Are you experiencing bowel-related symptoms you feel unable to discuss with anyone? Symptoms like bleeding “down below” or unpleasant diarrhea? If you are, don’t ignore them, because they could signal colorectal or anal cancer. “Unfortunately, people often do feel embarrassed about discussing lower digestive tract issues with their doctor, and they also may be mistaken for less serious complaints, such as hemorrhoids,” says Mount Sinai gastroenterologist Brijen J. Shah, MD.
Colorectal cancer is common in older age, but you can avoid it by following your doctor’s advice for colorectal cancer screening. “Anal cancer is much less common,” notes Dr. Shah. “However, if you are in a high-risk group for this disease, it is vital to tell your doctor about any symptoms that could indicate anal cancer.”
What Is Anal Cancer?
Anal cancer is cancer that originates in the very lowest part of the digestive tract, where the rectum meets the external part of the body. This area is called the anus, and tissues there are composed of different types of cells than those that form the colon. All cells can develop cancer-causing mutations; however, certain types of anal cancer are more common.
How Common Is Anal Cancer?
Anal cancer is rare— the American Cancer Society estimates that there will be about 11,270 new cases in 2026. The disease is more common in middle-aged and older adults, with the early 60s being the average age at diagnosis. Studies suggest that women are slightly more vulnerable than men.
“The number of people who die from anal cancer each year has been increasing,” Dr. Shah says. “Even so, treatment often is effective, particularly if the disease is detected early in its course.”
Symptoms of Anal Cancer
The most common anal cancer symptoms include bleeding (typically bright red blood), a lump on or near the anus, a feeling of fullness in the area that is not relieved by a bowel movement, pain during bowel movements, pain and/or itching around the area, and discharge from the anus.
There also may be a change in bowel habits. For example, you may begin to find it difficult to control bowel movements and may pass stools that are narrower than normal. “I cannot emphasize enough that bleeding from the colorectal canal always warrants a call to your doctor, no matter how embarrassed you may be to talk about things you consider personal,” Dr. Shah says. “Bleeding is probably the most common early sign of anal cancer and also can signal colorectal cancer. Alerting your doctor makes it more likely you will be diagnosed early enough for treatment to be successful.”
Causes of Anal Cancer
A major cause of anal cancer is infection with human papillomavirus (HPV). Low-risk HPV infections resolve spontaneously in nine out of 10 cases. High-risk HPV is more likely to persist and cause cellular abnormalities that eventually progress to anal cancer.
“Low-risk HPV is most likely to cause visible anal and vaginal warts, while high-risk HPV strains often do not cause warts,” Dr. Shah says. “However, it is possible to have low-risk and high-risk versions of HPV simultaneously.” High-risk HPV also is associated with cancers of the cervix, throat, and vagina, among others.
Risk Factors for Anal Cancer
Anal cancer risk factors include advancing age, a trait shared by most cancers. “This is because it often takes decades for abnormal cells to become cancerous,” Dr. Shah explains. “Moreover, the immune system weakens in older age, which can make it harder for immune cells to eradicate HPV or destroy cancer cells.”
He adds that immunity also may be affected by infection with human immunodeficiency virus (HIV) and by the use of immunosuppressant drugs to manage autoimmune diseases like rheumatoid arthritis and prevent organ transplant rejection.
Other risk factors for anal cancer include:
- Unprotected sex and anal sex with multiple partners, which increases your risk of infection with HPV and HIV.
- Previous HPV-related cancers, including cervical cancer, throat cancer, and cancers of the vulva, vagina, and penis.
- Chronic irritation of the anus, which may be related to anal fissures and fistulas. The former is a tear in the lining of the anal canal, and latter is a channel that develops between the anal canal and the skin or another organ, such as the vagina). Constipation can raise the risk of anal fissures, while fistulas occur most often in people with Crohn’s disease, cancer, or HIV.
- Smoking, which raises the risk for numerous cancers by damaging cells and impairing your immune response.
How Anal Cancer Is Diagnosed
A range of options is available for diagnosing anal cancer in symptomatic people. The most basic include a careful visual examination of the anal area and a digital rectal exam, during which your doctor will insert a gloved finger into the anal canal and feel for abnormal growths. Dr. Shah says that an anal Pap test also may be performed. “Similar to the pap test that is used to screen for cervical cancer, the test uses a swab to collect cells from the anus that are then examined in a lab to check for abnormalities,” he explains.
If initial tests are concerning, a high-resolution anoscopy may be recommended. During this test, an anoscope (a small viewing scope with a light at the tip) is inserted into the anal canal so that your doctor can more closely inspect any masses and look for other potential symptoms, such as warts and areas of inflammation. Tissue samples (biopsies) may be taken during this procedure and sent to a lab for analysis.
If an anal cancer diagnosis is made, the next steps may be additional testing or you and your healthcare provider may start to map out a personalized treatment plan.
Types and Stages of Anal Cancer
You may have heard of some types of anal cancer because they also are skin cancers. One of them—squamous cell carcinoma—accounts for up to 90% of anal cancers. Closely associated with HPV, it develops in the flat cells that line the anal canal. “Rarely, melanoma and basal cell carcinoma can affect the anus, too,” Dr. Shah adds. “In the case of basal cell carcinoma, the cancer occurs in the skin surrounding the anal region.”
Other less common types of anal cancer are adenocarcinoma, which affects anal glands, gastrointestinal stromal tumors (GISTs), and neuroendocrine tumors. “GISTs are extremely rare and have strong genetic risk factors,” Dr. Shah says. “Neuroendocrine tumors also are very rare, and are more likely to affect younger people and people of Black or Asian descent. Neither GISTs nor neuroendocrine tumors share the same risk factors as the more common types of anal cancer.”
When cancer is confirmed by initial tests, imaging tests—including ultrasound, computed tomography scans, and positron emission tomography—are used to categorize the disease into stages 0 through IV. “Put simply, staging essentially is an evaluation of how large a tumor is and whether cancer cells have spread beyond their initial site,” Dr. Shah explains. “Staging can give you and your doctor useful information about what treatments are most likely to help you and often is repeated during treatment to monitor your response.”
Anal cancer staging is based on the following determinations:
- Stage 0 indicates that abnormal cells have been detected in the lining of the anal canal.
- Stage I is a tumor less than 2 centimeters (cm) in diameter that has not spread.
- Stage II is tumor with a diameter exceeding 2 cm and no spread.
- Stage III is a tumor of any size that has spread to nearby lymph nodes, body tissue, and/or organs.
- Stage IV reflects cancer that has spread to distant parts of the body. The liver is the most likely distant organ to be affected by anal cancer, followed by the lungs.
Treatment Options for Anal Cancer
As with any cancer, anal cancer treatment depends on the size of the tumor, and its spread. Dr. Shah says that a combination of chemotherapy and radiation is most often used, while surgery may be carried out to remove small tumors that are detected before they have spread and tumors that recur after chemoradiation treatment.
People with cancer that has not responded to other treatments and/or advanced cancer that has spread elsewhere in the body may be treated with immunotherapy and targeted therapy. “Immunotherapy drugs help your immune system recognize and destroy cancer cells, while targeted therapy attacks specific molecules or processes inside cancer cells that help the cells grow,” Dr. Shah explains.
Prognosis and Survival Rates
Here’s the good news: most anal cancer can be successfully treated if it is diagnosed early in the course of the disease. If a tumor is detected when it is confined to the anal area, the five-year anal cancer survival rate is about 85%. This drops to 70% if the cancer spreads to nearby tissues or lymph nodes. However, it is a distant spread that really impacts your prognosis. If the cancer is found in distant organs, the five-year anal cancer survival rate is about 36%. “What this makes clear is that it is so important to see your doctor for any symptoms that could signal anal cancer or the much more common colorectal cancer, which also causes bleeding from the digestive tract,” Dr. Shah observes. “It is common for patients to feel self-conscious about discussing bleeding from ‘down there,’ but we really have seen and heard it all before.”
If you are really struggling to explain your symptoms to your doctor, Dr. Shah recommends writing them down and giving the note to your doctor. “This will prompt them to ask you the right questions so that you don’t have to broach the topic yourself,” he says.
Prevention and Reducing Your Risk
Getting vaccinated against HPV is one of most important steps in anal cancer prevention and the prevention of other cancers that are strongly associated with HPV. The vaccine is mainly aimed at children ages 11 through 16, and immunocompromised people ages 9 to 26. HPV vaccination is not recommended for people older than 26; however, individuals ages 27 to 45 years may get the vaccine if they did not get vaccinated when they were younger. Speak with your doctor to find out more.
Routine screening for people who are symptomatic and low risk for anal cancer is not recommended in the United States. However, people at high risk for the disease should ask their doctor about getting screened. Anal cancer prevention should be a priority for high-risk groups, which include men who have sex with men, women who have had cervical or vulvar cancer, people living with HIV, and those who have had an organ transplant. Screening may involve regular digital rectal exams and anal Pap tests.
Living With and Beyond Anal Cancer
Cancer treatment isn’t as harsh as it used to be, but it still can be taxing. Fatigue is a common side effect of treatment, and radiation may cause temporary skin irritation around and inside the anus and on the buttocks. Radiation also can cause diarrhea and make bowel movements and/or urination painful. Most side effects do improve after your course of treatment ends.
You also likely will feel anxious about your prognosis. Reaching out to other people who have gone through the same experience can be helpful in terms of emotional support and strategies to help you manage treatment side effects. Some self-help measures during and after treatment you can try include:
- Avoiding soap and scented shower gels—instead, wash your anal area with plain lukewarm water.
- Using a barrier cream to soothe and protect sore skin—ask your doctor to recommend or prescribe one.
- Asking your doctor for anti-nausea medication if chemotherapy drugs make you feel ill.
- Eating smaller meals more frequently if nausea is affecting your appetite and avoiding spicy and high-fiber foods that may worsen diarrhea.
- Staying hydrated, especially if you experience diarrhea.
Keep in mind that you will be closely monitored for recurrence after your treatment ends. Studies suggest that recurrence is most likely within two years of an initial diagnosis. “During this time, you will see your doctor every three to six months for digital rectal exams and other tests recommended by your doctor,” says Dr. Shah. “Above all, immediately call your doctor if you experience any symptoms that could indicate that your cancer has returned.”
