About anal cancer

What is anal cancer?

Anal cancer is a disease in which malignant (cancer) cells form in the tissues of the anus.

The anus is the end of the large intestine, below the rectum, through which stool (solid waste) leaves the body. The anus is formed partly from the outer skin layers of the body and partly from the intestine. Two ring-like muscles, called sphincter muscles, open and close the anal opening and let stool pass out of the body. The anal canal, the part of the anus between the rectum and the anal opening, is about 1-1 ½ inches long.

Anatomy of the lower digestive system, showing the colon and other organs.

The skin around the outside of the anus is called the perianal area. Tumors in this area are skin tumors, not anal cancer.

Being infected with the human papillomavirus (HPV) increases the risk of developing anal cancer.



What are the symptoms for anal cancer?

Anal cancer signs and symptoms include:

  • Bleeding from the anus or rectum
  • Pain in the area of the anus
  • A mass or growth in the anal canal
  • Anal itching

When to see a doctor

Talk to your doctor about any signs and symptoms that bother you, especially if you have any factors that increase your risk of anal cancer.



What are the causes for anal cancer?

Anal cancer forms when a genetic mutation turns normal, healthy cells into abnormal cells. Healthy cells grow and multiply at a set rate, eventually dying at a set time. Abnormal cells grow and multiply out of control, and they don't die. The accumulating abnormal cells form a mass (tumor). Cancer cells invade nearby tissues and can separate from an initial tumor to spread elsewhere in the body (metastasize).

Anal cancer is closely related to a sexually transmitted infection called human papillomavirus (HPV). Evidence of HPV is detected in the majority of anal cancers. HPV is thought to be the most common cause of anal cancers.



What are the treatments for anal cancer?

The prognosis (chance of recovery) depends on the following:

  • The size of the tumor.
  • Where the tumor is in the anus.
  • Whether the cancer has spread to the lymph nodes.

The treatment options depend on the following:

  • The stage of the cancer.
  • Where the tumor is in the anus.
  • Whether the patient has human immunodeficiency virus (HIV).
  • Whether cancer remains after initial treatment or has recurred.



What are the risk factors for anal cancer?

Several factors have been found to increase the risk of anal cancer, including:

  • Older age. Most cases of anal cancer occur in people age 50 and older.
  • Many sexual partners. People who have many sexual partners over their lifetimes have a greater risk of anal cancer.
  • Anal sex. People who engage in anal sex have an increased risk of anal cancer.
  • Smoking. Smoking cigarettes may increase your risk of anal cancer.
  • History of cancer. Those who have had cervical, vulvar or vaginal cancer have an increased risk of anal cancer.
  • Human papillomavirus (HPV). HPV infection increases your risk of several cancers, including anal cancer and cervical cancer. HPV infection is a sexually transmitted infection that can also cause genital warts.
  • Drugs or conditions that suppress your immune system. People who take drugs to suppress their immune systems (immunosuppressive drugs), including people who have received organ transplants, may have an increased risk of anal cancer. HIV — the virus that causes AIDS — suppresses the immune system and increases the risk of anal cancer.



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