Uterine choriocarcinoma arising from serous carcinoma in a postmenopausal woman: an analysis of next-generation sequencing and PD-L1 immunochemistry

BACKGROUND: Uterine somatic choriocarcinoma is a rare, clinically aggressive malignant tumor. They frequently concur with other cancer. However, the molecular pathogenesis between somatic choriocarcinoma and the concurrent carcinoma has rarely been addressed to date. CASE PRESENTATION: We report a 68-years old Chinese woman with a uterine choriocarcinoma arising from serous carcinoma. The patient underwent radical surgery including total abdominal hysterectomy with bilateral salpingo-oophorectomy, omentectomy and pelvic lymph node resection. She received 10 courses of post-operative chemotherapy. She died of disease 13 months after her surgery. Microscopically, the tumor showed a biphasic pattern of choriocarcinoma and serous carcinoma. The choriocarcinomatous component showed a combination of cytotrophoblast, intermediate trophoblast and syncytiotrophoblast with hemorrhage and necrosis. The component of serous carcinoma was characterized by solid sheets of small cells with marked nuclear atypia and occasional glandular and papillary formation. PD-L1 was exclusively expressed in the choriocarcinomatous component. Next-generation sequencing revealed that the genetic abnormalities were overlapping between the two components.