A Biologically Dominant Trophoblastic Component Guiding Neoadjuvant EMA/CO in Endometrial Carcinoma: A Clinical Case Report

Endometrial carcinoma with choriocarcinomatous components (ECCC) is a rare and aggressive malignancy for which optimal management remains undefined. We report a case illustrating how preoperative identification of a biologically dominant trophoblastic component can guide treatment sequencing and achieve durable remission. A 61-year-old postmenopausal woman presented with abnormal uterine bleeding. Endometrial biopsy revealed a mixed tumor composed predominantly of choriocarcinomatous elements with a minor grade 1 endometrioid carcinoma component. Despite only superficial myometrial invasion, imaging demonstrated multiple pulmonary nodules, and serum human chorionic gonadotropin (hCG) was markedly elevated (46,538 mIU/mL). This clinicopathological incongruity suggested that the trophoblastic component, rather than the low-grade endometrioid carcinoma, was driving disease progression. Neoadjuvant EMA/CO chemotherapy was therefore prioritized to achieve rapid systemic control. After six cycles, serum hCG normalized and pulmonary lesions completely resolved. The patient subsequently underwent total hysterectomy and bilateral salpingo-oophorectomy, which revealed no residual choriocarcinoma. She remains disease-free more than two years after completion of treatment. This case highlights the importance of recognizing clinicopathological incongruity and identifying the biologically dominant tumor component when determining treatment sequencing in rare mixed malignancies.