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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

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  • 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.
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