Uterine epithelioid trophoblastic tumor in an African green monkey (Chlorocebus aethiops sabaeus)

A uterine mass was detected on physical exam in a multiparous African green monkey as an incidental finding, and the well-circumscribed mass was removed via hysterectomy. Histologically, the mass consisted of sheets, nests, and cords of uniform intermediate trophoblastic cells with eosinophilic or clear cytoplasm. These neoplastic cells aggregated around blood vessels, forming islands of viable tumor cells amid extensive areas of coagulative necrosis with calcification in a 'geographic' pattern of necrosis. Immunohistochemistry of the trophoblastic cells revealed strong and diffuse staining for pancytokeratin AE1/3 and p63, with weak and moderate staining for human placental lactogen and placental alkaline phosphatase, respectively. Immunohistochemical staining for smooth muscle actin, epithelial membrane antigen, and human chorionic gonadotropin was negative. Overall, the histologic and immunohistochemical features of this tumor were consistent with those of epithelioid trophoblastic tumor. This rare tumor type has not been reported previously to occur in African green monkeys.