Abstract
Choledochocele is a rare subtype of choledochal cyst and is associated with increased prevalence of periampullary cancers. Here, we report an unusual manifestation of infiltrative duodenal cancer arising from a choledochocele, involving superficial spreading (muscularis mucosae) of cancer cells along the duodenum causing gastric outlet obstruction, which clinically mimicked superior mesenteric artery syndrome. Histologically, wide spread of cancer cells was confirmed from periampullary region to duodenojejunal junction showing mismatch with radiologic findings, in which the cancer segment was mainly located in the distal duodenum. Clinical, radiologic, and pathologic findings are discussed with literature reviews.