Colon tumor
Carcinoma
General

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

Revised: 16 February 2016, last major update February 2016

Copyright: (c) 2002-2016, PathologyOutlines.com, Inc.

PubMed Search: Carcinoma [title] colon
Cite this page: General. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/colontumorcarcinomageneral.html. Accessed December 8th, 2016.
Definition / General
  • Primary epithelial malignancy arising in the colorectum
Essential Features
  • More than 1 million new cases worldwide per year
  • #2 or #3 most common cancer and cause of cancer deaths in men and in women
  • 98% of colonic cancers are adenocarcinomas
Epidemiology
  • Most common gastrointestinal tumor in USA; less common in Africa, Asia and parts of South America
  • Affects 5% of the US population during their lifetime
  • More common in men than women
  • Most common cause of cancer related death among nonsmokers
  • Peak age 60 - 79 years
    • < 20% of cases occur before age 50
    • Rare before age 40 except in patients with a predisposition syndrome
Sites
  • May arise anywhere in the colorectum, but sigmoid colon and rectum are most common sites
Etiology
  • Risk factors: older age, obesity, physical inactivity, alcohol consumption, inflammatory bowel disease, schistosomiasis, family history of colorectal neoplasia
  • Polyposis syndromes: familial adenomatous polyposis and variants (APC gene), Lynch syndrome and variants (MLH1, MSH2, MSH6 and PMS2 genes), juvenile polyposis (SMAD4, PTEN genes), Peutz-Jeghers syndrome (STK11 gene)
  • Dietary risk factors: low vegetable fiber, high refined carbohydrates, increased beef consumption, decreased vitamins A/C/E
    • Low fiber prolongs transit time (toxic oxidative byproducts are in longer contact with colonic mucosa) and alters bacterial flora
    • Beef consumption enhances synthesis of bile acids by liver, which may be converted into carcinogens by bile acids
Clinical Features
  • Screening: colonoscopy, guaiac fecal occult blood test
  • Symptoms:
    • Right sided carcinomas cause anemia (due to blood loss) and vague abdominal pain
    • Left sided carcinomas cause change in bowel habits (diarrhea or constipation) and rectal bleeding
    • Some patients may be asymptomatic, and tumors are detected by screening, especially if lesion is early
  • Metastases:
    • 60% of patients have lymph node or distant metastases at diagnosis
    • Most common metastatic sites are regional lymph nodes, liver, peritoneum, lung, ovaries
    • Metastases may simulate primary tumors of affected organs
  • Prognosis:
    • 5 year survival is 40 - 60%
    • Most recurrences are within 2 years
Laboratory
  • Serum CEA: elevated levels associated with various carcinomas or liver disease
    • Useful for monitoring recurrences but not sensitive for early tumors
Radiology Description
  • Imaging allows for clinical staging (depth of invasion, possibility of metastasis)
Prognostic Factors
  • Poor prognostic factors: high stage, positive margins (particularly radial margin in rectal carcinoma), poor differentiation, signet ring cells, flat or ulcerative gross configuration, tumor budding, tumor perforation, free tumor cells in peritoneal space (Am J Clin Pathol 2003;119:108), lymphovascular invasion, perineurial invasion
  • Lack of CDX2 expression (N Engl J Med 2016;374:211) and reduced claudin 1 expression (Mod Pathol 2005;18:511) portend worse survival in stage II tumors
  • HER2/neu and VEGF are not important prognostic markers (BMC Cancer 2011;11:277)
Treatment
  • Resection with endoscopic follow up
  • Local excision (endoscopic mucosal resection) for early rectal carcinoma
  • Surgical excision of isolated distant metastases
  • Radiation therapy or chemotherapy (including neoadjuvant if rectal)