An unusual pleomorphic sarcoma in a hybrid mallard

An unusual pleomorphic sarcoma from a hybrid mallard (Anas platyrhynchos) is described. Rhabdomyosarcoma was considered in the original differential diagnoses but rejected due to lack of specific characteristics generally seen in these tumors. The histologic characteristics described are consistent with mammalian sarcomas recorded in the literature as malignant fibrous histiocytoma.