Extra-Ampullary Duodenal Polyps: Reappraisal Based on Current Morphological and Immunohistochemical Features, A More Accurate and Clinically Significant Classification

Summary: Duodenal epithelial polyps (DEPs) have been reported in approximately 1.5% - 3.0% of individuals referred for upper endoscopy. Recent advances in endoscopic techniques have increased the detection rate of these polyps and have allowed removal of lesions up to 2 cm in diameter. DEPs can occur as sporadic polyps, usually identified incidentally during upper endoscopy commonly performed for other reasons, or in the setting of familial polyposis, in which they are usually multiple and sometimes carpeting the entire duodenal surface. They may present as sessile or pedunculated polyps, nodules, excrescences, or subtle abnormalities of the mucosa located either in the duodenal bulb, ampullary/periampullary region, or in the distal portion of the duodenum. Most are benign and usually associated with peptic injury, duodenitis or inflammatory lesions; however, a small group are neoplastic with the potential progression to adenocarcinoma. Histologically they are broadly classified as non-neoplastic epithelial polyps and neoplastic epithelial polyps; some of which, like the ectopic gastric mucosa and the polyps related to Brunner’s gland hyperplasia, are identified frequently and others, like duodenal adenoma with gastric phenotype and serrated adenoma with traditional serrated adenoma (TSA)-like features, less frequently or rarely. In this article, we will review the salient clinicopathologic features and treatment options of DEPs, and provide an update on their classification and risk stratification based on the morphology, immunophenotype, molecular features and clinical outcome.