Giant cystic leiomyoma of the uterus occupying the retroperitoneal space.

A 31-year-old nulliparous woman visited our hospital complaining of abdominal distension. Abdominal ultrasonography and computed tomography revealed a 40 × 40 × 30-cm, multilocular cystic mass extending from the upper abdomen to the pelvis. Magnetic resonance imaging (MRI) revealed a cystic tumor that was hypointense on T1-weighted images and was heterogeneously hyperintense on T2-weighted images. The final diagnosis was an 8 kg leiomyoma with cystic degeneration. Uterine leiomyomas are common benign tumors in females of reproductive age. However, subserosal leiomyomas with complete cystic degeneration of the retroperitoneal space are rare, and they are difficult to accurately diagnosis without pathological examination.