Mature cystic teratoma at a cesarean-scar uterine isthmus: a case report and literature review

Mature cystic teratomas (MCTs) represent common ovarian germ cell neoplasms; primary uterine teratomas are exceedingly uncommon. We report an extremely rare MCT arising within a cesarean-section scar at the anterior uterine isthmus and summarize the key imaging clues and follow-up considerations. A 41-year-old woman presented with persistent postmenstrual brown vaginal discharge for over six months. Transvaginal ultrasonography and pelvic magnetic resonance imaging (MRI) revealed a heterogeneous mass within the anterior uterine isthmus at the site of a prior cesarean scar. Hysteroscopic examination identified multiple filamentous whitish hair-like structures and yellow-white caseous/sebaceous material adjacent to a firm spherical mass. Histopathological analysis confirmed the diagnosis of a mature cystic teratoma, demonstrating keratinized squamous epithelium, hair shafts, focal calcification, and keratinous debris. The mass was completely excised by hysteroscopic resection under laparoscopic monitoring. This case underscores that although uterine teratomas are uncommon, they should be included in the differential diagnosis of atypical isthmic masses, especially those occurring at cesarean scar sites. Ultrasound remains the first-line imaging modality, whereas MRI is particularly useful for demonstrating intralesional fat and refining the differential diagnosis. Complete excision followed by structured surveillance is important for achieving favorable outcomes.