Presence of Chorionic Villi Does Not Exclude Choriocarcinoma: A Case Report of Early Choriocarcinoma Associated with a Complete Hydatidiform Mole.

Background: Gestational choriocarcinoma is a highly aggressive trophoblastic neoplasm. Historically, the presence of chorionic villi was considered discordant with the diagnosis of choriocarcinoma. We report a case of early gestational choriocarcinoma arising in a post-molar setting with residual chorionic villi, creating a diagnostic pitfall. Case report: a 51-year-old woman with a prior complete hydatidiform mole showed plateauing β-human chorionic gonadotropin (ß-hCG) levels. She underwent total laparoscopic hysterectomy. Histologic examination of the uterine mass revealed a malignant biphasic-to-triphasic trophoblastic proliferation with marked atypia, brisk mitotic activity, extensive hemorrhage, and necrosis, situated immediately adjacent to a single residual molar villus. Immunohistochemistry showed strong β-human chorionic gonadotropin expression in syncytiotrophoblasts, a elevated Ki-67 index (∼80%), focal human placental lactogen (hpL) expression, and absence of p63 staining, confirming choriocarcinoma and excluding other trophoblastic tumors. Conclusion: this case demonstrates that the presence of chorionic villi does not exclude a diagnosis of choriocarcinoma and underscores the necessity of rigorous clinicopathologic correlation.