A Patient with Duodenal Mucinous Adenocarcinoma Presenting as a Laterally Spreading Tumor

Primary duodenal carcinoma is rare. Duodenal mucinous adenocarcinoma (DMA) is even rarer, and its associated manifestations and typical endoscopic or imaging findings are not well characterized. Herein, we report a case of primary DMA in an asymptomatic 58-year-old man who visited our hospital for a regular health screening. Upper endoscopy revealed an approximately 4-cm lesion in the second portion of the duodenum, but the mass was not visualized on computed tomography. Biopsies revealed a tubular adenoma that was subsequently resected. Frozen biopsies demonstrated DMA with a background of low-grade tubular adenoma for which we performed Roux-en-Y duodenojejunostomy and jejunojejunostomy. To our knowledge, this is the first report of a patient with DMA in Korea.