Doctors use various tests to diagnose anal cancer. A colonoscopy may help detect abnormalities in the anus during a routine screening, but doctors do not use it to detect suspected anal cancer.

Anal cancer occurs in the tissue or cells of the skin lining the outside or inside of the anus. The anal canal, or anus, is the short tube opening to the outside of the body. It is the last part of the gastrointestinal tract at the end of the rectum.

This article discusses tests that can help diagnose anal cancer, when someone may need diagnostic tests, and what happens after an anal cancer diagnosis.

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A colonoscopy is a test that allows a doctor to view the rectum and large intestine. It helps find abnormalities in the rectum during screenings for other conditions.

However, doctors do not typically find anal cancer through routine colonoscopies for colorectal cancer. If they find abnormalities during other screenings, they may order other diagnostic tests.

Learn about colonoscopies.

Doctors may recommend different tests to help diagnose anal cancer.

Digital rectal exam

A digital rectal exam involves the doctor inserting a gloved finger into the anus to check for lumps. This test does not confirm a diagnosis of anal cancer, but it allows the medical professional to determine an abnormality and order further tests.


To perform an anoscopy, the doctor inserts a short tube called an anoscope into the anus. Anoscopy allows the doctor to view the lining of the anus and take a tissue sample if necessary.


A proctoscopy involves using a proctoscope to view the rectum and anus. A proctoscope is a thin instrument with a lens and a light.

In some cases, a doctor may remove a tissue sample during a proctoscopy.

Learn more about proctoscopies.


A biopsy involves taking a tissue sample from the anus to examine it under a microscope. The doctor may remove the sample through an anoscopy or proctoscopy.

Learn more about biopsies.

A person with symptoms of anal cancer may need tests to confirm the diagnosis or rule out other possible causes.

About 20% of people with anal cancer may not have symptoms. When symptoms do occur, they can include:

  • bleeding from the anus
  • pain in the anal area
  • a growth at the anal opening
  • a change in bowel habits
  • passing narrow stools
  • mucus, pus, or discharge from the anus
  • swollen lymph nodes in the groin
  • anal itching

Having any one of these symptoms does not mean that a person has anal cancer. It is best to contact a doctor for a diagnosis if a person experiences any of these symptoms.

Learn more about anal cancer.

After an anal cancer diagnosis, doctors may perform additional tests to stage the cancer or determine whether it has spread. These tests can include:

Staging helps the doctor classify how advanced the cancer appears. This plays a role in their treatment recommendations.

Treatment options for anal cancer may include:

Certain factors may increase a person’s risk of developing anal cancer.

Infection with human papillomavirus (HPV) is the biggest risk factor for anal cancer. However, it is important to note that infection with HPV is common, and most cases clear without developing into cancer.

Other risk factors for anal cancer include:

  • having had certain other cancers, such as cancer of the cervix, vagina, or vulva
  • anal warts
  • HIV infection
  • smoking
  • having a reduced immunity

It is best to contact a doctor if a person has concerns about the risk factors for anal cancer.

Doctors may find abnormalities in the anus during a colonoscopy. However, colonoscopies cannot specifically diagnose anal cancer. Doctors do not use a colonoscopy to detect suspected anal cancer.

If a doctor suspects anal cancer, they may order tests such as a digital rectal exam, anoscopy, and proctoscopy.

It is best to contact a doctor as soon as a person has concerns about anal cancer. The doctor can order various tests to confirm the diagnosis and rule out other possible causes of a person’s symptoms.