Anal cancer affects the cells lining the anus, which is the opening at the end of the rectum where feces leave the body. When the cells in the anal lining become abnormal and grow out of control, they can become cancerous.

Anal Cancer Symptoms

• Most anal cancers are asymptomatic
• Pain or itching in the anus
• Bleeding from the anus
• A growth or bump in the anus

Some of these signs and symptoms can also be due to noncancerous conditions such as hemorrhoids, polyps, skin tags and anal warts. Some benign tumors can affect the anus. A doctor can help rule out a precancerous or cancerous growth.

Anal Cancer Causes

There is a relationship between HPV (human papillomavirus) infection and anal cancer. HPV is the most common sexually transmitted infection. Nearly 80 million Americans are currently living with some type of HPV. There are more than 150 types of HPV, and types 16 and 18 cause almost 90% of anal precancerous lesions and anal cancers.

HPV can cause genital and anal warts. Nine out of 10 HPV infections go away on their own. But if the infection becomes persistent or more severe due to a weakened immune system, such as in people receiving transplant therapy or living with HIV, HPV can cause cancers later in life, including anal cancer.

HPV vaccines can prevent infection by specific types of HPV and are best given before a person gets exposed or infected. The Advisory Committee on Immunization Practices of the Centers for Disease Control and Prevention (CDC) recommends that all adolescents and young adults up to age 26 receive an HPV vaccine, ideally before they become sexually active. However, some people between the ages of 27 and 45 may also benefit from the HPV vaccine. Your primary care provider can discuss whether you potentially could benefit from the HPV vaccine.

Anal Cancer Risk Factors

The way that cells of the anus change into cancer is not fully understood. However, there are factors that can increase the risk for anal cancer, mainly by increasing the risk that HPV infection becomes persistent. These factors include:

• Multiple sex partners
• Having anoreceptive intercourse (anal sex)
• Smoking
• A history of anal warts
• A history of precancer or cancer of the cervix, vagina, vulva or penis (these are often caused by HPV)
• HIV infection
• Age over 50
• Organ transplantation
• Immunosuppressed conditions, such as those due to medications (steroids, biologic therapy, etc.)

Anal Cancer Diagnosis

Several tests can help your doctor determine if you have anal cancer or anal dysplasia.

Anal Pap test: A swab is inserted into the anus to obtain cells for a pathologist to evaluate for cancer.

Digital rectal exam: The doctor or nurse inserts a lubricated, gloved finger into the anus and feels for bumps or lumps.

Anoscopy: Using a lighted tube, the doctor checks the anus and rectum for suspicious areas in the anal canal.

High resolution anoscopy (HRA): The doctor examines the anus and rectum using a lighted tube and evaluates suspicious areas in the anal canal by using stains.

Anal Biopsy

If the doctor sees or feels an abnormal spot, he or she may numb that area and remove a tissue sample to send to a pathology lab. There, doctors look at the sample under a microscope to see if the cells are abnormal.

The biopsy may cause temporary discomfort and bleeding once the numbing medicine wears off. Having a bowel movement may make the pain worse. The doctor can recommend ways to obtain relief, encourage healing and prevent infection of the biopsy area.

Anal Cancer Staging

If anal cancer is present, the cancer needs to be staged. Staging indicates how advanced or aggressive the cancer is and helps doctors determine the most appropriate treatment. Diagnostic studies may include a computerized tomography (CT) scan of the chest, abdomen, pelvis and a positron emission tomography (PET) CT.

Treatment of Anal Precancer and Anal Cancer

Some precancerous areas such as high-grade anal dysplasia may be treated topically or with heat ablation in the doctor’s office.

For carcinoma in situ (car-sin-OH-mah in SY-too) or more advanced anal cancers, patients may be referred to a surgeon. Invasive anal cancer that has spread in the body is treated with chemotherapy and radiation.

After treatment for anal dysplasia or anal cancer, it is important for the patient to get regular checkups to ensure the cancer doesn’t return.

What Happens During Anal Cancer Screening

Screening for anal cancer is not recommended for the general population. However, some people who are at very high risk for developing anal cancer may benefit from being screened, even if they do not have any anal symptoms. Your doctor can discuss with you whether you would benefit. The goal of anal cancer screening is to detect anal dysplasia and abnormalities in the anus that are not cancer yet but may progress to cancer.

The first step in anal cancer screening is usually a digital rectal examination, which may be followed by a Pap test. At Johns Hopkins’ HRA clinic, practitioners perform an anal Pap test followed by a digital rectal exam.

Pap Test (Pap Smear) for Anal Cancer and Anal Dysplasia

Very similar to a cervical Pap test, during an anal Pap test a Dacron swab is used to collect cells from the anus. A pathologist studies them under a microscope and results are categorized as:

• Benign or normal — there are no abnormal changes in the cells and no treatment is needed. The anal Pap test should be repeated in six to 24 months, depending on what risk factors you have.
• Unsatisfactory or inadequate — the specimen collected was not adequate, and your provider will likely recommend a repeat anal Pap test during your next appointment.
• Atypical squamous cells of unknown significance — the cells are abnormal, but no definitive diagnosis can be made. These changes are noncancerous and may be caused by inflammation or may be associated with dysplasia. HRA is recommended.
• Atypical squamous cells, cannot exclude high-grade lesion (ASC-H) — the cells are abnormal but the changes are probably precancerous. HRA is definitely indicated, but you might not need any treatment.
• Low-grade squamous intraepithelial lesion (LSIL): Mild dysplasia. LSIL could mean that you have anal warts or there could be pre-cancerous areas. HRA is indicated, but you might not need any treatment.
• High-grade squamous intraepithelial lesion (HSIL) — moderate to severe dysplasia. The cells in the anus show changes most likely caused by HPV infection. This is a sign that you probably have a precancerous area in your anus, but it does not mean you have cancer. HRA is definitely indicated, and you may be referred for treatment.
• Squamous carcinoma — in this very rare occurrence, the cells show severe changes that are very suspicious of a cancer, calling for immediate HRA or referral to a surgeon.

If your anal Pap test has any abnormal results, your doctor may discuss referring you to a specialist who can perform an HRA to take a better look at the anal canal. Sometimes during HRA, a biopsy is taken to provide more information on whether you have anal dysplasia.

High-Resolution Anoscopy (HRA)

High-resolution anoscopy or HRA is a screening tool used to detect anal dysplasia or cancer.

During high-resolution anoscopy, a doctor performs an anal Pap test and then uses an anoscope (a device shaped like a plastic tube just larger than a finger) to look into the anal canal. A second device called colposcope is used to examine tissues under magnification, after special reactive agents are applied to highlight suspicious areas. A small piece of anal tissue (biopsy) is collected from abnormal areas. This procedure takes 15-30 minutes.