Colorectal cancer pathophysiology

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To view the pathophysiology of familial adenomatous polyposis (FAP), click here
To view the pathophysiology of hereditary nonpolyposis colorectal cancer (HNPCC), click here

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Saarah T. Alkhairy, M.D., Roukoz A. Karam, M.D.[2], Elliot B. Tapper, M.D.

Overview

The pathogenesis of colorectal carcinoma (CRC) involves the molecular pathways for both sporadic and colitis-associated CRC. Sporadic instability originates from the epithelial cells that line the colon or rectum. Colitis-associated CRC includes genetic instability, epigenetic alteration, chronic inflammation, oxidative stress, and intestinal microbiota. Right-sided and left-sided tumors differ in their gross pathology depending on glandular architecture, cellular pleomorphism, and mucosecretion of the predominant pattern. Adenocarcinoma may present in three degrees of differentiation: well, moderately, and poorly differentiated.

Pathogenesis

The pathogenesis of colorectal carcinoma (CRC) involves the molecular pathways for both sporadic and colitis-associated CRC.

Sporadic colorectal cancers

The picture below depicts the molecular pathogenesis of sporadic colon cancer:[1] Sporadic colorectal cancer originates from the epithelial cells that line the colon or rectum; it may involve the following:[2]

  • Produces the APC protein, which prevents the accumulation of β-catenin protein (responsible for stem cell renewal)
  • Mutation of the APC protein leads to the accumulation of β-catenin protein and causes inappropriately high levels of stem cell renewal.
  • Produces the p53 protein, which monitors cell division and promotes apoptosis if there are cell defects
  • Mutations result in loss of control over cell division or apoptosis
  • TGF-β and DCC (Deleted in Colorectal Cancer)
  • Usually responsible for apoptosis, but deactivated in colorectal cancer
Molecular pathogenesis of sporadic colon cancer, (ɔ) Image courtesy of WikiDoc.org

Colitis-associated colorectal cancers

The picture below depicts the molecular pathogenesis of colitis-associated colon cancer:[1]

At a microbiological level, the development of colitis-associated colorectal cancers (CRC) can be linked to defects within the cell cycle.[3]

Although it is poorly understood, the following five factors may be responsible for its neoplastic changes:[1]

  • Intestinal microbiota[9]
    • The Modification of enteric flora by probiotic lactobacilli is a proposed mechanism that may contribute to the development of colitis-associated cancer.

Genetics

From a genetic standpoint, colorectal cancer can be divided into three categories:[10]

  • Sporadic (75% of cases)
    • No indication of a hereditary component
  • Familial (20% of cases)
  • Hereditary (10% of cases)
Appearance of the inside of the colon showing one invasive colorectal carcinoma (the crater-like, reddish, irregularly shaped tumor). - Source: librepathology.org

Gross Pathology

  • Right-sided tumors (ascending colon and cecum) tends to grow outwards from one location in the bowel wall (exophytic)
  • Left-sided tumours tend to be circumferential
Histopathologic image of colonic carcinoid stained by hematoxylin and eosin. - By No machine-readable author provided. KGH assumed (based on copyright claims). - No machine-readable source provided. Own work assumed (based on copyright claims)., CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=453828

Histology

  • Most tumors affecting the colon are carcinomas, and of these carcinomas almost 90% are adenocarcinomas.
  • Rarely, tumors of the colon are of other histologic types including hamartomas, neuroendocrine neoplasms, mesenchymal, or lymphomas.
  • The College of American Pathologists (CAP) and the American Joint Committee on Cancer/Union for International Cancer Control (AJCC/UICC) have both recommended the adoption of a two-tiered grading system for CRC and the use of gland formation as the only feature by which grade is assessed.[11]
  • Tumor cells form irregular tubular structures, harboring pleuristratification, multiple lumens, and reduced stroma
  • Sometimes, tumor cells are discohesive and secrete mucus, which invades the interstitium producing large pools of mucus/colloid (optically "empty" spaces)
  • If the mucus remains inside the tumor cell, it pushes the nucleus at the periphery (signet-ring cell)



Grades of Colorectal Cancer

The grade describes how closely the cancer looks like normal tissue when seen under a microscope. This is sometimes used to distinguish whether a patient should get adjuvant treatment with chemotherapy after surgery.

  • Grade 1 - Well differentiated
  • Grade 2 - Moderately differentiated
  • Grade 3 - Poorly differentiated
  • Grade 4 - Undifferentiated

Video

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References

  1. 1.0 1.1 1.2 Kim, Eun Ran (2014). "Colorectal cancer in inflammatory bowel disease: The risk, pathogenesis, prevention and diagnosis". World Journal of Gastroenterology. 20 (29): 9872. doi:10.3748/wjg.v20.i29.9872. ISSN 1007-9327.
  2. Markowitz SD, Bertagnolli MM (2009). "Molecular origins of cancer: Molecular basis of colorectal cancer". N Engl J Med. 361 (25): 2449–60. doi:10.1056/NEJMra0804588. PMC 2843693. PMID 20018966.
  3. Scully R (2010). "The spindle-assembly checkpoint, aneuploidy, and gastrointestinal cancer". The New England Journal of Medicine. 363 (27): 2665–6. doi:10.1056/NEJMe1008017. PMID 21190461. Retrieved 2011-12-12.
  4. Zivić R, Bjelaković G, Koraćević D (1975). "[Amino acid constitution of the urine in children with rheumatic fever]". Reumatizam. 22 (1): 21–5. PMID 1118685.
  5. Itzkowitz S (2003). "Colon carcinogenesis in inflammatory bowel disease: applying molecular genetics to clinical practice". J Clin Gastroenterol. 36 (5 Suppl): S70–4, discussion S94-6. PMID 12702969.
  6. Kraus S, Arber N (2009). "Inflammation and colorectal cancer". Curr Opin Pharmacol. 9 (4): 405–10. doi:10.1016/j.coph.2009.06.006. PMID 19589728.
  7. Elzagheid A, Emaetig F, Alkikhia L, Buhmeida A, Syrjänen K, El-Faitori O; et al. (2013). "High cyclooxygenase-2 expression is associated with advanced stages in colorectal cancer". Anticancer Res. 33 (8): 3137–43. PMID 23898071.
  8. Ullman TA, Itzkowitz SH (2011). "Intestinal inflammation and cancer". Gastroenterology. 140 (6): 1807–16. doi:10.1053/j.gastro.2011.01.057. PMID 21530747.
  9. O'Mahony L, Feeney M, O'Halloran S, Murphy L, Kiely B, Fitzgibbon J; et al. (2001). "Probiotic impact on microbial flora, inflammation and tumour development in IL-10 knockout mice". Aliment Pharmacol Ther. 15 (8): 1219–25. PMID 11472326.
  10. Schlussel AT, Gagliano RA, Seto-Donlon S, Eggerding F, Donlon T, Berenberg J; et al. (2014). "The evolution of colorectal cancer genetics-Part 1: from discovery to practice". J Gastrointest Oncol. 5 (5): 326–35. doi:10.3978/j.issn.2078-6891.2014.069. PMC 4173047. PMID 25276405.
  11. Compton CC, Fielding LP, Burgart LJ, Conley B, Cooper HS, Hamilton SR; et al. (2000). "Prognostic factors in colorectal cancer. College of American Pathologists Consensus Statement 1999". Arch Pathol Lab Med. 124 (7): 979–94. doi:10.1043/0003-9985(2000)124<0979:PFICC>2.0.CO;2. PMID 10888773.


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