Pelvic Müllerian duct cyst with coexisting endometriosis: a case report

BACKGROUND: Müllerian duct cyst (MDC) is an uncommon congenital lesion arising from incomplete regression of the paramesonephric duct. It typically presents as a midline pelvic cystic lesion and is often asymptomatic, making preoperative diagnosis challenging. CASE PRESENTATION: We report the case of a 37-year-old woman who was admitted in 2024 for evaluation of an incidentally discovered pelvic cystic lesion. Pelvic magnetic resonance imaging (MRI) revealed a well-circumscribed, non-enhancing posterior pelvic cystic lesion. Laparoscopic resection of the cyst was performed, and intraoperatively, dense adhesions were noted between the cyst, the posterior uterine wall, and the posterior peritoneum. Histopathological examination confirmed the diagnosis of MDC and revealed coexisting endometriosis in the adherent posterior peritoneum. CONCLUSIONS: This case highlights the importance of considering MDC in the differential diagnosis of pelvic cystic lesions in women, as well as the potential coexistence of endometriosis.