Precise preoperative diagnosis of struma ovarii with pseudo-Meigs' syndrome mimicking ovarian cancer with the combination of 131 I scintigraphy and 18 F-FDG PET: case report and review of the literature.

BACKGROUND: Struma ovarii is a rare ovarian neoplasm that often appears malignant on conventional imaging. Pseudo-Meigs' syndrome with ascites, pleural effusion, and elevated serum CA 125 levels is much rarer and leads to misdiagnosis of ovarian cancer and unnecessary extended surgery.

CASE PRESENTATION: A 50-year-old woman with abdominal distention and dyspnoea was referred to our hospital. Ultrasound, computed tomography (CT), and magnetic resonance imaging (MRI) showed a polycystic ovarian tumor with a solid component, pleural effusion, and massive ascites with negative cytology. Her serum CA 125 level was 1237 U/ml, indicating the presence of ovarian cancer. Based on increased uptake of 131 I but no uptake of 18 F-FDG in the tumor, the preoperative diagnosis was struma ovarii with pseudo-Meigs' syndrome, which was confirmed histologically. She had no evidence of ascites and pleural effusion six months after surgery.

CONCLUSIONS: To date, there have been no systematic reviews focused on preoperative diagnosis with imaging modalities. The combination of 131 I scintigraphy and 18 F-FDG PET/CT in addition to conventional imaging modalities can provide the precise preoperative diagnosis of struma ovarii with pseudo-Meigs' syndrome mimicking ovarian cancer, leading to the appropriate treatment strategy.