Rare Intraoperative Presentation of a Coexistent Uterine Cystic Mass and Bilateral Ovarian Cystic Masses.

Uterine cystic lesions are commonly encountered in clinical practice, but serosal cysts, such as uterine serous cystadenomas, are exceedingly rare. This case report highlights the rare occurrence of a large uterine serous cystadenoma, initially misdiagnosed as an ovarian cyst on preoperative imaging and later discovered intraoperatively to be an exophytic cystic mass arising from the uterus. It underscores the diagnostic challenge of differentiating large exophytic uterine cystic masses from ovarian cystic masses in patients with distorted anatomy on preoperative imaging. A 50-year-old postmenopausal woman, with no significant past medical or surgical history, was referred for incidental bilateral ovarian cysts detected on CT imaging due to abdominal pain. Transvaginal ultrasound confirmed the cysts, and tumor markers were within normal limits. Given her postmenopausal status, a bilateral salpingo-oophorectomy was planned. During surgery, a 15 cm cyst was found arising from the uterine fundus instead, along with multiple simple cysts on the uterus and small bilateral ovarian cysts. The patient underwent cyst aspiration and excision of the uterine cyst, along with bilateral salpingo-oophorectomy. A hysterectomy was considered due to potential malignancy risk, but was deferred after benign findings on frozen section. Final pathology confirmed a benign Müllerian cyst consistent with serous cystadenoma, with no evidence of malignancy. This case illustrates the importance of intraoperative frozen section analysis and highlights the need for thorough preoperative imaging to guide surgical decisions.