Early duodenal signet-ring cell carcinoma covered by gastric foveolar metaplasia.

A 52-year-old man underwent esophagogastroduodenoscopy during a routine health checkup, which revealed a 15 mm semipedunculated lesion in the duodenal bulb. The initial biopsy revealed Brunner's gland hyperplasia with gastric foveolar metaplasia (GFM). A second biopsy performed 6 months later revealed signet-ring cell carcinoma (SRCC) beneath a thick overlying layer of GFM, and endoscopic mucosal resection was thus performed. The carcinoma was confined to the mucosa only. Both the SRCC and the overlying GFM exhibited a gastric-type phenotype, with an in situ lesion identified within the GFM. We report a diagnostically informative case of early duodenal SRCC.