Colon tumor
Small early flat carcinoma of colon

Author: Raul Gonzalez M.D. (see Authors page)

Revised: 4 September 2015, last major update August 2015

Copyright: (c) 2002-2015,, Inc.

PubMed Search: Small early flat carcinoma
Definition / General
  • Term used primarily in Japan for low-stage colorectal carcinomas with flat configuration
  • Not widely diagnosed in the USA; not officially recognized by the WHO
  • Epidemiology
  • Represents 6-10% of colonic cancers diagnosed in Japan
  • Does occur in Western countries (Gut 2002;51:550)
  • Sites
  • Usually develops in the right colon, in older patients (Dis Colon Rectum 2005;48:101)
  • Pathophysiology
  • May develop from flat adenomas, which are more likely to harbor malignancy than polypoid ones (JAMA 2008;299:1027)
  • May be an important precursor of advanced malignancies (Ann Acad Med Singapore 2003;32:263)
  • Tend to invade submucosa at a smaller size than polypoid lesions (Ann Pathol 2002;22:18)
  • Etiology
  • p53 dependent apoptosis may play a role in development (Dis Colon Rectum 2000;43:S23)
  • Clinical Features
  • May act aggressively despite small size
  • Diagnosis
  • Flat lesions may be easier to detect using chromoscopy (spraying dye on mucosa during colonoscopy) (Int J Clin Oncol 2006;11:1)
  • Prognostic Factors
  • Tumors with central depression tend to rapidly invade submucosa (World J Surg 2000;24:1075)
  • Case Reports
  • 52 year old man with primary minute invasive de novo colonic adenocarcinoma appearing as submucosal tumor (Int J Gastrointest Cancer 2005;36:177)
  • 81 year old woman with early colonic carcinoma with extensive lymph node metastases (Int J Colorectal Dis 2001;16:262)
  • Treatment
  • May be curable using endoscopic mucosal resection
  • Clinical Images
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    Depressed lesion in colon

    Gross Description
  • Flat, plaque-like lesion, often with central depression
  • Malignancy typically measures 1 cm or less
  • Gross Images
    Missing Image

    Slightly concaved surface

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    Prominent concave surface

    Micro Description
  • Adenocarcinoma limited to mucosa or submucosa, by definition
  • Height is usually less than twice the height of adjacent normal mucosa
  • Architectural changes mild; cytologic features resemble high-grade dysplasia
  • Micro Images
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    Invasion of submucosa

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    Minute focus of submucosal invasion (arrow)

    Molecular / Cytogenetics Description
  • Loss of heterozygosity of 17p, 18p, 18q, and 22q, coupled with LOH of other loci (Ann Oncol 2006;17:43)