Placental site trophoblastic tumor--a challenging rare entity.

Placental site trophoblastic tumor (PSTT) is a challenging rare variant of gestational trophoblastic disease (GTD) with variable characteristics. Historically, it was first described in 1895 and was considered a benign lesion until Scully and Young recognized its malignant potential in 1981. Current knowledge related to PSTT is largely based on the experience of handling this disease in established trophoblastic disease centers and on the experience of authors who reported small series or singular cases. In contrast to other forms of GTD, it arises from the implantation-site intermediate trophoblast, produces less beta-hCG and is less sensitive to chemotherapy. More than half of the patients present with disease confined to the uterus, whereas the remainder present with disease extension beyond the uterus. Because of the relative insensitivity to chemotherapy, simple hysterectomy is the mainstay of treatment. While the outcome of patients with disease confined to the uterus is usually excellent, most patients with disease extension beyond the uterus experience progression of disease and die despite surgery and aggressive chemotherapy. Other important adverse prognostic factors are interval from antecedent pregnancy > 2 years, age > 40 years and mitotic count > 5 mf/10 HPF Although the ideal chemotherapy regimen for PSTT has yet not been established, it seems that the EP/EMA regimen is the most effective first-line chemotherapy available to date for metastatic and relapsing PSTT. Although PSTT produces less hCG than choriocarcinoma, beta-hCG is still the best available serum marker to follow the disease and treatment course of PSTT.