• Neoplastic colon polyp with at least low grade dysplasia
• Precursor to invasive adenocarcinoma

• Dysplastic nuclei (elongated and hyperchromatic pseudostratification)
• < 25% villous component

• The word “adenoma” should not be used on its own, to avoid confusion with sessile serrated adenoma and traditional serrated adenoma
• > 25% villous component indicates tubulovillous adenoma or villous adenoma

• K63.5: colon polyp
• D12.6: adenomatous polyp

• Incidence increases with age; commonly encountered in patients over 50
• Estimated that 25% of men and 15% of women undergoing colonoscopy are found to have at least one adenoma (N Engl J Med 2006;355:2551)
• Men more commonly affected than women (Gastrointest Endosc 2011;74:135)

• Found more commonly in the left colon and rectum compared with other polyps

• Has a well documented "adenoma to carcinoma” sequence that involves mutations in KRAS, TP53, APC and beta-catenin (Cell 1990;61:759)
• Activation of KRAS leads to downstream signaling that influences survival, anti-apoptosis and proliferation (J Gastroenterol Hepatol 2012;27:1423)
• Wnt pathway: activation of Wnt pathway leads to beta-catenin accumulation in the nucleus and subsequent transcription and cell proliferation
• Mutations include loss of function of APC or beta-catenin mutations that resist degradation by APC (J Gastroenterol Hepatol 2012;27:1423)

• Decreased risk of conventional colorectal adenomas is associated with increased dietary fiber intake (Lancet 2003;361:1491), fruit consumption in women (Cancer Res 2006;66:3942) and folate intake (J Nutr 2005;135:2468)

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• <1 cm: usually asymptomatic and detected by screening colonoscopy
• >1 cm: may bleed, lead to iron deficiency anemia, obstruction; increased risk of progressing to carcinoma
• Mostly left sided in spontaneous polyps and in familial adenomatous polyposis; right sided in Lynch syndrome (Gut 2002;50:382)

• Diagnosis is made by histologic confirmation

• Colonoscopy is diagnostic and potentially curative (via polypectomy)
• High grade dysplasia and large polyps may warrant endoscopic mucosal resection or partial colectomy

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Contributed by Laleh Montaser, M.D.


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Contributed by Andrew L.J. Dunn, M.D.


Contributed by Christopher Hartley, M.D.


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• Inflammatory polyp: nuclei can become elongated like a tubular adenoma but nuclei are typically vesicular with round borders
• Tubulovillous adenoma, villous adenoma: surface architecture has > 25% villous component

• J Clin Pathol 2018;71:7, Int J Oncol 2013;43:973, Cell 2009;137:623

Which of the following gene mutations is implicated in a majority of tubular adenomas?


1. ALK
2. BAP1
3. KRAS
4. MDM2

C. KRAS mutations are implicated in up to 60% of adenomas and adenocarcinomas. BAP1 mutations are present in a subset of melanocytic tumors and mesotheliomas. MDM2 is amplified in liposarcoma and some of its variants. ALK mutations can be seen in inflammatory myofibroblastic tumor, anaplastic large cell lymphoma and a subset of lung adenocarcinomas.

Reference: Colon tumor - Tubular adenoma

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