Thymoma with suspected secondary myocardial infarction in a red panda.

A 17-y-old, female red panda (Ailurus fulgens) with unusual restlessness and a poor prognosis was euthanized and submitted for autopsy. Postmortem examination revealed a large cystic mass within the cranial mediastinum that severely compressed the lung. Histologic analysis classified the mass as a thymoma with abundant small lymphocytes and recognizable type B2 epithelial cells. Additionally, the heart had several chronic myocardial infarcts within the left ventricular free wall and septum. Granulomatous lymphadenitis and prominent anthracosilicosis were noted in the tracheobronchial lymph nodes. Secondary findings included interstitial nephritis, splenic myelolipoma, dental attrition, endocardiosis, and ulcerative gastritis. Expansile thymomas are known to cause myocardial infarction with nonobstructive coronary arteries. We propose a similar pathogenesis in this case.