BACKGROUND: Placental site trophoblastic tumor is a rare form of gestational trophoblastic disease that commonly presents with vaginal bleeding and amenorrhea after pregnancy. CASE: A women with a normal gestation at 37 weeks presented with a pneumothorax. The patient underwent placement of a chest tube and a subsequent thorascopic pulmonary bullous resection for persistence of the pneumothorax. Histological examination of the specimen revealed a metastatic placental site trophoblastic tumor. CONCLUSION: Gestational trophoblastic disease must be considered in the differential diagnosis of pneumothorax during pregnancy.