Bronchogenic cyst is a rare congenital abnormality, most commontly found in the mediastinum. Retroperitoneal location presents only 0.03% of all sites. The exact etiopathogenesis is not yet well known, it seems to be a malformation arising from the primitive foregut. RBC is generally asymptomatic and often misdiagnosed, radiological imaging help to find out the cyst and guide the diagnosis. The final diagnosis is made by histological analysis. We report a case of a 33-year-old patient with retroperitoneal bronchogenic cyst, located adjacent to the tail of pancreas and ileal loop, the imaging is misleading, reminiscent of a gastrointestinal stromal tumor, the mass was surgically completely removed, the unsuspected diagnosis was assesssed by pathology.