Skip to content

Colorectal Cancer Health Center

Font Size

Rectal Cancer Treatment (PDQ®): Treatment - Health Professional Information [NCI] - Cellular Classification and Pathology of Rectal Cancer

The World Health Organization (WHO) classification of tumors of the colon and rectum include the following:[1]

Epithelial Tumors

Recommended Related to Colorectal Cancer

Who is at Risk?

For the great majority of people, the major factor that increases a person's risk for colorectal cancer (CRC) is increasing age. Risk increases dramatically after age 50 years; 90% of all CRCs are diagnosed after this age. The history of CRC in a first-degree relative, especially if before the age of 55 years, roughly doubles the risk. Other risk factors are weaker than age and family history. People with inflammatory bowel disease have a much higher risk of CRC. A small percentage (<5%) of CRCs...

Read the Who is at Risk? article > >


  • Tubular.
  • Villous.
  • Tubulovillous.
  • Serrated.

Intraepithelial neoplasia (dysplasia) associated with chronic inflammatory diseases

  • Low-grade glandular intraepithelial neoplasia.
  • High-grade glandular intraepithelial neoplasia.


  • Adenocarcinoma.
  • Mucinous adenocarcinoma.
  • Signet-ring cell carcinoma.
  • Small cell carcinoma.
  • Adenosquamous carcinoma.
  • Medullary carcinoma.
  • Undifferentiated carcinoma.

Carcinoid (well-differentiated neuroendocrine neoplasm)

  • Enterochromaffin (EC)-cell, serotonin-producing neoplasm.
  • L-cell, glucagon-like peptide and pancreatic polypeptide/peptide YY (PYY)-producing tumor.
  • Others.

Mixed carcinoma-adenocarcinoma

  • Others.

Nonepithelial Tumors

Malignant lymphomas

Adenocarcinomas account for the vast majority of rectal cancers. Other histologic types of colorectal cancer account for an estimated 2% to 5% of colorectal tumors.[2]


  1. Hamilton SR, Aaltonen LA: Pathology and Genetics of Tumours of the Digestive System. Lyon, France: International Agency for Research on Cancer, 2000.
  2. Kang H, O'Connell JB, Leonardi MJ, et al.: Rare tumors of the colon and rectum: a national review. Int J Colorectal Dis 22 (2): 183-9, 2007.

    This information is produced and provided by the National Cancer Institute (NCI). The information in this topic may have changed since it was written. For the most current information, contact the National Cancer Institute via the Internet web site at http:// cancer .gov or call 1-800-4-CANCER.

    WebMD Public Information from the National Cancer Institute

    Last Updated: May 28, 2015
    This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.
    Next Article:

    Today on WebMD

    Colorectal cancer cells
    The right diagnosis is the most important factor.
    man with a doctor
    Our health check will steer you in the right direction.
    sauteed cherry tomatoes
    Fight cancer one plate at a time.
    bladder cancer x-ray
    Do you know the warning signs?
    Colon vs Rectal Cancer
    New Colorectal Treatments
    can lack of sleep affect your immune system
    Cancer Facts Quiz
    Virtual Colonoscopy
    Picture of the Colon
    Vitamin D