Intraplacental choriocarcinoma arising in a second trimester placenta with partial hydatidiform mole.

We report a well-documented case of a 28-year-old woman, gravida 3, para 1, undergoing termination at 22 weeks for fetal congenital malformations with concurrent partial hydatidiform mole and choriocarcinoma. A fetal ultrasound showed spina bifida, and an elective termination was performed. One month later, the patient presented with vaginal bleeding, cough, and shortness of breath. A chest computed tomographic scan revealed multiple lung nodules. A pelvic ultrasound was consistent with retained products of conception, and endometrial sampling showed an atypical trophoblastic proliferation consistent with choriocarcinoma. The serum beta-human chorionic gonadotropin level was greater than 100,000 IU/mL. The placental pathology reviewed at our institution showed microscopic foci of choriocarcinoma arising in a partial hydatidiform mole. Flow cytometry performed on paraffin-embedded tissue showed a triploid peak, which confirmed the partial molar nature of this gestation. Immunohistochemistry showed nuclear p57 expression in the partial molar villous trophoblastic and stromal cells, but not in the severely atypical trophoblasts, further supporting the diagnosis of intraplacental choriocarcinoma distinct from the partial mole. Although the molecular pathogenesis remains to be elucidated, this report provides additional evidence that choriocarcinoma may arise directly from partial molar gestations. Moreover, it emphasizes the importance of thorough sampling of placentas with partial hydatidiform mole in search of minute foci of choriocarcinoma because they might represent a potential source of metastatic gestational trophoblastic disease.