Superficially elevated-type serrated hyperplastic lesion of the stomach with minute adenocarcinoma.

We report a case of gastric serrated hyperplastic lesion with minute adenocarcinoma. A 65-year-old Japanese man underwent endoscopic submucosal dissection to the superficially elevated-type (0-IIa) lesion located at the lesser curvature of the gastric angle. Histological observation revealed hyperplastic change of foveolar epithelium with serrated glandular structure as well as a minute tubular adenocarcinoma component. Immunohistochemically, the lesion demonstrated gastrointestinal, predominantly gastric, phenotype (MUC5AC++, MUC6+, MUC2+, CD10-). Positive p53 immunoreactivity was detected in the carcinoma component of the lesion with a point mutation (G877T; R209I) of the gene and microsatellite instability of the BAT-RII locus; however, immunoreactivity of the mismatch repair gene product hMLH1 was well preserved in the cancer as well as in the hyperplastic lesion. The hyperplastic lesion with serrated glandular pattern would be a precancerous lesion of adenocarcinoma of the stomach.