Placental-site trophoblastic tumor of the uterus. Clinicopathological and immunohistochemical observations of a case.

The clinicopathological features of a 28-year-old woman with placental-site trophoblastic tumor (PSTT) are described. The patient presented with severe proteinuria and was found to have a cystic uterine tumor. The serum beta-human chorionic gonadotropin (hCG) level was only slightly elevated. The tumor extended to the serosa without gross metastasis, and was resected. The specimen was composed of active intermediate trophoblasts (IT) and degenerative or inactive ITs. The former component had round to oval and vesicular nuclei, and abundant amphophilic or lightly eosinophilic cytoplasm. The latter component had irregular-shaped pyknotic nuclei and deeply eosinophilic cytoplasm. However, the tumor lacked the bilaminar (cyto- and syncytiotrophoblastic) structure that is a characteristic feature of choriocarcinoma. Immunohistochemical evaluation with human placental lactogen (hPL) and hCG antisera revealed that most of the tumor cells contained abundant hPL, whereas only a small number of cells contained hCG. This method seemed to be most helpful for the differential diagnosis of PSTT from other trophoblastic tumors or non-trophoblastic uterine tumors, and also to be useful for determining the prognostic behavior of PSTT.