Serous Borderline Tumor Originating From a Paratubal Cyst in a 22-Year-Old Woman: A Case Report and Review of the Literature.

Serous borderline tumors (SBTs) typically arise from the ovary, and their development within a paratubal cyst is an uncommon occurrence. We report a 22-year-old nulliparous woman with chronic dysmenorrhea and an enlarging right adnexal cyst who underwent laparoscopic bilateral salpingectomy for symptom relief and sterilization. Intraoperatively, a 5 cm right paratubal cyst was identified, with normal uterus and ovaries. Histopathologic examination revealed an SBT confined to the paratubal cyst (International Federation of Gynecology and Obstetrics stage IA (FIGO IA)). This case highlights that even small, radiologically benign-appearing paratubal cysts can harbor borderline neoplasia. Awareness of this rare entity and careful histopathologic evaluation of all adnexal cysts are essential for accurate diagnosis and optimal management in young women.