A Rare Case of Mixed Malignant Ovarian Germ Cell Tumor Composed of Immature Teratoma and Yolk Sac Tumor

Malignant ovarian germ cell tumors (MOGCTs) are rare but aggressive neoplasms, accounting for a small percentage of ovarian cancers, and often affect young women. We present the case of a 23-year-old woman who presented to the clinic believing she was 14.2 weeks pregnant. However, she was found to have elevated beta-human chorionic gonadotropin (β-hCG) levels and a complex left adnexal mass. Initial ultrasound suggested an ovarian tumor, and surgical exploration revealed a large mixed germ cell tumor measuring 36.5 x 27 x 23.9 cm, weighing 9463.2 grams, with metastases to the small bowel, omentum, and peritoneum. Final pathology confirmed a high-grade immature teratoma and yolk sac tumor with a composition of 60% teratoma and 40% yolk sac tumor (YST). The patient underwent comprehensive staging surgery, including omentectomy, bowel resection, and lymphadenectomy, followed by four cycles of bleomycin, etoposide, and cisplatin (BEP) chemotherapy. Unfortunately, the patient has not responded to the standard chemotherapy regimen of BEP and will pursue further treatment through clinical trials. This case highlights the diagnostic challenge of MOGCTs, particularly mixed forms, which may present with nonspecific symptoms. Timely diagnosis and aggressive treatment, including fertility-preserving surgery when possible, are crucial for improving outcomes. Although survival rates are generally favorable, close follow-up is needed due to the potential for relapse, particularly in cases with advanced disease, as seen in our case. This case emphasizes the importance of considering MOGCTs in young women with elevated β-hCG and adnexal masses and the management of this metastatic disease.