Anal Cancer

Written by Heaven Stubblefield | Published on September 10, 2013
Medically Reviewed by George Krucik, MD, MBA on September 10, 2013

What Is Anal Cancer?

Anal cancer is when cancer cells form within the tissues of the anus. The anus is the opening at the bottom of the intestines where stools come out of the body. Benign and malignant tumors in this area are signs of anal cancer. Some non-cancerous forms of anal cancer can turn cancerous over time. Anal cancer is rare and may be associated with the spread of cancer in other body parts.

Types of Anal Cancer

There are various forms of anal cancer, which are defined by the types of tumors that develop. Examples include:

  • Benign tumors: Non-cancerous tumors in the anus, they include polyps, skin tags, granular cell tumors, and condylomas.
  • Pre-cancerous conditions: Benign tumors that may become malignant over time, they are common with anal intraepithelial neoplasia (AIN) and anal squamous intraepithelial neoplasia (ASIL).
  • Bowen's disease: Also known as carcinoma in situ, this condition is characterized by abnormal cells on anal surface tissue that have not invaded deeper layers.
  • Squamous cell carcinomas: These are malignant tumors in the anus caused by squamous cells, which are cells that line most of the anal canal. This is the most common type of anal cancer in the U.S. (American Cancer Society, 2013).
  • Basal cell carcinomas: A type of skin cancer affecting areas of the skin exposed to the sun, this is a very rare form of anal cancer.
  • Gastrointestinal stromal tumors: These are anal cancers that are more likely to form in the stomach or small intestines.

What Causes Anal Cancer?

Anal cancer is caused by the development of abnormal cells in the body. These cells can grow uncontrollably. As these abnormal cells accumulate, they form masses known as tumors. Cancer cells can metastasize, or spread through the body, and begin to infect nearby tissues.

Anal cancer is thought to be caused in part by the human papillomavirus (HPV). This is a sexually transmitted disease. It is detected in the majority of anal cancer cases.

Anal cancer may be the result of other cancers in the body spreading through the anal canal.

What Are Risk Factors for Anal Cancer?

Like most cancers, anal cancer can occur in any person. Some patients are more at risk of developing anal cancer than others. Risk factors for anal cancer include:

  • Human papillomavirus infection (HPV): HPV is present in most cases of anal cancer. Having anal sex or more than five sexual partners in a lifetime significantly increases the risk of anal HPV infections.
  • Human immunodeficiency virus (HIV): HIV, the precursor to AIDS, puts patients at a higher risk of anal cancer.
  • Sexual activity: Promiscuity and receptive anal intercourse can increase your risk of getting anal cancer. Not using condoms may also put you at risk.
  • Smoking: Smokers are much more likely to develop cancer of the anus, even if they quit smoking.
  • Weak immune systems: Weakened immune systems may prevent the body from fighting off anal cancer. This is most common in patients who take immune suppressants or who have had an organ transplant.
  • Old age: Most cases of anal cancer occur in patients over the age of 50 (Mayo Clinic, 2013).

What Are the Symptoms of Anal Cancer?

Anal cancer symptoms are similar to those of hemorrhoids, irritable bowel syndrome, and many gastrointestinal diseases. They include changes in bowel habits and bleeding from the rectum. Other symptoms are pain, pressure, or the formation of a lump near the anus. Sometimes, patients may experience discharge from the anus, or itching.

How Is Anal Cancer Diagnosed?

Anal cancer is often spotted early on as it develops in the digestive track. Patients who experience bleeding, itching, or pain in the anus often go to the doctor before anal cancer progresses past stage one. In other cases, anal cancer is diagnosed during routine exams or procedures.

Digital rectal exams can detect some cases of anal carcinoma. These are usually part of prostate exams for men. Manual rectal exams are common for pelvic exams for both genders, where the doctor inserts his or her finger into the anus to feel for lumps or growths.

Anal Pap smears can be used to test for anal cancer. This is similar to a traditional Pap smear. The doctor will use a large cotton swab to collect cells from the anal lining. These cells are then studied for abnormalities.

A doctor may biopsy a set of cells or tissues to test for anal cancer if an abnormality is detected.

How Is Anal Cancer Treated?

There is currently no cure for anal cancer. Doctors prescribe treatment for patients to reduce the spread of cancer cells and the severity of symptoms. Some patients may go into remission with treatment. They are still at risk of developing anal tumors at any time.

Anal cancer treatment is based on the stage of anal cancer a patient has. Common treatments for anal cancer include:

Medications

Chemotherapy is a drug used to kill cancer cells and stop them from growing. It can be injected into the body or taken by mouth. Pain relievers may be used intermittently to control symptoms as well.

Surgeries

Local resection surgery is often used to remove a tumor in the anus, along with some healthy tissue around it. It is most common with patients whose cancer is in the lower part of the anus.

Abdominoperineal resection is a more invasive surgery. An incision is made in the abdomen. The anus, rectum, and parts of the sigmoid colon are removed.

Alternative Therapies

Radiation therapies are common for many forms of cancer, including cancer of the anus. X-rays and other radiations are used to kill cancer cells in the body. This treatment is non-invasive and may be combined with other cancer treatments. 

What Is the Outlook for Anal Cancer?

There is currently no cure for anal cancer. However, many patients are able to live long, healthy lives even after diagnosis. Early detection is the key to sustained health.

According to the Surveillance Epidemiology and End Results (SEER), the overall five-year survival rate for 2003-2009 was 65.6%. Patients with localized anal cancer reported a 79.6% survival rate (SEER, 2013).

Preventing Anal Cancer

There is no guaranteed way to prevent anal cancer. But there are some ways to potentially reduce your risk of anal cancer:
  • Adjust your sexual habits. Limit the number of sex partners you have. Use protection during intercourse. Avoid receptive anal intercourse. Get tested regularly for sexually transmitted diseases.
  • Stop smoking and avoid secondhand smoke.

If you have a high risk of anal cancer due to other factors, such as your family history or age, get tested regularly to catch symptoms at the first stage.

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