['To investigate the relation of fatty acid synthase (FAS) expression to the clinicopathological characteristics of gastric cancers and gastric tumorigenesis.', 'FAS expression was examined immunohistochemically in 626 gastric cancers, 51 gastric adenomas, and non-neoplastic epithelium contiguous with cancer tissue including normal foveolae, intestinal metaplasia, regenerative epithelium, and gastric glands. FAS expression was found in more than 70% of gastric cancers. Interestingly, it occurred preferentially in differentiated carcinomas, male cases, and in patients over 51 years old. Although previous reports showed that FAS expression is closely related to cancer progression, in gastric cancers FAS expression had no relationship with prognosis, cancer progression as indicated by depth of invasion, venous and lymphatic permeation, and distant metastasis. Gastric tubular adenoma and intestinal metaplasia, which are thought to be associated with well-differentiated gastric carcinomas, showed a frequency of FAS expression similar to that of differentiated carcinomas; however, normal foveolae and gastric glands showed no or less FAS expression.'] Is fatty acid synthase highly expressed in carcinoma , adenoma and in regenerative epithelium and intestinal metaplasia of the stomach?