Intramucosal carcinoma

Topic Completed: 3 March 2021

Minor changes: 8 March 2021

Copyright: 2002-2021,, Inc.

PubMed Search: "Intramucosal carcinoma" colon

Raul S. Gonzalez, M.D.
Page views in 2020: 7,637
Page views in 2021 to date: 9,257
Cite this page: Gonzalez RS. Intramucosal carcinoma. website. Accessed October 16th, 2021.
Definition / general
  • Malignant change confined to mucosa (considered pTis in AJCC staging)
  • Proper cutoff between high grade dysplasia and intramucosal carcinoma is not entirely clear
Essential features
  • Adenocarcinoma solely within the mucosal layer of the colon
  • Usually within a polyp but may occur in flat mucosa in inflammatory bowel disease
  • Term typically not used by Western pathologists, who prefer high grade dysplasia
  • Controversial term that reflects differing thresholds for malignancy between the West (higher threshold) and Japan (lower threshold), as Japanese pathologists often diagnose as malignant what Western pathologists might call high grade dysplasia
  • United States Preventive Services Task Force specifically recommends against using the term intramucosal carcinoma for lesions confined to the mucosa (Gastrointest Endosc 2020;92:997)
Clinical features
Case reports
Clinical images

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Mass in colonoscopy

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Subpeduculated polyp

Gross description
  • May appear as a flat / ulcerated lesion or arise in a polyp
Gross images

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Resected intramucosal carcinoma

Microscopic (histologic) description
  • Glandular proliferation showing high grade nuclei and architectural complexity, extending no deeper than the muscularis mucosae
  • Necrosis, desmoplasia and single malignant cells may suggest intramucosal carcinoma over high grade dysplasia but this remains subjective
  • Often arises in an adenoma but may occur in flat colonic mucosa (such as in patients with inflammatory bowel disease)
  • May rarely show signet ring cells (Virchows Arch 2009;454:115)
Microscopic (histologic) images

Contributed by Raul S. Gonzalez, M.D.
Intramucosal carcinoma Intramucosal carcinoma

Intramucosal carcinoma

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Intramucosal adenocarcinoma

Sample pathology report
  • Rectum, mass, biopsy:
    • Tubulovillous adenoma with extensive high grade dysplasia (see comment)
    • Comment: The findings are compatible with an interpretation as intramucosal carcinoma, though this concept is rarely applied to colorectal lesions. The sample is relatively superficial and an unsampled invasive process cannot be excluded.
Differential diagnosis
Board review style question #1
Which of the following is true about intramucosal carcinoma of the colorectum?

  1. It only arises within traditional serrated adenomas
  2. Roughly 10% of cases metastasize to lymph nodes despite early stage
  3. There are well defined histologic criteria to distinguish it from high grade dysplasia
  4. Usage of the term differs between Eastern and Western pathologists
Board review style answer #1
D. Usage of the term differs between Eastern and Western pathologists

Comment Here

Reference: Intramucosal carcinoma
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