Massive Ovarian Fibrothecoma Mimicking Advanced Ovarian Cancer in a High-Risk Patient: Diagnostic Challenges and Selective Use of Preoperative Biopsy.

Background: Ovarian fibrothecoma is a rare benign sex cord-stromal tumor that may be misdiagnosed as ovarian malignancy because of nonspecific clinical, radiologic, and serologic findings. Percutaneous biopsy in suspected ovarian malignancy is controversial and is generally reserved for unresectable disease, neoadjuvant chemotherapy planning, poor surgical candidates, or when histological confirmation is required before treatment.Massive ovarian fibrothecoma complicated by Meigs' syndrome and severe multi-organ dysfunction is extremely uncommon and may create substantial diagnostic and therapeutic challenges, particularly in medically high-risk patients. In addition, interpretation of tumor markers such as human epididymis protein 4 (HE4) may be confounded by renal dysfunction, further complicating preoperative assessment. Case Presentation: A 59-year-old postmenopausal woman presented with progressive abdominal distension and dyspnea. Imaging revealed a massive cystic-solid pelvic mass with extensive ascites, pleural effusion, lymphadenopathy, and peritoneal thickening, raising strong suspicion for advanced ovarian cancer. Serum CA125 and HE4 levels were markedly elevated; however, the patient also had significant renal dysfunction, which may have contributed to HE4 elevation. The patient subsequently developed severe systemic compromise, including respiratory failure, cardiac insufficiency, renal impairment, hypoxemia, resulting in poor surgical tolerance. Following multidisciplinary evaluation and preoperative optimization, ultrasound-guided core needle biopsy and intraoperative frozen section supported the diagnosis of ovarian fibrothecoma. A giant right ovarian tumor measuring approximately 45 cm was completely resected. Postoperatively, pleural effusion and ascites resolved, and organ function gradually improved, consistent with Meigs' syndrome. Conclusion: This case highlights that massive ovarian fibrothecoma with Meigs' syndrome may closely mimic advanced ovarian cancer and lead to life-threatening multi-organ dysfunction. Benign ovarian stromal tumors should remain in the differential diagnosis of giant adnexal masses with pleural effusion, ascites, and elevated tumor markers. In carefully selected high-risk patients with diagnostic uncertainty and poor surgical tolerance, preoperative image-guided biopsy may provide useful histopathologic information to support individualized management after multidisciplinary assessment. Core Tip: We report a rare case of massive ovarian fibrothecoma with Meigs' syndrome and multi-organ dysfunction closely mimicking advanced ovarian cancer. This case highlights the diagnostic challenges associated with giant adnexal masses accompanied by ascites, pleural effusion, lymphadenopathy, and elevated tumor markers. In carefully selected high-risk patients with high diagnostic uncertainty and poor surgical tolerance, after multidisciplinary assessment, preoperative ultrasound-guided biopsy may provide useful histopathologic information to support individualized multidisciplinary management and help avoid inappropriate treatment.