Gastric Dysplasia: Diagnosis and Significance:

Genetic alterations in gastric adenomas of intestinal and foveolar phenotypes

Gastric adenomas are unusual neoplasms that can constitute one of the direct precursors to gastric adenocarcinoma. Most gastric adenomas are comprised of polypoid projections of dysplastic epithelium with at least focal intestinal-type differentiation (containing goblet cells and/or Paneth cells), whereas adenomas comprised entirely of dysplastic foveolar-type epithelium are rare. It has been shown that nearly all intestinal-type adenomas arise in association with background intestinal metaplasia and gastric atrophy, approximately 40% harbor high-grade dysplasia, and nearly one fourth progress to adenocarcinoma. In contrast, foveolar-type adenomas tend to occur in otherwise normal, nonatrophic gastric mucosa and rarely harbor high-grade dysplasia or carcinoma. Potential differences in the genetic alterations between intestinal-type and foveolar-type gastric adenomas have not been systematically studied. We investigated 11 intestinal-type and 7 foveolar-type gastric adenomas (all from patients without familial adenomatous polyposis) for alterations in APC (using 5q allelic loss assays and direct DNA sequencing of the mutation cluster region), beta-catenin (using direct DNA sequencing of the phosphorylation region in exon 3), K-ras (using direct DNA sequencing of codons 12 and 13), and microsatellite instability (MSI; using fluorescent-based PCR amplification of a standard panel of 5 microsatellite markers). Overall, 10 of 11 (91%) intestinal-type adenomas harbored at least one detectable genetic alteration, whereas only 3 of 7 (43%) of foveolar-type adenomas did (P =.047). However, no statistically significant differences in any particular genetic alteration were found. Among intestinal-type adenomas, APC alterations were present in seven (64%), high-level MSI in three (27%), and K-ras mutations in two (18%). Among foveolar-type adenomas, APC alterations were present in three (43%) and a K-ras mutation in one of six amplifiable polyps (17%). Neither APC nor MSI correlated with the size of the adenoma, but K-ras mutations were found only in lesions of > or = 1 cm. beta-catenin mutations were not present in any gastric adenoma, irrespective of the presence or absence of APC alterations. These results suggest that the types and frequencies of genetic alterations occurring in gastric and colorectal adenomas are similar. Although intestinal-type and foveolar-type gastric adenomas display divergent biologic behavior, the specific genetic events accounting for these differences in morphology and biologic behavior are unclear.

Gastric adenomas: intestinal-type and gastric-type adenomas differ in the risk of adenocarcinoma and presence of background mucosal pathology

Gastric adenomas are neoplastic growths characterized by localized, polypoid proliferations of dysplastic epithelium. They frequently arise in stomachs with a background of mucosal atrophy and intestinal metaplasia, and a higher risk of adenocarcinoma elsewhere in the stomach has been reported in patients with gastric adenomas. Additionally, some gastric adenomas themselves demonstrate neoplastic progression to infiltrating adenocarcinoma. However, previous studies have not comprehensively evaluated the background gastric mucosa and risk of adenocarcinoma, particularly in relation to the histologic classification of adenomas as either intestinal-type or gastric-type. We studied 61 gastric adenomas from 51 patients between 1985 and 2001. The adenomas were classified as intestinal-type (containing at least focal goblet cells and/or Paneth cells), gastric-type (lined entirely by gastric mucin cells on PAS/alcian blue stain), or indeterminate. We evaluated the histologic features of both the adenomas (location, multiplicity, degree of dysplasia, presence of adenocarcinoma within the polyp) and the surrounding gastric mucosa (presence of gastritis, intestinal metaplasia, and adenocarcinoma). Gastric adenomas were distributed equally throughout the stomach, were most frequently solitary (82%), and contained adenocarcinoma in nine cases (14.8%). There were 34 intestinal-type adenomas (56%) in 31 patients, 25 gastric-type adenomas (41%) in 18 patients (including 10 patients with familial adenomatous polyposis), and 2 of indeterminate type (3%). Intestinal-type adenomas were significantly more likely than gastric-type adenomas to show high-grade dysplasia (p <0.0001), adenocarcinoma within the polyp (p = 0.016), intestinal metaplasia in the surrounding stomach (p <0.000001), and gastritis (p = 0.002). Patients with intestinal-type adenomas were also more likely to have separate adenocarcinomas (five cases vs 0 cases), although this did not reach statistical significance. Gastric adenomas are rarely truly "sporadic" lesions. In any individual patient complete removal of the adenoma should be performed, and thorough biopsy of the surrounding gastric mucosa is essential to understand the clinicopathologic context of the adenoma.