Choriocarcinoma in situ at a first trimester. Report of two cases indicating an origin of trophoblast of a stem villus.

Two cases of choriocarcinoma in situ arising in a first trimester placenta are reported in a 28-year-old gravida 2, para 1, Japanese woman and a 38-year-old gravida 2, para 0. Both had a dilation and curettage (D and C) for vaginal bleeding and the absence of intrauterine fetus. No macroscopic abnormalities were noted in either case. However, histologically, localized nodules of neoplastic trophoblastic proliferation measuring 5 mm in the first case, and 6 mm in the second appeared to arise directly from normal stem villi and project into the intervillous space. Both tumours were composed of biphasic cytotrophoblast and syncytiotrophoblast. Fetal elements were not observed in either case. Radiographic studies showed no metastatic lesions in either patient. Urinary human chorionic gonadotropin levels were within normal range in both patients. The first patient had a normal full-term spontaneous vaginal delivery 22 months after the D and C and was free from disease without therapy at 32 months. The second patient was free from disease without therapy with a limited follow-up. These tumours provide evidence for an origin of choriocarcinoma from trophoblast of a stem villus. This report illustrates the need to perform thorough microscopic examination of the products of conception especially in the absence of a fetus or fetal parts.