First reported case of triple benign ovarian collision tumor of the left ovary mimicking malignancy on ultrasound and CT imaging: sclerosing stromal tumor, serous cystadenoma, and fibroma

Sclerosing stromal tumor (SST) is an uncommon benign ovarian stromal neoplasm, while serous cystadenoma is one of the most frequent benign epithelial ovarian tumors. Ovarian fibroma is another benign stromal tumor that may radiologically mimic malignancy. The coexistence of these three tumors within a single ovary is exceedingly rare. We report the case of a 45-year-old woman who presented with lower abdominal pain and urinary symptoms, in whom a large left adnexal mass was detected by pelvic ultrasonography and further evaluated by contrast-enhanced computed tomography. Imaging revealed a large complex solid–cystic mass with irregular margins, raising suspicion for ovarian malignancy. Surgical excision was performed, and histopathological examination confirmed the concurrent presence of sclerosing stromal tumor, serous cystadenoma, and fibroma within the same ovary, consistent with a collision tumor. This case emphasizes the importance of careful histopathological evaluation to avoid misdiagnosis and unnecessary aggressive treatment.