Cancerous tumours of the anus

A cancerous tumour of the anus can grow into nearby tissue and destroy it. The tumour can also spread (metastasize) to other parts of the body. Cancerous tumours are also called malignant tumours.

Squamous cell carcinoma

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

Squamous cell carcinoma may also start in the perianal skin near the anus or on the skin of the buttocks (bum or bottom) further away from the anus. Squamous cell carcinoma in these areas may be treated differently than cancer in the anal canal. It is usually treated like non-melanoma skin cancer that is found on other areas of the body.

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. Anal adenocarcinoma is usually treated like rectal cancer. Find out more about treatment of rectal 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 (called melanocytes) that make melanin, which gives skin, hair and eyes their colour. 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 it can also start in the anus. Find out more about gastrointestinal stromal tumours.

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 parts of 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.

Extramammary Paget disease may be found in the perianal skin where there are a lot of sweat glands. The most common symptom is itching and thick reddened skin. It is usually treated with surgery. If it has spread to other parts of the body, chemotherapy is also used.

Expert review and references

  • Ahmed S, Eng C, Messick CA. Squamous cell carcinoma of the anal canal. Yalcin S, Phillip PA (eds.). Textbook of Gastrointestinal Oncology. Springer Nature Switzerland; 2019: 10:171–180.
  • Czito BG, Ahmed S, Kalady MF, Eng C. Cancer of the anal region. DeVita VT Jr., Lawrence TS, Rosenberg SA, eds. DeVita, Hellman, and Rosenberg's Cancer: Principles & Practice of Oncology. 11th ed. Philadelphia, PA: Wolters Kluwer; 2019: 64:997–1013.
  • Stewart DB, Gaertner WB, Glasgow SC, Herzig DO, Feingold D, Steele SR. Clinical practice guidelines for anal squamous cell cancers (revised 2018). Diseases of the Colon and Rectum. 2018: 61(7):775–774.

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