Colorectal tumours

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Colorectal tumours are very common. They are the bread and butter of GI pathology. Non-tumour colon is dealt with in the colon article.

An introduction to gastrointestinal pathology is in the gastrointestinal pathology article. The precursor lesion of colorectal carcinoma (CRC) is, typical, an adenomatous polyp. Polyps are discussed in the intestinal polyps article.

Classification

Other tumours - many (incomplete list):[2]

  • Mucinous carcinoma.
  • Adenosquamous carcinoma.
  • Signet-ring carcinoma.
  • Squamous carcinoma.
  • Neuroendocrine neoplasms (carcinoid tumours).
  • Lipoma.
  • Leiomyoma.
  • Gastrointestinal stromal tumour (GIST) - dealt with in a separate article.
  • Angiosarcoma.
  • Lymphoma (Non-Hodgkin's lymphoma).

Grading

  • "Adenocarcinoma in situ" and "high-grade dysplasia" is used interchangeably by many in the colon and rectum.
    • Splitting hairs - adenocarcinoma in situ is invasion into the lamina propria, high-grade dysplasia does not have lamina propria invasion. Ergo, the difference (in my opinion) amounts to seeing a desmoplastic stroma (adenocarcinoma) or not seeing one (dysplasia).

Grading of tumours:

  • Tis - in situ (intramucosal).
  • T1 - into submucosa (through mucularis mucosae).
    • This is different than elsewhere, e.g. in the small bowel tumour cells in the lamina propria is defined as T1. The rationale for the T1 definition in CRC is that no lymphatics are present in the mucosa, ergo no risk of distant spread.
  • T2 - into muscularis propria.
  • T3 - into fat beyond musclaris propria.
  • T4 - into something else.

Nodes:

  • N0 - no positive nodes.
  • N1 - 1-3 positive nodes.
  • N2 - 4+ positive nodes.

Staging of colorectal cancer

Simple version

Tumour/node grade for stage:[3]

  • Stage I - T1 or T2 N0 M0.
  • Stage II - T3 or T4 N0 M0.
  • Stage III - Tx N1 or N2 M0.
  • Stage IV - Tx Nx M1.

Complex version

Detailed tumour/node grade for stage:[4]

  • Stage I - T1 or T2.
  • Stage IIA - T3.
  • Stage IIB - T4.
  • Stage IIIA - T1 N1 or T2 N1.
  • Stage IIIB - T3 N1 or T4 N1.
  • Stage IIIC - Tx N2.
  • Stage IV - Tx Nx M1.

Pathogenesis

Colorectal carcinoma is thought to arise from one of two pathways:[5][6]

  1. APC (adenomatous polyposis coli) gene mutation pathway, AKA classic adenoma-carcinoma pathway.
  2. Serrated pathway, AKA mutator pathway, mismatch repair pathway.
    • Associated with microsatellite instability (MSI).
    • Common associated gene mutations:[7]
      1. MLH1.
      2. MSH2.
      3. MSH6.

MSI cancers

General

Features:[8]

  • Prognosis: slightly better than other CRC without MSI.
  • Treatment implication: different response to chemotherapy.

MSI classification

MSI associated cancers can be classified into:[9][10]

  • MSI-H >= 30% of loci have abnormality.
  • MSI-L <30% of loci have abnormality.

Gross

Features:[8]

  • Location: left-sided predominance.

Microscopic

Features:[8]

  • Lymphocytic infiltrate.
  • Pushing border.[11]
  • Histomorphology:
    • Poorly differentiated mucinous
    • Signet ring.
    • Medullary.[12]

Syndromes

  • Lynch syndrome AKA hereditary non-polyposis colorectal cancer syndrome (HNPCC).
  • Familial polyposis coli (FPC).

See also

References

  1. ↑ Cotran, Ramzi S.; Kumar, Vinay; Fausto, Nelson; Nelso Fausto; Robbins, Stanley L.; Abbas, Abul K. (2005). Robbins and Cotran pathologic basis of disease (7th ed.). St. Louis, Mo: Elsevier Saunders. pp. 864. ISBN 0-7216-0187-1.
  2. ↑ Humphrey, Peter A; Dehner, Louis P; Pfeifer, John D (2008). The Washington Manual of Surgical Pathology (1st ed.). Lippincott Williams & Wilkins. pp. 198. ISBN 978-0781765275.
  3. ↑ TN 2006 GS27.
  4. ↑ http://www.cancer.org/docroot/CRI/content/CRI_2_4_3X_How_is_colon_and_rectum_cancer_staged.asp
  5. ↑ Goldstein NS (January 2006). "Serrated pathway and APC (conventional)-type colorectal polyps: molecular-morphologic correlations, genetic pathways, and implications for classification". Am. J. Clin. Pathol. 125 (1): 146–53. PMID 16483003.
  6. ↑ Rüschoff J, Aust D, Hartmann A (2007). "[Colorectal serrated adenoma: diagnostic criteria and clinical implications]" (in German). Verh Dtsch Ges Pathol 91: 119–25. PMID 18314605.
  7. ↑ URL: http://www.hpcgg.org/LMM/comment/HNPCC_info.jsp. Accessed on: 24 July 2010.
  8. ↑ 8.0 8.1 8.2 Boland CR, Goel A (June 2010). "Microsatellite instability in colorectal cancer". Gastroenterology 138 (6): 2073–2087.e3. doi:10.1053/j.gastro.2009.12.064. PMID 20420947.
  9. ↑ Lawes DA, Pearson T, Sengupta S, Boulos PB (August 2005). "The role of MLH1, MSH2 and MSH6 in the development of multiple colorectal cancers". Br. J. Cancer 93 (4): 472–7. doi:10.1038/sj.bjc.6602708. PMC 2361590. PMID 16106253. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2361590/.
  10. ↑ Guidoboni M, Gafà R, Viel A, et al. (July 2001). "Microsatellite instability and high content of activated cytotoxic lymphocytes identify colon cancer patients with a favorable prognosis". Am. J. Pathol. 159 (1): 297–304. PMC 1850401. PMID 11438476. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1850401/.
  11. ↑ AP. 18 October 2010.
  12. ↑ Truta B, Chen YY, Blanco AM, et al. (2008). "Tumor histology helps to identify Lynch syndrome among colorectal cancer patients". Fam. Cancer 7 (3): 267–74. doi:10.1007/s10689-008-9186-8. PMID 18283560.
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