Metastasis and the Primary Tumor Were Barely Indistinguishable in a Patient with Pulmonary Choriocarcinoma: a Case Report

Abstract

Background. In female patients, choriocarcinoma most commonly occurs from the trophoblasts and is associated with gestation. Primary pulmonary choriocarcinomas are very rare. We herein report a case of pulmonary choriocarcinoma in which the primary tumor was barely distinguishable from a metastatic tumor. Case. A 36-year-old woman who underwent an induced abortion due to a partial hydatidiform mole between two normal pregnancies was referred to our hospital because of a well-defined mass shadow (26×21 mm) in the lower lobe of the right lung. She developed amenorrhea one month later, and a pregnancy test was positive. She was referred for a gynecological examination at our hospital on the suspicion of an extrauterine pregnancy after a sonographic examination did not reveal an embryo. Although a high serum level of human chorionic gonadotrophin (hCG) was found, a gynecological examination revealed no pelvic abnormalities. Tumor enlargement was found on a chest roentgenogram two months later (31×25 mm). Bronchofiberoscopy did reveal any malignancy. The high uptake of FDG in the tumor was observed on PET-CT. A malignant tumor was strongly suspected; thus, lower lobectomy of the right lung was performed. The tumor was microscopically and immunohistochemically diagnosed as a choriocarcinoma. The postoperative serum hCG level dropped to normal levels, and adjuvant chemotherapy consisting of methotrexate, etoposide and actinomycin D was administered three times. Recurrence has not been observed in the year after surgery. The tumor was first diagnosed as being metastasis from the hydatidiform mole. It was difficult to diagnose as a primary pulmonary choriocarcinoma because there were no other tumors in the lung, and there were no apparent primary lesions in the pelvic cavity. We clinically concluded that the tumor was derived from trophoblasts, because the low frequency of primary pulmonary choriocarcinoma as well as her history of pregnancy. Thus, the tumor was considered to have originated from the chorionic tissue in normal pregnancy, not from the hydatidiform mole, due to the normal serum hCG level after the abortion of the mole.