Alpha-methylacyl-CoA racemase (AMACR) is a novel tumor biomarker expressed in a number of neoplasms, including colorectal and prostatic adenocarcinomas. However, AMACR expression has not been investigated in preneoplastic and neoplastic lesions of the stomach. Using immunohistochemistry we studied the expression of AMACR in normal gastric mucosa (n=32), intestinal metaplasia (n=26), adenomas (n=29) and adenocarcinomas (n=132) of the stomach from 135 patients. Synchronous adenocarcinomas arising in the background of adenomas were observed in 26 cases. AMACR immunoreactivity was not observed in all normal gastric mucosa. Tissue from intestinal metaplasia, adenomas, and adenocarcinomas was positive in 7.7% (2/26), 79.3% (23/29), and 62.9% (83/132) of cases, respectively. The difference in AMACR expression between adenomas or adenocarcinomas and non-neoplastic mucosa was statistically significant (p=0.0001). Moreover, intestinal-type carcinomas showed significantly higher expression of AMACR (69.8%) compared to diffuse-type carcinomas (47.2%) (p=0.02). Our results indicate that as well as being an additional diagnostic tool, altered AMACR expression in gastric adenomas and intestinal-type carcinomas suggests that AMACR may be involved early in the development of intestinal-type gastric carcinomas.