A rare case of a giant cystic leiomyoma presenting as a retroperitoneal mass.

Background: Giant retroperitoneal uterine leiomyomas are uncommon. Degenerative changes of a leiomyoma may lead to unusual presentation resulting in misdiagnosis preoperatively. The final diagnosis can be made either intraoperatively or histologically.

Case: We report a 45-year-old multiparous women presented with abdominal distension and fatigue for six months. Abdominopelvic Sonography and computed tomography showed a large cystic mass that filled the pelvis and abdomen. With the preoperative diagnosis of a malignant tumor, a laparotomy was planned. Intraoperatively, a cystic mass originated from the uterus near the left side of the broad ligament extending to the retroperitoneal space was observed. Total hysterectomy and bilateral salphingo-oopherectomy was administered. The histology revealed a leiomyoma with cystic degeneration.

Conclusion: Retroperitoneal leiomyomas should be kept in mind in the diferrential diagnosis of a giant cystic mass in abdomen.