Anal Cancer Diagnosis & Staging

MSK pathologist Jinru Shia looks through a microscope

Jinru Shia is part of a team of pathologists who have expertise in diagnosing anal cancer.

Anal Cancer Diagnosis

Anal cancer is often found after symptoms appear. It can be detected in several ways. It may be discovered during a procedure for another condition, such as a hemorrhoid. For people who have a higher risk or who are experiencing symptoms, it may be found during a diagnostic test, such as an endoscopy. Anal cancer is not usually found during a regular screening colonoscopy for colorectal cancer. If anal cancer is suspected, your primary care doctor should refer you to a specialist for additional tests.

Anal cancer is rare. Diagnosing it requires a trained eye. Getting the right diagnosis is an important first step toward successful treatment. MSK’s pathologists and radiologists have extensive experience in performing and analyzing tests for anal cancer. We are committed to giving you a timely, precise diagnosis. When you come to MSK with a suspected diagnosis of anal cancer, our pathologists will make their own assessments of your tests to ensure that your diagnosis is accurate.

How is anal cancer diagnosed?

Medical History

When you go to your primary care doctor with symptoms, the first thing they will do is assess your medical history. They will ask you questions to find out if you have any anal cancer risk factors. They may refer you to a specialist, such as a gastroenterologist.

Digital Rectal Exam and Physical Exam

Your doctor will use a finger to feel for any tumors or abnormalities in your anus and rectum. Other parts of your body may be checked for health problems that are causing your symptoms. Women might need a Pap test or pelvic exam.


During an anoscopy, your doctor will use a small device with a light at the end to help see inside your anus and rectum more clearly. The doctor will look for any lumps or abnormal tissue.

Flexible Sigmoidoscopy

A sigmoidoscopy is used in the same way as an anoscopy. A sigmoidoscopy uses a small camera instead of a light. During this procedure, your doctor may also perform a biopsy, which involves removing a small piece of tissue.


Due to the location of anal cancer, an exam under anesthesia is often needed to obtain a biopsy. During the procedure, your doctor will remove small pieces of tissue. A pathologist will look at the tissue to see if it contains any cancer cells. It is important that an experienced pathologist performs this evaluation so that you get a precise diagnosis. If the pathologist sees cancer cells, advanced tests will be used to determine the type of cancer.

Imaging Tests

If cancer cells are found in your biopsy, your doctor will order imaging tests to see if the cancer has spread to other parts of your body. These may include CT, MRI, or PET scans, or some combination of the three.

If you are diagnosed with anal cancer, your doctor will assign a stage to the cancer. Read more about the stages of anal cancer.