Gastrointestinal polyps — classification and differential diagnosis
Author: Faruk Skenderi, MD, PhDReviewed by: Semir Vranić, MD, PhDLast reviewed:
- WHO Classification of Tumours Editorial Board. Digestive System Tumours. 5th ed. IARC; 2019.
- Crockett SD, Nagtegaal ID. Terminology, molecular features, epidemiology, and management of serrated colorectal neoplasia. Gastroenterology. 2019;157(4):949-966. https://doi.org/10.1053/j.gastro.2019.06.041 (opens in new tab)
- Rex DK, et al. Serrated lesions of the colorectum: review and recommendations from an expert panel. Am J Gastroenterol. 2012;107(9):1315-1329. https://doi.org/10.1038/ajg.2012.161 (opens in new tab)
- Gupta S, et al. Recommendations for follow-up after colonoscopy and polypectomy: a consensus update by the US Multi-Society Task Force on Colorectal Cancer. Gastroenterology. 2020;158(4):1131-1153. https://doi.org/10.1053/j.gastro.2019.10.026 (opens in new tab)
A practical guide to the common colorectal and upper GI polyp types: adenomatous, hyperplastic, serrated, hamartomatous, and inflammatory pseudopolyps, with key histologic distinctions and malignant potential.
- Adenomatous polyp (tubular, tubulovillous, villous): dysplastic epithelium with elongated, hyperchromatic, pseudostratified nuclei and decreased mucin; report grade of dysplasia (low vs high) and completeness of excision.
- Hyperplastic polyp: elongated, serrated crypts restricted to the upper (luminal) portion, no cytologic dysplasia, low malignant potential; most common and usually left-sided/rectosigmoid.
- Sessile serrated lesion (SSL): horizontal growth along the muscularis mucosae, boot-shaped/dilated crypts at the base, serrations extending to the crypt base; dysplasia (if present) should be reported.
- Traditional serrated adenoma (TSA): ectopic crypt formation, tall columnar cells with eosinophilic cytoplasm, elongated pencillate nuclei, shows serrated or conventional low-grade dysplasia; high-grade dysplasia may develop — distinct biology from SSL.
- Hamartomatous polyps: juvenile polyps, Peutz-Jeghers hamartomas; distinguish by stroma, smooth-muscle arborisation, and associated syndromic risk.
- Inflammatory pseudopolyps: regenerating mucosa in a background of active inflammation (IBD); not true neoplasms, but dysplasia may arise in surrounding mucosa.
- Key immunohistochemistry: loss of MLH1/PMS2 in some SSLs with dysplasia; β-catenin nuclear accumulation in conventional adenomas; p53 aberrant expression in high-grade dysplasia.
- Clinical relevance: size ≥1 cm, villous architecture, high-grade dysplasia, and number of polyps increase CRC risk; correlate with endoscopic findings and familial/syndromic history.