Cancerous tumours of the anus

A cancerous tumour of the anus can invade, or grow into, and destroy nearby tissue. It can also spread, or metastasize, to other parts of the body. Cancerous tumours are also called malignant tumours.

Squamous cell carcinoma

Most anal cancers are squamous cell carcinomas. This type of cancer starts in squamous cells that line the anal canal and make up the surface of the perianal skin.

Squamous cell carcinoma of the perianal skin may be treated differently than cancer in the anal canal. It is usually treated like skin cancer in other areas of the body (called non-melanoma skin cancer) when in an early stage.

Rare anal tumours

The following cancerous tumours of the anus are rare.

Adenocarcinoma starts in gland cells in the anal canal or perianal skin. It usually starts in the upper part of the anal canal, near the rectum. When adenocarcinoma starts in sweat glands, it is called Paget disease. Paget disease can start in sweat glands anywhere in the body, but it develops most often in the perianal skin or the skin on the breast. An adenocarcinoma of the anus is usually treated like rectal cancer. Find out more about colorectal cancer.

Basal cell carcinoma is a type of non-melanoma skin cancer that can develop in the perianal skin. It is usually treated with surgery or radiation therapy. Find out more about non-melanoma skin cancer.

Melanoma is a type of skin cancer that starts in cells that make melanin, which gives skin, hair and eyes their colour (called melanocytes). It can start in the anal canal and is often treated with surgery. Find out more about melanoma.

Gastrointestinal stromal tumour (GIST) is a type of soft tissue sarcoma. It can start anywhere along the digestive tract. GIST is most common in the stomach and small intestine, but can also start in the anus. Find out more about gastrointestinal stromal tumours (GISTs).

Kaposi sarcoma is a type of tumour that develops in the blood and lymph vessels. It usually develops on or under the skin, including perianal skin. It can also develop in membranes that line the anal canal. Find out more about Kaposi sarcoma.

Neuroendocrine cancer is a type of tumour that can develop in the digestive system, including the anus. When it develops in the anus, it often starts in the anal canal near the rectum. Find out more about neuroendocrine cancer.

Expert review and references

  • American Society of Clinical Oncology. Anal Cancer. 2014:
  • American Society of Clinical Oncology (ASCO). Sarcoma, Kaposi. 2011:
  • Czito BG, Ahmed S, Kalady M, Eng C . Cancer of the Anal Region. DeVita VT Jr, Lawrence TS, Rosenberg SA. Cancer: Principles and Practice of Oncology. 10th ed. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins; 2015: 61:842-856.
  • Penn Medicine . Anal Cancer: The Basics . University of Pennsylvania ; 2015 :
  • Reidy-Lagunes D, Goodman K, Saltz LB . Unusual tumors of the colon, rectum, and anus. Raghavan D, Blanke CD, Honson DH et al (eds.). Textbook of Uncommon Cancer. 4th ed. Wiley Blackwell; 2012: 32:453-463.
  • von Mehren M, Flieder DB, Raut CP . Gastrointestinal stromal tumors. Raghavan D, Blanke CD, Honson DH et al (eds.). Textbook of Uncommon Cancer. 4th ed. Wiley Blackwell; 2012: 33:465-483.