Gastric Adenomas (Raised Intraepithelial Neoplasia)
The most common gastric neoplastic polyp is an epithelial dysplastic growth still commonly referred to as an adenoma, despite the new nomenclature (raised intraepithelial neoplasia) suggested by the World Health Organization.[44,45] In the Western industrialized world, H pylori–related sporadic gastric adenomas have become rare, accounting for less than 1% of all gastric polyps. This contrasts markedly with some East Asian regions, where the incidence of gastric cancer remains high and gastric adenomas still constitute approximately a quarter of all gastric polyps.[46,47] Similar to hyperplastic polyps, gastric adenomas occur with similar frequency in men and women, most commonly in the sixth and seventh decades. Endoscopically, they have a velvety lobulated appearance and are usually solitary (Figure 4). Although they can be found anywhere in the stomach, they are located more often in the antrum. The narrow band imaging features of gastric adenomas are not yet well defined.
Adenoma. (A) Flat gastric adenoma with a velvety appearance in the distal body of the stomach. (B) Gastric adenomas consist of dysplastic columnar epithelium indistinguishable from colonic adenoma. In resected specimens, the only clue to their gastric origin is often a small remnant of gastric tissue from which they originate (arrow).
Gastric adenomas consist of dysplastic epithelial cells that often arise in a background of atrophy and intestinal metaplasia typically associated with H pylori infection. As in the colon, gastric adenomas can be viewed as part of a sequence leading from dysplasia to carcinoma. The larger an adenomatous polyp, the greater the probability it contains foci of adenocarcinoma. Synchronous adenocarcinomas, in other areas of the stomach, have been reported in up to 30% of patients with adenomas containing foci of adenocarcinoma.[48,49,50]
Gastric adenomas frequently arise in a background of chronic atrophic gastritis. Because this is a precursor lesion for gastric adenocarcinoma, in addition to completely excising all adenomas, the severity and extent of the atrophic gastritis should be evaluated. The same biopsy protocols[39,40] and the use of the OLGA or Operative Link on Gastritis/Intestinal Metaplasia Assessment system suggested in the section "Hyperplastic Polyps" should be followed.[37,38] It must be emphasized that adenomas are neoplastic lesions (ie, past the stage of preneoplastic) and, therefore, all patients with a diagnosis of gastric adenoma need to be placed in a surveillance program irrespective of their atrophy stage. Eradication of H pylori followed by confirmation of the cure by biopsy examination or urea breath test is necessary in these patients.
Histopathologic Diagnostic Tips: Special Stains, Immunohistochemistry, and Molecular Studies
Gastric adenomas are neoplastic lesions with malignant potential. Therefore, multiple sections from each lesion must be examined to exclude invasion. Outside the research arena, neither special stains nor molecular studies are necessary.
Clin Gastroenterol Hepatol. 2013;11(11):1374-1384. © 2013 AGA Institute