Choriocarcinoma in situ: a case at an early gestational stage.

A case of choriocarcinoma in situ arising in an 11 week gestational placenta is reported. Histologically, a localized nodule, measuring 5 mm, of neoplastic trophoblastic proliferation appeared to arise directly from normal stem villi and projected into the intervillous space. The tumour was composed of biphasic cytotrophoblast and syncytiotrophoblast. No fetal elements were observed. The patient had a normal full-term spontaneous vaginal delivery 22 months after curettage and was free of disease without therapy at 32 months. This tumour provides evidence for an origin of choriocarcinoma from villous trophoblast. Our report illustrates the need to perform thorough microscopic examination of the products of conception, especially in the absence of a fetus or fetal parts.