Silent giant: a 35-cm mucinous ovarian cystadenoma presenting as failure to lose weight

Giant ovarian mucinous cystadenomas have become uncommon due to earlier detection, yet they may closely mimic malignancy on imaging. We report a 45-year-old woman with progressive abdominal enlargement and inability to lose weight, who remained otherwise asymptomatic. Imaging revealed a multiloculated right adnexal mass with thick septations and apparent solid components, associated with minimal ascites and right grade III hydronephrosis. Based on imaging features, the mass was classified as O-RADS 5, while serum tumor markers were within normal limits. Exploratory laparotomy demonstrated a 35-cm right ovarian mass with marked anatomical distortion and dense Zühlke grade IV adhesions. The tumor was removed intact to avoid spillage, and intraoperative frozen section analysis confirmed benign pathology, guiding continuation of the planned procedure. Final histopathology revealed a benign mucinous cystadenoma. Postoperative recovery was uneventful. This case highlights the limitations of imaging in giant ovarian tumors and underscores the importance of a safety-oriented surgical approach.