Malignant placental site trophoblastic tumor. A case report and a review of the literature.

A clinicopathological and immunohistochemical study of a fatal case of placental site trophoblastic tumor (PSTT) is presented. PSTT is a rare variant of trophoblastic disease. Histologically the tumor is characterized by a monomorphic cell population, derived from the extravillous intermediate trophoblast. The tumor cells contain human placental lactogen (HPL) as the predominant marker, while human chorionic gonadotropin (HCG) is present only locally. PSTT has a malignant potential. In the case presented the tumor finally developed the biphasic pattern of choriocarcinoma. The clinical and pathological features of the malignant PSTT are reviewed. Establishing the diagnosis and predicting the biologic behavior of PSTT may be difficult. If metastases occur the prognosis is poor regardless of therapeutic intervention.