Many anal cancers can be found early. Early anal cancers often have signs and symptoms that lead people to see a doctor. Unfortunately, some anal cancers may not cause symptoms until they reach an advanced stage. Other anal cancers can cause symptoms like those of diseases other than cancer. This may delay their diagnosis.
Anal cancers develop in a part of the digestive tract that your doctor can easily see and get to. A digital rectal exam (DRE) can find some cases of anal cancer early. In this exam, the doctor inserts a gloved, lubricated finger into the anus to feel for unusual lumps or growths. This test is sometimes used to look for prostate cancer in men (because the prostate gland can be felt through the rectum). The rectal exam is also done routinely as part of a pelvic exam on women.
The odds that anal cancer can be found early depend on the location and type of the cancer. Cancers that begin higher up in the anal canal are less likely to cause symptoms and be found early. Anal melanomas tend to spread earlier than other cancers, making them harder to diagnose them early.
Looking for a disease like cancer in someone with no symptoms is called screening. The goal of screening is to find cancer at an early stage, when treatment is likely to be most helpful. Anal cancer is not common in the United States, so screening the general public for anal cancer is not widely recommended at this time.
Still, some people at increased risk for anal intraepithelial neoplasia (AIN, a potentially pre-cancerous condition) and anal cancer might benefit from screening. This includes men who have sex with men (regardless of HIV status), women who have had cervical cancer, vaginal cancer, or vulvar cancer, anyone who is HIV-positive, and anyone who is immunocompromised (such as people who have received an organ transplant or are on long-term steroids). Some experts also recommend screening for anyone with a history of anal warts and women older than 45 years old who are HPV 16 positive.
For these people, some experts recommend screening with regular anal cytology testing (also known as an anal Pap test or anal Pap smear because it is much like a Pap test for cervical cancer). For an anal Pap test, the anal lining is swabbed, and cells that come off on the swab are looked at closely in the lab. The anal pap test can then be followed by a DRE or a procedure called an anoscopy.
The anal Pap test has not been studied enough to know how often it should be done, or if it actually reduces the risk of anal cancer by catching AIN early. Some experts recommend that the test be done every year in at-risk people who are HIV-positive, and every 2 to 3 years in at-risk people who are HIV-negative. But there is no widespread agreement on the best screening schedule, or even exactly which groups of people can benefit from screening.
Patients with positive results on an anal Pap test should be referred for a biopsy. If AIN is found on the biopsy, it might need to be treated (especially if it is high-grade).
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Last Revised: September 9, 2020