Gastric Adenomas and Mimickers: A Review

Gastric adenomas are epithelial premalignant neoplasms which may appear similar on endoscopic examination; however, histologically, they are classified into four distinct subtypes according to the World Health Organization (WHO) Classification of Tumors of the Digestive System: intestinal adenoma, foveolar-type adenoma, oxyntic gland adenoma, and pyloric gland adenoma. Each subtype has characteristic histologic features that are essential for accurate diagnosis, although distinction can be challenging due to overlapping morphologic patterns. Moreover, these entities differ in their potential for malignant transformation and in their associations with hereditary or syndromic conditions. The objective of this review is to provide a practical guide for the histopathologic diagnosis of gastric adenomas, summarize the evidence regarding their risk of associated malignancy or malignant transformation, and review current recommendations for clinical follow-up and management. Given that various lesions may present endoscopically as gastric polyps, this manuscript also reviews both epithelial and non-epithelial mimickers of gastric adenomas.