Incidental finding of placental choriocarcinoma after an uncomplicated term pregnancy: a case report with review of the literature.

Choriocarcinoma is frequently preceded by a complete mole, ectopic pregnancy, nonmolar intrauterine abortion, and uncommonly by a partial mole. Choriocarcinoma coexisting with or after an otherwise "normal" pregnancy is extremely rare, with an estimated occurrence of 1 per 160,000 pregnancies. We here report a case of a placental choriocarcinoma with no metastases in a full-term intrauterine pregnancy. The patient is a 29-year-old gravida 2 para 1 female, who had an uncomplicated full-term vaginal delivery of a healthy 3030 g female infant. Her current pregnancy was uneventful, and past medical history was significant for an elective termination of pregnancy 2 years ago at 8 weeks of gestation. Routine examination of the placenta showed a gray-tan nodule, measuring 2 cm in the largest dimension, with a papillary cut surface. Microscopically, this nodule was composed of highly atypical cytotrophoblastic cells and multinucleated atypical syncytiotrophoblastic cells, which were positive for beta-human chorionic gonadotrophin by immunostaining. Extensive necrosis and multiple foci of hemorrhage were present. The overall morphologic and immunohistochemical features were diagnostic for choriocarcinoma. Further investigations, including a full body computed tomography scan, showed no lesions suspicious for metastases. The patient is currently asymptomatic and being followed-up with monthly beta-human chorionic gonadotrophin levels, the most recent one being negative. By reporting this case and reviewing the literature, we support the opinion of a recent similar case report that the incidence of placental choriocarcinoma may actually be higher than expected, as placental examination after a normal spontaneous delivery is not routinely performed at most of the institutions.