Spontaneous Leiomyomas of the Gastroesophageal Junction in a Chimpanzee (Pan troglodytes)

A 49-y-old, female chimpanzee presented with a history of cardiac failure. Postmortem examination revealed lesions consistent with congestive heart failure and 2 incidental, round, firm, pale-tan intramural nodules (diameter, 2 cm) in the stomach at the gastroesophageal junction (GEJ). Histologically, the GEJ nodules were diagnosed as benign spindle-cell tumors. Immunohistochemical evaluation revealed neoplastic cells diffusely labeled with α-smooth muscle actin and vimentin, multifocally labeled for desmin, and were negative for c-kit (CD117). Electron microscopy revealed intracytoplasmic bundles of myofilaments with dense bodies, basal lamina, and few pinocytic vesicles in the neoplastic cells. According to these findings, leiomyomas of the GEJ were diagnosed. Gastrointestinal stromal tumors have been documented to occur in chimpanzees, but there are no reports of GEJ leiomyomas. To our knowledge, this report is the first description of spontaneous leiomyomas of the GEJ in a chimpanzee.