An Unclassifiable Malignant Ovarian Germ Cell Tumor With Focal Choriocarcinoma-Like Features: A Case Report With Diagnostic Ambiguity and Adjuvant Treatment Considerations

Malignant ovarian germ cell tumors (MOGCTs) are uncommon neoplasms with substantial histologic diversity. Although most tumors can be assigned to established subtypes, some tumors show overlapping morphologic and immunophenotypic findings that complicate classification and management. We report a 37-year-old nulligravid woman with a right ovarian tumor, massive ascites, and elevated serum human chorionic gonadotropin (hCG). Histopathological examination revealed heterogeneous findings, including focal yolk sac tumor-like morphology and focal choriocarcinoma-like differentiation. Tumor cells were positive for AE1/AE3 and glypican-3, while AFP, SALL4, OCT4, and CD30 were negative; scattered cells were positive for hCG, GATA3, and p57. The tumor was diagnosed as an unclassifiable malignant ovarian germ cell tumor, International Federation of Gynecology and Obstetrics (FIGO) stage IC1. A key management issue was the postoperative intensity of bleomycin, etoposide, and cisplatin (BEP) chemotherapy. Because of incomplete formal staging and persistent histologic ambiguity, four cycles of BEP were selected rather than treatment de-escalation. The patient remains disease-free on follow-up. This case highlights the following two practical lessons: unusual ovarian germ cell tumors may remain unclassifiable despite integrated pathology, and adjuvant treatment decisions in stage I disease may depend not only on stage but also on staging adequacy and biologic uncertainty.