How is anal cancer found?
Many anal cancers can be found early. Early anal cancers often have signs and symptoms (described below) that lead people to see a doctor.
Sometimes anal cancer does not cause any symptoms at all. But anal cancers form in a part of the body that the doctor can see and reach easily, so a rectal exam will still find some cases early. For this exam (called a DRE), the doctor puts a gloved finger into the anus to feel for lumps or growths. A rectal exam may be used to check for prostate cancer in men. For women, the rectal exam is done as part of the pelvic exam.
Sometimes a doctor will find anal cancer during a minor procedure, such as removing a hemorrhoid.
Screening for anal cancer in people at high risk
Looking for a disease like cancer in someone with no symptoms is called screening. It can sometimes find cancer at an early stage, when treatment is likely to be most helpful. Anal cancer is not common in the United States, so doctors don’t advise screening everyone for anal cancer.
Still, some people at increased risk for anal cancer might be helped by screening. This includes:
- Men who have sex with men
- Women who have had cervical cancer or vulvar cancer
- Anyone who is HIV-positive
- Anyone who has had an organ transplant
Some experts also advise screening for anyone with a history of anal warts.
For these people, some experts recommend screening with regular DREs and anal Pap tests. For this test, the anal lining is swabbed, and cells that come off on the swab are looked at under the microscope. The anal Pap test has not been studied enough to know how often it should be done, or even exactly which groups of people can be helped by it.
Signs and symptoms of anal cancer
Some anal cancers cause no symptoms at all. But people who do have symptoms of anal cancer may notice one or more of the following:
- Bleeding or itching around the anus
- A lump at the anal opening
- Pain in the anal area
- Narrowing of stool or other changes in bowel movements
- Swollen lymph nodes in the anal or groin area
- Abnormal discharge from the anus
These symptoms can also be caused by something other than cancer, but only your doctor can tell for sure. Talk to your doctor right away if you notice any of these problems.
Medical history and physical exam
If you have symptoms that might be caused by anal cancer, your doctor will ask about your medical history to check for possible risk factors and to learn more about your symptoms.
Your doctor will also check you for possible signs of anal cancer or other health problems. He or she will probably do a rectal exam.
Tests for anal cancer
If anything abnormal is found during your exam, your doctor might do other exams or tests to help find the problem. If you are being seen by your primary care doctor, you might be referred to a proctologist (a doctor who treats diseases of the colon, rectum, and anus) for further tests.
Endoscopy is the use of a tube with a lens or tiny video camera on the end (called a scope) to look inside the body. Endoscopy may be used to look for the cause of anal symptoms. It can also be used to get biopsy samples from inside the anus (described below). For these tests you either lie on your side on an examining table, with your knees bent up to your chest, or you bend forward over the table.
Anoscopy: For this test, the doctor coats the anoscope (a hollow tube about 4 inches long) with a lubricant and then gently pushes it into the anus and rectum. By shining a light into this tube, the doctor has a clear view of the lining of the lower rectum and anus and sometimes the lower part of the colon. This exam is usually not painful.
Rigid proctosigmoidoscopy: The rigid proctosigmoidoscope is similar to an anoscope, except that it is about 10 inches long, so it lets the doctor see the rectum as well as the lower part of the colon. You will most likely need to take laxatives or have an enema before the test to make sure your bowels are empty.
In order to find out if a growth is cancer, a biopsy must be done. For a biopsy, the doctor removes a sample of tissue and sends it to a lab to be looked at under a microscope. For anal cancer, this tissue sample is most often removed during endoscopy. If the tumor is very small and has not grown below the surface of the anus, your doctor may be able to take out the whole tumor during the biopsy.
Biopsies to check for cancer spread to nearby lymph nodes
Anal cancer sometimes spreads to nearby lymph nodes (bean-sized collections of immune system cells). Swollen lymph nodes in the groin can be a sign of spreading anal cancer. Most often, though, they are a sign of infection.
Fine-needle aspiration (FNA) biopsy: For this test, a small (fine), hollow needle is placed into the swollen node to remove some cells and fluid that is then sent to the lab. If cancer is found in a lymph node, an operation to remove the nearby lymph nodes may then be done.
Sentinel lymph node biopsy (SLNB): If anal cancer has already been found, this test might be used to help see if the cancer has spread to the lymph nodes. In this test, a radioactive substance, often with a blue dye, is injected around the tumor. The dye will move into the nodes that carry fluid away from the tumor. These would be the nodes that any cancer cells leaving the tumor would have spread to first. These nodes are removed and examined to see if they contain cancer cells. This helps tell how far the cancer may have spread. While this test has been shown to be useful for some other cancers, it’s not yet clear how helpful it is for anal cancer.
Imaging tests create pictures of the inside of your body. They might be done for a number of reasons, including:
- To help find areas of cancer
- To learn how far cancer has spread
- To help tell if treatment is working
- To look for signs of cancer coming back after treatment
Some of these imaging tests are used more often than others.
Ultrasound uses sound waves to make pictures of the inside of the body. This test can be used to see how deep the cancer has grown into the tissues around the anus. For anal cancer, a probe must be placed in the rectum, which can be slightly uncomfortable but should not be painful.
CT scan (computed tomography)
A CT scan use x-rays to make detailed images of your body. This is a common test for people with anal cancer. It can help tell whether the cancer has spread to nearby lymph nodes or to distant organs such as the liver or lungs.
The CT scan machine moves around you and uses x-rays to take many pictures of the body. A computer then combines them to make pictures of cross-sections of the body.
A CT scanner has been described as a large donut, with a narrow table that slides in and out of the middle “hole”. You will need to lie still on the table while the scan is being done.
Before any pictures are taken, you may be asked to drink a liquid called oral contrast. If you are having any trouble swallowing, tell your doctor before the scan. You may also get an IV (intravenous) line for a different kind of contrast dye. Some people are allergic to the contrast. Be sure to tell your doctor if you have any allergies or have ever had such a reaction.
CT scans can also be used to guide a biopsy needle into a tumor.
MRI (magnetic resonance imaging)
MRI uses radio waves and strong magnets instead of x-rays to make detailed pictures. This test is sometimes used to see if nearby lymph nodes are enlarged, which might be a sign the cancer has spread there.
MRI scans take longer than CT scans, often up to an hour. Also, you have to lie inside a narrow, tube-like machine, which upsets some people. Special, more open MRI machines can sometimes help with this if needed.
This test might be done to see whether the anal cancer has spread to the lungs. It isn’t needed if a CT scan of the chest is done.
PET scan (positron emission tomography)
For a PET scan, a special radioactive chemical (called a radiotracer) is put into a vein. Cancer cells quickly take up the tracer. Then a scanner can spot those areas. PET scans look for cancer in the whole body. They are useful when the doctor thinks the cancer might have spread but doesn’t know where. Special machines combine a PET scan with a CT scan.
For more on scans and x-rays, see our document Imaging (Radiology) Tests.
Last Medical Review: 06/10/2014
Last Revised: 01/20/2016