Placental-site chorioma. The neoplasm of the implantation-site trophoblast.

The unusual lesion of gestational trophoblast, variously termed "placental site tumor" and "placental site trophoblastic tumor," may complicate or follow seemingly normal pregnancy, abortion or hydatidiform mole. Posing indeterminate risks of malignant behavior, those lesions must be differentiated from the banal processes of implantation-site reaction, on the one hand, and from choriocarcinoma and other poorly differentiated uterine neoplasms, on the other. A history of antecedent pregnancy, serum assay of chorionic gonadotropin and human placental lactogen, and immunohistochemical studies of tumor tissue lead to a correct diagnosis. Assessment of the degree of malignancy may be problematic in individual cases, and treatment is not always successful. With an origin in the chorionic epithelium at the implantation site, this condition may be termed "placental-site chorioma." Refined diagnostic criteria may then provide a basis for designating some lesions benign chorioma and others malignant--i.e., placental-site choriocarcinoma.