Introduction: Hyperplastic polyps (HPs) are benign epithelial lesions that are usually seen in 6th or 7th decades of life. In asymptomatic individuals older than 50 years undergoing colonoscopy, HPs are seen in about 10% of cases. The prevalence rate of HPs from autopsy studies is 20% to 35%. The underlying pathogenesis is inhibition of apoptosis which prevents shedding of mature surface epithelial cells leading to formation of polypoid structures.
Clinical Significance: True hyperplastic polyps have no malignant potential but must be separated from similar looking sessile serrated adenomas which do carry risk of malignant transformation. In addition, HPs may coexist with neoplastic polyps in the same colon.
Gross Morphology: Hyperplastic polyps can be seen anywhere in the colon but are more frequent in the distal colon and rectum than proximal colon. A typical hyperplastic polyp is sessile and usually smaller than 0.5 cm in size. On endoscopy, they appear as smooth nodular mucosal protrusions, often multiple and usually located on the crest of the mucosal folds. They may be indistinguishable from adenomatous polyps.
Microscopic Appearance: The surface of hyperplastic polyps shows irregular tufting or micropapillary configuration (as seen in this image). When sectioned longitudinally, the elongated crypts with their intraluminal folds create a serrated (or sawtooth) appearance. The lining cells are mature goblet cells and absorptive cells which have a basally located nucleus and abundant mucinous cytoplasm. There is no cytologic atypia. Mitotic activity is limited to the base of the crypts.
Treatment: HPs are small, have no malignant potential and rarely cause symptoms. However, since they cannot reliably be distinguished from adenomatous polyps or sessile serrated adenomas during endoscopy, they are usually removed.
Image courtesy of: @Patholwalker