Radiographs showed the presence of multiple soft tissue masses within the caudal coelomic cavity; ultrasound showed one mass to be an enlarged spleen, a cystic mass near the gonads, and a mass suspected to be associated with the ventriculus. Results of further antemortem diagnostics, including bone marrow aspiration, fine-needle aspirate cytology of the coelomic masses, and immunohistochemical staining confirmed T-cell leukemia with infiltration of the bone marrow and the spleen. The bird showed partial response to treatment with chlorambucil, lomustine, prednisone, l-asparaginase, and whole-body radiation, with neither evidence of adverse effects nor clinical signs of disease. Although the leukemia showed response, there w...