An Unusual Site of Mature Cystic Teratoma in the Fallopian Tube: A Rare Case Report.

Background: Mature cystic teratoma (MCT) is a common benign ovarian germ cell tumor; however, its occurrence in the fallopian tube or paratubal region is exceedingly rare. Preoperative diagnosis is challenging due to nonspecific clinical and imaging findings, often mimicking an ovarian cyst. Case Illustration: A 34-year-old nulliparous woman presented with severe cyclical left lower abdominal pain and a progressively enlarging abdominal mass. Preoperative evaluation suggested a dermoid cyst with bilateral endometriomas. Intraoperatively, revealed a large cyst arising from the left fallopian tube, and histopathology confirmed a mature cystic teratoma with bilateral ovarian endometriomas. This rare case highlights the diagnostic challenge of tubal mature cystic teratoma. Conclusion: Fallopian tube mature cystic teratoma should be considered in the differential diagnosis of complex adnexal masses. Definitive diagnosis relies on intraoperative assessment and histopathological confirmation, particularly in patients with coexisting pelvic pathology.