A large retroperitoneal cystic venous malformation mimicking bilateral ovarian cystic tumors

Retroperitoneal cysts are a rare disease. Most retroperitoneal cysts of vascular origin have been reported as hemangiomas. However, according to the recent classification of vascular anomalies accepted by the International Society for Study of Vascular Anomalies (ISSVA), these previously reported retroperitoneal hemangiomas should rather have been classified as vascular malformations. A 65-year-old woman visited our hospital complaining of a sense of unexplained abdominal fullness. Magnetic resonance imaging suggested a uterine leiomyoma and bilateral ovarian cystic tumors. However, abdominal surgery revealed normal bilateral ovaries, but huge cystic masses in the retroperitoneum. Postoperative histological diagnosis of the retroperitoneal cysts demonstrated that they were venous malformations. This is a rare case in which large cystic retroperitoneal venous malformations were preoperatively diagnosed as ovarian cystic tumors. Retroperitoneal hemangiomas should be renamed as vascular malformations following the ISSVA classification.