Colorectal tumours

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

Colonic tumours and rectal tumours redirect here.

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

Classification

Most common

Others

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

Notes:

Squamous carcinoma

  • Rare.
    • In the context of a rectal tumour, retrograde growth from the anus should be considered.

Staging of colorectal cancer

Pathogenesis of colorectal carcinoma

Overview

Colorectal carcinoma is thought to arise from one of two pathways:[4][5]

  1. APC (adenomatous polyposis coli) gene mutation pathway, AKA classic adenoma-carcinoma pathway.
  2. Serrated pathway, AKA mutator pathway, mismatch repair pathway.

Syndromes

Both of the above described pathways are associated with syndromes:

  1. Familial adenomatous polyposis (FAP) or familial polyposis coli (FPC).
  2. Lynch syndrome (AKA hereditary non-polyposis colorectal cancer syndrome (HNPCC)).

Pathways

APC gene mutation pathway

Microscopic:

Mismatch repair pathway

Other ancillary studies

BRAF V600E mutation

Features:[6]

  • Independently associated with BRAF V600E:
    • Usually older (>70 years old).
    • Female gender.
    • Right-sided tumour location.
  • Worse prognosis - in the context of metastatic disease.

KRAS mutation

Features:[7][8]

  • Patient must have wild type KRAS to get drugs; KRAS mutation predicts resistance to cetuximab (Erbitux) and panitumumab (Vectibix).

Microsatellite instability cancers

  • Abbreviated MSI cancers.

Specific entities

Colorectal adenocarcinoma

  • AKA colorectal adenocarcinoma not otherwise specified.
  • AKA colorectal carcinoma, abbreviated CRC.

Secondary colorectal cancer

General

  • Uncommon.
  • May be suspected.

Microscopic

Features:

  • Normal colorectal mucosa.
  • Atypical cells in the lamina propria or submucosa.

DDx:

  • Colorectal neuroendocrine tumour.

Images

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. Tozawa E, Ajioka Y, Watanabe H, et al. (2007). "Mucin expression, p53 overexpression, and peritumoral lymphocytic infiltration of advanced colorectal carcinoma with mucus component: is mucinous carcinoma a distinct histological entity?". Pathol. Res. Pract. 203 (8): 567–74. doi:10.1016/j.prp.2007.04.013. PMID 17679024.
  4. 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.
  5. 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.
  6. 6.0 6.1 Tie J, Gibbs P, Lipton L, et al. (July 2010). "Optimizing targeted therapeutic development: Analysis of a colorectal cancer patient population with the BRAF(V600E) mutation". Int J Cancer. doi:10.1002/ijc.25555. PMID 20635392.
  7. Dunn EF, Iida M, Myers RA, et al. (October 2010). "Dasatinib sensitizes KRAS mutant colorectal tumors to cetuximab". Oncogene. doi:10.1038/onc.2010.430. PMID 20956938.
  8. Di Nicolantonio F, Martini M, Molinari F, et al. (December 2008). "Wild-type BRAF is required for response to panitumumab or cetuximab in metastatic colorectal cancer". J. Clin. Oncol. 26 (35): 5705–12. doi:10.1200/JCO.2008.18.0786. PMID 19001320.