Giant mucinous cystic adenoma with pancreatic atrophy mimicking dorsal agenesis of the pancreas.

Mucinous cystic adenoma (MCA) of the pancreas is a rare benign cystic tumor with ovarian-like stroma and lack of communication with the pancreatic ductal system. The ovarian tissue is incorporated from the left gonad within the dorsal pancreas during embryogenesis. Consequently, congenital dorsal agenesis of the pancreas (DAP) cannot be associated with MCA. We report the case of a giant MCA associated with atrophy of the dorsal pancreas mimicking complete DAP. Pancreato-magnetic resonance imaging failed to identify the dorsal pancreas but the absence of diabetes mellitus and compression of the splenic vein with major tributaries rectified the diagnosis of secondary atrophy of the distal pancreas. Unusual proximal location of the cyst in the pancreas may have induced chronic obstruction of both the dorsal pancreatic duct and the splenic vein, with secondary atrophy of the distal pancreas.