Abstract
BACKGROUND: Retroperitoneal non-pancreatic or idiopathic pseudocysts are very rare lesions. This case report aimed to present our patient and to check all the available literature on this kind of rare disease. CASE PRESENTATION: Our patient was a 67-year-old Iranian man admitted with mild abdominal discomfort for three months. Ultrasonography and CT scan revealed a huge cystic structure within the retroperitoneal space. The lesion was excised through midline laparotomy and opening of the retro-peritoneum. The histopathology of the cyst wall revealed a benign cystic lesion with no epithelial lining. A histologic diagnosis of non-neoplastic retroperitoneal pseudocyst was made. CONCLUSION: The primary non-pancreatic retroperitoneal pseudocysts are rare lesions and have to be distinguished from other differential diagnoses of retroperitoneal lesions, and a surgeon should be aware of the possible occurrence of these lesions with unknown origin. Surgical excision is the only way to exclude malignancy and confirm the diagnosis.