Mixed chorangioma and leiomyoma of the placenta, with a brief review of nontrophoblastic placental lesions.

Chorangioma is the most common type of primary non-trophoblastic tumor of the placenta, usually identified incidentally on ultrasound or at delivery. Leiomyomas within the placenta have been described, though they are rare and usually of maternal origin. We present an unusual case of a placental tumor with combined histopathologic and immunohistochemical features of both chorangioma and leiomyoma. A 39-year-old woman was found to have an echogenic placental mass at 33 weeks of gestation on ultrasound, that was thought to be a chorangioma. They followed up weekly, and performed a cesarean section at 39 weeks, due to concern for intrauterine growth restriction. No fetal or maternal complications occurred. Grossly, a 9-cm, red-brown mass with a broad-based stalk was identified on the fetal surface of the placenta near the periphery. Microscopically, the lesion was found to display characteristic features of chorangioma, with vascular proliferation, which stained positive for CD34 and CD31. SMA and caldesmon immunohistochemical staining was also positive, highlighting the proliferation of smooth muscle throughout the neoplasm. Literature review revealed a single additional case with similar characteristics.