- Placental site trophoblastic tumor (PSTT) is a rare variant of gestational trophoblastic disease that originates from the implantation site intermediate trophoblast. We report four patients with PSTT and review pertinent literature. Three patients presented with disease confined to the uterus and one patient with disease extension beyond the uterus. Antecedent pregnancy was full-term pregnancy in three patients and termination of a 21-week pregnancy in one patient. Interval from the antecedent pregnancy was <1 year in three patients and 13 years in one patient. Primary treatment was simple hysterectomy in three patients and radical hysterectomy in one patient. Overall, three patients received chemotherapy; one had EP/EMA as adjuvant chemotherapy, one had EMA/CO for rising levels of serum beta-hCG and one had BEP then VIP for recurrent disease. The three patients with disease confined to the uterus have remained after treatment alive and with no evidence of disease, whereas the one patient with disease extension beyond the uterus died of disease despite surgery and aggressive chemotherapy. It is concluded that disease extension beyond the uterus is the most important adverse prognostic factor. Other adverse prognostic factors are interval from antecedent pregnancy >2 years, age >40 years, and mitotic count >5 mitotic figures/10 high-power fields. Because of the relative insensitivity to chemotherapy, hysterectomy is the mainstay of treatment. EP/EMA seems to be the most effective first-line chemotherapy available to date for metastatic and relapsing PSTT.