Endocardial ossifying myxoma of the right atrium in a cat

Primary cardiac neoplasms are rare in humans and animals. In humans, the mo st common primary cardiac tumor is the myxoma, which is frequently found in the left atrium. Cardiac myxoma has been reported in the dog but not in th e cat. We describe the gross, immunohistochemical, and light microscopic ex amination of a myxoma in the right atrium of a 6-year-old domestic shorthai r cat. Histologically, the tumor consisted predominantly of mesenchymal cel ls with several foci of bone and cartilage present. The tumor was encapsula ted and benign.