Primary retroperitoneal mucinous cystic tumor with borderline malignancy: a case report and review of the literature.

Primary retroperitoneal mucinous cystic tumor (PRMCT) is rare and preoperative diagnosis is challenging due to their rarity, lack of specific diagnostic imaging, clinical presentation, and tumor markers. We present an extremely rare case of PRMCT of borderline malignancy and summarize the characteristics of previously reported cases. Although the prognosis and optimal therapeutic strategies require further investigation due to its rarity, we should be considered when dealing with retroperitoneal cystic lesions.