Diagnosing anal cancer

This page was reviewed under our medical and editorial policy by

Maurie Markman, MD, President, Medicine & Science at CTCA.

This page was updated on June 8, 2022.

Our doctors perform a comprehensive physical exam and a series of diagnostic tests, which are likely to include a biopsy (an anal tissue sample), to diagnose anal cancer.

Other tests for diagnosing anal cancer include:

Digital rectal exam

In a digital rectal exam (DRE), a doctor inserts a gloved finger into the rectum. This may be the first diagnostic test used to evaluate patients with anal cancer. If the doctor feels something suspicious, he or she may order further tests.

CT scan

A CT (computed tomography) scan imaging test helps doctors determine the stage of anal cancer. CT scans are taken throughout treatment to monitor how the cancer is responding to therapy.


A pelvic MRI (magnetic resonance imaging)—using strong magnetic fields and radio waves to produce detailed images—may help doctors stage the cancer. MRI allows for greater soft tissue contrast than a CT scan.

PET scan

A PET (positron emission tomography) scan is a nuclear imaging technique that creates detailed, computerized pictures of organs and tissues inside the body and shows areas of abnormal metabolic activity. A PET scan may be helpful in staging anal cancer, as well as indicating how the patient is responding to treatment.

Next topic: How is anal cancer treated?

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