Extrauterine Leiomyoma of the Sigmoid Colon Mimicking an Adnexal Mass

Leiomyomas are benign smooth muscle tumors that typically arise in the uterus but can also occur in less common locations such as the cervix, vagina, broad ligament, or gastrointestinal tract. Extrauterine leiomyomas are rare and can be difficult to localize with imaging. We present a case of a 38-year-old woman with a left pelvic mass that was initially suspected to be ovarian in origin based on computed tomography and ultrasound images. However, diagnostic laparoscopy revealed a well-circumscribed mass originating from the sigmoid colon mesentery. Final histopathological analysis confirmed the mass to be a benign extrauterine leiomyoma. This case highlights the diagnostic challenge of differentiating pelvic masses and underscores the importance of maintaining a broad differential diagnosis when evaluating adnexal masses.