Anal Cancer

Anal cancer forms in the anus, the opening at the end of the rectum that helps pass solid waste from the body. Anal cancer is a rare disease, affecting approximately 8,500 people per year in the US according to the American Cancer Society. Anal cancer is diagnosed more often in women than in men. More than 90% of anal cancers are caused by the human papillomavirus (HPV).

Symptoms of anal cancer can include bleeding, itching, or pain when you go to the bathroom, and you may dismiss these as signs of a hemorrhoid (swollen veins in the rectum or anus). While it is true that these symptoms are more likely to be caused by a benign (noncancerous) condition, it is still important to have any instance of anal bleeding checked by a doctor.

There are several different types of anal cancer. Because the anus and the rectum are near each other, sometimes the diagnosis can be confused. It is important to go to a center like Columbia Cancer, where our cancer experts work hand-in-hand with our world-class pathologists to accurately diagnose your cancer and find the best treatments specific to you.

  • Squamous cell carcinoma is the most common type of anal cancer and develops in the cells of the outer lining of the anal canal.
  • Adenocarcinoma develops in the upper part of the anus, in the mucus-producing glands in the anal lining near the rectum.
  • Basal cell carcinoma forms in the skin surrounding the anus.
  • Melanoma is the rarest type of anal cancer and forms in the cells that produce pigments in the lining of the anus.

The American Cancer Society estimates that about 8,500 people are diagnosed with anal cancer each year in the US. The lifetime risk of developing anal cancer is about 1 in 500, and the risk is slightly higher in women than in men.

Can you prevent anal cancer? While most anal cancer is caused by factors you can’t change, you can do these things that have been shown to reduce anal cancer risk in general:

  1. Get the human papillomavirus (HPV) vaccine. HPV infection is a known cause of anal cancer.
  2. Practice safe sex, including using condoms. While condoms provide some protection against HPV, they do not prevent infection entirely.
  3. Stop smoking. Smoking increases your risk for many different types of cancers, including anal cancer.

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Risk Factors

Human papillomavirus (HPV)

More than 90% of anal cancers are caused by human papillomavirus (HPV). HPV is the most common sexually transmitted infection. HPV can lie dormant (not active) in your body, and many people may not even know they have HPV. While HPV is linked with anal cancer, the vast majority of people with HPV do not get anal cancer.

There are more than 150 different subtypes of HPV. HPV-16 is the most common subtype that is found in anal cancers.

Human immunodeficiency virus (HIV)

Those infected with HIV, the virus that causes AIDS, are at a higher risk for getting anal cancer.

Sexual activity

Having multiple sexual partners increases your risk of contracting HIV and HPV, as well as your risk for anal cancer. Having anal sex is also a known risk factor for anal cancer in both women and men.


Smoking can increase your risk for many cancers, including anal cancer. Quitting smoking can help. Former smokers who have quit are at only a slightly higher risk for anal cancer than people who have never smoked.

Lowered immunity

Lowered immunity, including people with AIDS or those taking immune-suppressing drugs for other conditions, are at a slightly higher risk for anal cancer.

Gender and age

Anal cancer is slightly more common in women than men overall. People over 50 are more likely to be diagnosed with anal cancer.

Signs of Anal Cancer

Sometimes there are no symptoms of anal cancer, but minor bleeding is usually the first sign. Many people assume that the bleeding is caused by hemorrhoids, swollen veins in the rectum or anus that can be painful. Hemorrhoids are a common cause of rectal or anal bleeding and are benign.

Symptoms of anal cancer include:

  • Bleeding from the rectum or anus
  • Itching in or around the rectum or anus
  • Pain in the area of the rectum or anus, or a feeling of fullness near the anus
  • A mass or growth in the opening of the anus
  • Abnormal anal discharge

More often than not, many of these symptoms are caused by benign conditions like hemorrhoids, anal warts, or anal fissures. It is still important, however, to always be checked by a doctor if you experience any of these signs.

Screening and Diagnosis

Screening for cancer can help identify a cancer early. Since anal cancer is relatively uncommon in the US, it is not widely recommended for the general public to undergo screening for anal cancer.

However, if you are at an increased risk for anal cancer, you may benefit from screening. If you think you may be at an increased risk, you should reach out to your health care provider about screening. They may recommend an anal Pap test or anal Pap smear, which is much like a Pap test for cervical cancer. The anal lining is swabbed, collecting cells that are analyzed in the lab to identify if cancer cells are present.

If you have symptoms or signs of anal cancer, you should make an appointment to see a health care provider. Your doctor will ask about your symptoms and medical history to understand any risk factors you may have. They will also perform a physical exam, which can include a pelvic exam, a Pap test, and possibly also a digital rectal exam to feel for any lumps in your anus or rectum.

If your doctor finds any problems, they may order other exams or tests to understand more. They may recommend getting an image of your anal canal to see any changes or problems. This may include an ultrasound, X-ray, computed tomography (CT or CAT) scan, or an anoscopy or sigmoidoscopy. An anoscopy uses a thin lighted tube called an anoscope that allows the doctor to see inside the anus or rectum. A sigmoidoscopy is similar to an anoscopy, but uses a small camera instead of a light. These procedures may be done under sedation.

If you have a suspected or confirmed history of HPV infection of the anus, our surgeons may perform high resolution anoscopy, a procedure that allows the examination of the anal canal and the perianal skin to identify and treat anal dysplasia, a common precursor of squamous cell carcinoma.

In order to establish a definitive diagnosis, a biopsy of any suspicious area will be undertaken, which involves a surgeon removing a small piece of tissue (usually under sedation due to the location of anal cancer). A pathologist will then look at the tissue to see if there are any cancer cells present. It is important to have this done by an expert pathologist in order to get the most accurate diagnosis possible. Our pathologists at Columbia Cancer have years of experience in performing such sensitive diagnostic tests as these and work closely with your care team to find the best treatments specific to your cancer.