How Is Anal Cancer Diagnosed?

If you have some of the symptoms of anal cancer, your doctor will begin your diagnosis with a medical history and physical exam.

• Medical history and physical examination - Your doctor will take a complete medical history by asking you about your risk factors, symptoms, and other health problems or concerns. The medical history will focus on the digestive tract—changes in eating habits, changes in bowel movements, abdominal pain or bloating, and how food affects any of the symptoms. The doctor will also do a physical exam to look for signs of anal cancer and other health problems. The doctor will look closely at any uncomfortable areas in your anus and buttocks, masses (lumps) in the anus, enlarged lymph nodes (small bean-shaped organs throughout the body that fight infection), weakness in the ring of muscle that opens and closes the anus (anal sphincter), and loss of feeling around the anus. The doctor will probably order a test to examine your stool for blood.

The doctor may use one of the following methods to visualize the anal canal. He or she will biopsy (remove for examination) any tissue that looks abnormal:

• Anoscopy - The anoscope is a short, lighted tube 3 to 4 inches long and about 1 inch in diameter. The doctor coats the anoscope with a lubricant and gently pushes it into the anus and rectum. By shining a light into this tube, the doctor gets a clear view of the lining of the lower rectum and anus. This is not usually painful.

• Proctoscopy - This is similar to an anoscopy, except that the proctoscope is slightly longer than the anoscope.

• Endoscopy - Your doctor uses a sigmoidoscope (flexible tube attached to a small camera used to examine the lower third of the colon) or a colonoscope (flexible tube attached to a small camera used to examine the entire colon) to look for abnormal growths, bleeding, or other signs of disease.

If your doctor sees something suspicious in your anus, he or she will do a biopsy. This involves cutting out a small piece of tissue and sending it to a laboratory. A pathologist (doctor who specializes in diagnosing diseases) will look at the tissue under a microscope to see whether it has cancerous cells. A biopsy is the only way to be sure whether you have anal cancer. The biopsy might be done by fine needle aspiration or sentinel lymph node biopsy:

• Fine needle aspiration (FNA) - The doctor inserts a thin needle directly into a lymph node (small bean-shaped organ that fights infection) for a few seconds and takes out cells and a few drops of fluid.
   

• Sentinel lymph node biopsy - The doctor injects a radioactive tracer and blue dye around the tumor. The dye and radioactive material travel to the lymph nodes where the cancer is most likely to spread. The surgeon then uses a scanner to find the sentinel lymph node(s), which are the nodes that contain the radioactive substance or are stained with dye. The surgeon takes the sentinel node(s) out to see if they contain cancer cells.

Imaging procedures allow doctors to learn where the cancer is located and whether it has spread from the anus to other areas of the body.

• Chest x-ray - Your doctor might order a chest x-ray to find out whether your anal cancer has spread to the lungs.

• Computed tomography (CT or CAT) scan - Instead of taking one picture, like a conventional x-ray, a CT scanner takes many pictures as it rotates around you. A computer combines these pictures into an image of a slice of your body (like a loaf of sliced bread). CT scans can show tumors within the anal canal as well as the size of the tumor, whether it is growing into nearby tissues, and if it has spread to the liver or other organs.

• Magnetic resonance imaging (MRI) - This procedure uses powerful magnets and radio waves to take detailed cross-sectional images. MRI produces images of cross-sectional slices of your body like a CT scanner. It can also make images of slices that are parallel to the length of your body.

• Positron emission tomography (PET) - Cancer cells use glucose (sugar) more quickly than most other body organs. During a PET scan, the doctor injects a small amount of glucose that has a radioactive atom into your arm. A special camera in the PET machine can detect the radioactivity. This test is useful to see if the cancer has spread. PET scans are often used in combination with information gathered from a CT scan, MRI, and physical examination.

• Endo-anal or endorectal ultrasound - The doctor inserts a small probe (transducer) that looks like a microphone into your rectum. Ultrasound uses sound waves and their echoes to produce a picture of internal organs or masses. This test can show how far the cancer has spread into nearby tissues.

This content has been reviewed and approved by Myo Thant, MD.