Colon tumor
Polyps
Adenoma-general of colon

Author: Shilpa Jain, M.D.(see Authors page)

Revised: 7 December 2012, last major update September 2010

Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

PubMed Search: adenoma [title] general colon
Cite this page: Adenoma-general of colon. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/colontumoradenoma.html. Accessed December 9th, 2016.
Definition / General
  • Well established premalignant lesion, usually with polypoid areas of epithelial dysplasia
  • "Adenoma" is an incorrect term - they are not benign neoplasms
Epidemiology
  • In U.S., present in colon in 20% at age 40 years, 50% at age 60 years
  • In U.S. autopsy studies, almost all have tubular adenomas, < 5% have tubulovillous or villous adenomas
  • Low incidence in developing countries
  • No gender predilection
  • Decreased risk of adenoma is associated with dietary fiber intake (Lancet 2003;361:1491), fruit consumption in women (Cancer Res 2006;66:3942), folate intake (J Nutr 2005;135:2468)
  • Only weak association between fiber and adenoma recurrence (Am J Gastroenterol 2005;100:2789)
Clinical Features
  • Slow growing
  • 30% develop new polyps after mean 26 month follow up; higher risk if 3 or more adenomas and at least one in proximal colon (Dis Colon Rectum 2004;47:323)
  • Risk of invasive colorectal adenocarcinoma in the adenoma depends on size: < 1% if < 1 cm vs. 10% if > 2 cm; higher risk if villous component
  • Risk of subsequent carcinoma is related to 3 or more polyps, polyp location at transverse colon or proximal or [one study] presence of monotonous population of elongated cells (Am J Surg Pathol 2006;30:1120)
  • "Advanced adenomas" receive more aggressive clinical management (i.e. repeat colonscopy in 3 years instead of 5 years) and includes:
    • > 3 adenomas
    • Any adenoma > 1 cm with villous architexture
    • Any adenoma with high grade dysplasia
Treatment
  • Excision of a pedunculated adenoma, even with invasive carcinoma, is considered adequate treatment if margin is negative, there is no vascular or lymphatic invasion and carcinoma is moderate or well differentiated
  • Invasive adenocarcinoma in a sessile polyp requires more than polypectomy
Gross Description
  • Classified as pedunculated (with stalk), sessile or flat
  • Tubular are red (darker than surrounding mucosa)
  • Villous are shaggy with papillary fronds
  • True margin of resection should be inked when grossing or can be determined by diathermy artifact
Gross Images

Images hosted on other servers:

Polypoid tumor with gyrated surface sitting on a short stalk

Polypoid tumor

Micro Description
  • Either conventional (tubular, tubulovillous [5%] or villous [1%]), serrated or flat adenomas
  • Villous: At least > 75% villous component
  • Tubulovillous: 25 - 75% of villous component
  • Tubular: < 25% of villous component
  • The degree of villous differentiation increases with size of the adenoma
  • All subtypes contain epithelial proliferative dysplasia
  • Dysplasia can be classified as low grade or high grade, although some GI pathologists recommend not using high grade dysplasia terminology unless clinicians want to know
    • Low grade: pseudostratification or stratification of nuclei that reach only luminal half of the cell, but don’t reach cell surface; apical mucin is present; nuclei are elongated and dysplastic; mitotic activity, atypical mitosis and loss of polarity are minimal
    • High grade: Cytological and architectural changes of dysplasia; nuclei are enlarged, hyperchromatic or vesicular with prominent nucleoli; nuclei are stratified and reach luminal border; architectural changes include back to back glands, cribriform glands or irregular budding / branching of crypts; mitotic figures are prominent; reduced mucin; necrosis may be present
      • Note: high grade dysplasia present in 12% of adenomas
      • By definition, no invasion through muscularis mucosa into submucosa
      • Intramucosal carcinoma: invasion of mucosa or muscularis mucosa (but not beyond) with desmoplastic response; no biologic potential for metastases
Additional References