Gastric Hyperplastic Polyps: A Heterogeneous Clinicopathologic Group Including a Distinct Subset Best Categorized as Mucosal Prolapse Polyp

Gastric hyperplastic polyps are the second most common subtype of gastric polyps. There has been an ongoing debate about their precise diagnostic criteria and etiological associations. A total of 208 gastric polyps that were originally diagnosed as hyperplastic polyps in our department during an 8-year period were reviewed using recently emphasized diagnostic criteria, and their clinicopathologic associations were explored. Only 41 cases were confirmed as hyperplastic polyps, whereas 103 cases (49%) were reclassified as polypoid foveolar hyperplasia, and 64 cases (31%) were diagnosed as gastric mucosal prolapse polyps. Gastric mucosal prolapse polyps were distinguished by basal glandular elements, hypertrophic muscle fibers ascending perpendicularly from the muscularis mucosae, and by thick-walled blood vessels. This hitherto undescribed polyp is more commonly sessile than hyperplastic polyps (P=0.0452) and is found more often in the antropyloric region (P: 0.0053). Only 20.6% of hyperplastic polyps were associated with Helicobacter pylori infection. Our findings highlight that gastric polypoid lesions that have morphologic similarities may be related to various mechanisms, including inflammatory and prolapse processes. The predominantly antral location of gastric mucosal prolapse polyps, a zone of pronounced peristalsis, suggests that mucosal prolapse plays a role in the development of these common polyps. Evaluation of the prevalence and clinical associations of these distinctive polyps awaits further studies.