Anal Cancer: Diagnosis

Approved by the Cancer.Net Editorial Board, 03/2015

ON THIS PAGE: You will find a list of the common tests, procedures, and scans that doctors can use to find out what’s wrong and identify the cause of the problem. To see other pages, use the menu on the side of your screen.

Doctors use many tests to diagnose cancer and find out if it has spread to another part of the body, called metastasis. Some tests may also determine which treatments may be the most effective. For most types of cancer, a biopsy is the only way to make a definitive diagnosis of cancer.

If a biopsy is not possible, the doctor may suggest other tests that will help make a diagnosis. Imaging tests may be used to find out whether the cancer has spread.

This list describes options for diagnosing this type of cancer. Not all tests listed will be used for every person. Your doctor may consider these factors when choosing a diagnostic test:

  • Age and medical condition
  • Type of cancer suspected
  • Signs and symptoms
  • Previous test results

In addition to a physical examination, the following tests may be used to diagnose anal cancer:

  • Digital rectal examination (DRE). During this test, the doctor inserts a gloved finger into the anus to feel for lumps or other abnormalities. General cancer guidelines suggest men have a DRE annually after the age of 50 and women have one during routine pelvic examinations. If you are at higher risk for developing anal cancer, your doctor may perform a DRE more often.
  • Anoscopy. If the doctor feels a suspicious area during a DRE, this endoscopic test may be performed to take a closer look at the area. An anoscopy allows the doctor to see inside the body with a thin, lighted, flexible tube called an anoscope. Similarly, a proctoscope can be used to view the rectum in a procedure called a proctoscopy. The person may be sedated as the tube is inserted into the anus and/or rectum.
  • Biopsy. A biopsy is the removal of a small amount of tissue for examination under a microscope. Other tests can suggest that cancer is present, but only a biopsy can make a definite diagnosis. A pathologist then analyzes the sample(s). A pathologist is a doctor who specializes in interpreting laboratory tests and evaluating cells, tissues, and organs to diagnose disease. The type of biopsy performed will depend on the location of the tumor. For instance, an excisional biopsy can remove the entire lump if the lump is small and has not grown into other tissues. Lymph nodes may also be removed and examined in a biopsy.
  • Ultrasound. An ultrasound uses sound waves to create a picture of the internal organs. In an anal ultrasound, an ultrasound wand is inserted into the anus to obtain the pictures.
  • X-ray. An x-ray is way to create a picture of the structures inside of the body using a small amount of radiation.
  • Computed tomography (CT or CAT) scan. A CT scan creates a three-dimensional picture of the inside of the body with an x-ray machine. A computer then combines these images into a detailed, cross-sectional view that shows any abnormalities or tumors. A CT scan can also be used to measure the tumor’s size. Sometimes, a special dye called a contrast medium is given before the scan to provide better detail on the image. This dye can be injected into a patient’s vein or given as a pill to swallow.
  • Magnetic resonance imaging (MRI). An MRI uses magnetic fields, not x-rays, to produce detailed images of the body. A special dye called a contrast medium is given before the scan to create a clearer picture. This dye can be injected into a patient’s vein or given as a pill to swallow.
  • Positron emission tomography (PET) scan. A PET scan is a way to create pictures of organs and tissues inside the body. A small amount of a radioactive sugar substance is injected into the patient’s body. This sugar substance is taken up by cells that use the most energy. Because cancer tends to use energy actively, it absorbs more of the radioactive substance. A scanner then detects this substance to produce images of the inside of the body.

After diagnostic tests are done, your doctor will review all of the results with you. If the diagnosis is cancer, these results also help the doctor describe the cancer; this is called staging.

The next section in this guide is Stages and Grades, and it explains the system doctors use to describe the extent of the disease. Or, use the menu on the side of your screen to choose another section to continue reading this guide.