PLACENTAL SITE TROPHOBLASTIC TUMOR - WITH FEATURES BETWEEN AN EXAGGERATED PLACENTAL SITE REACTION AND A PLACENTAL SITE TROPHOBLASTIC TUMOR

Chorionic villi, whose presence in cases of trophoblastic disease is normally used to exclude both a choriocarcinoma and placental site trophoblastic tumor (PSTT), were present in the initial uterine curettage specimen of a trophoblastic tumor. The lesion shared morphologic features of both an exaggerated placental site reaction and a PSTT. There was infiltration of the posterior wall of the uterus by small clusters and isolated cells which had a prominent affinity for vessels and resembled a usual placental bed reaction. There was, however, deep involvement of myometrium with extension to the cervix, and the condition persisted for 5 months after uterine evacuation. Because different treatment is entailed, identification of this lesion as a tumor of nonvillous trophoblast is also of great importance in a region where the more usual forms of trophoblastic disease represent a declining but not infrequent event. When products of gestation are examined, the possibility of a PSTT should be considered and the clinician alerted if there is a suggestion of excessive intermediate trophoblastic activity, regardless of the presence of chorionic villi. While this may result in the unnecessary followup of some cases, it would permit, with the aid of serial β-hCG and HPL levels, the earlier detection of PSTTs. © 1990 International Society of Gynecological Pathologists.