Diagnosis of anal cancer

Diagnosis is the process of finding out the cause of a health problem. Diagnosing anal cancer usually begins with a visit to your family doctor. Your doctor will ask you about any symptoms you have and do a physical exam. Based on this information, your doctor may refer you to a specialist or order tests to check for anal cancer or other health problems.

The process of diagnosis may seem long and frustrating. It's normal to worry, but try to remember that other health conditions can cause similar symptoms as anal cancer. It's important for the healthcare team to rule out other reasons for a health problem before making a diagnosis of anal cancer.

The following tests are commonly used to rule out or diagnose anal cancer. Many of the same tests used to diagnose cancer are used to find out the stage, which is how far the cancer has progressed. Your doctor may also order other tests to check your general health and to help plan your treatment.

Health history and physical exam

Your health history is a record of your symptoms, risk factors and all the medical events and problems you have had in the past. Your doctor will ask questions about your history of:

  • symptoms that suggest anal cancer

  • human papillomavirus (HPV) infection
  • certain sexual behaviours, including the number of sexual partners and having anal sex
  • infection with the human immunodeficiency virus (HIV)
  • other risk factors for anal cancer

Your doctor may also ask about a family history of:

  • anal cancer
  • risk factors for anal cancer
  • other cancers

A physical exam allows your doctor to look for any signs of anal cancer. During a physical exam, your doctor may:

  • examine the anal area for any abnormal skin, redness or lumps
  • do a digital rectal exam (DRE) check for any lumps or swelling
  • feel the groin for swelling or enlarged lymph nodes
  • do a pelvic exam and Pap test to check the health of the vagina and cervix

Find out more about physical exam.

Complete blood count (CBC)

A CBC measures the number and quality of white blood cells, red blood cells and platelets. A CBC is done to check for anemia from long-term, or chronic, bleeding from the anus or rectum.

Find out more about complete blood count (CBC).

Blood chemistry tests

Blood chemistry tests measure certain chemicals in the blood. They show how well certain organs are working and can help find problems. Blood chemistry tests used to stage anal cancer and check your overall health include the following.

Liver function tests measure how well the liver is working. Higher levels of certain substances may mean that anal cancer has spread to the liver.

Kidney function tests are used to check how well the kidneys are working.

Find out more about blood chemistry tests.


Endoscopy allows a doctor to look inside body cavities using a flexible tube with a light and lens on the end. This tool is called an endoscope. Doctors usually do an endoscopy if they feel an abnormality during a DRE. It is also used to find out what is causing certain symptoms such as bleeding from the anus or rectum. A biopsy can be done during endoscopy.

Different types of endoscopy may be done to diagnose anal cancer and help determine the stage. They are named for the structures or organs they examine.

Anoscopy allows a doctor to look inside the anal canal and end of the rectum using an anoscope.

Proctoscopy is used to examine the entire rectum.

Sigmoidoscopy is done to examine the rectum and sigmoid colon (the last part of the colon).

Doctors may use a proctoscopy or sigmoidoscopy instead of an anoscopy to find out if anal cancer has grown into the rectum.

Find out more about endoscopy.


During a biopsy, the doctor removes tissues or cells from the body so they can be tested in a lab. The report from the lab will confirm whether or not cancer cells are present in the sample.

A biopsy is usually done during an endoscopy (called an endoscopic biopsy). Doctors will remove small amounts of tissue or polyps from the anus, rectum or both.

Fine needle aspiration may be done to check for cancer in enlarged lymph nodes in the groin. The doctor uses a very thin needle and syringe to remove a small amount of fluid or cells from a lymph node.

Find out more about biopsy and fine needle aspiration.

Transrectal ultrasound (TRUS)

Ultrasound uses high-frequency sound waves to make images of structures in the body. During TRUS, an ultrasound transducer, or probe, is passed through the anus and into the rectum. Sometimes the probe is only put inside the anal canal. This is called an endoanal ultrasound.

TRUS is used to find out the stage of the anal cancer. It can show doctors the size of the tumour and if the cancer has spread to the anal sphincter, to the vagina (in women) or to the prostate (in men).

Find out more about transrectal ultrasound (TRUS).

CT scan

A computed tomography (CT) scan uses special x-ray equipment to make 3-D and cross-sectional images of organs, tissues, bones and blood vessels inside the body. A computer turns the images into detailed pictures.

A CT scan is used to check if anal cancer has spread to lymph nodes or organs in the chest, abdomen and pelvis.

Find out more about CT scan.


Magnetic resonance imaging (MRI) uses powerful magnetic forces and radiofrequency waves to make cross-sectional images of organs, tissues, bones and blood vessels. A computer turns the images into 3-D pictures.

MRI may be used to check if anal cancer has spread to lymph nodes and organs in the abdomen and pelvis, particularly lymph nodes in the groin.

Find out more about MRI.

Chest x-ray

An x-ray uses small doses of radiation to make an image of the body’s structures on film. A chest x-ray is used to check if anal cancer has spread to the lungs.

Find out more about x-ray.

PET-CT scan

A positron emission tomography (PET) scan uses radioactive materials called radiopharmaceuticals to look for changes in the metabolic activity of body tissues. A computer analyzes the radioactive patterns and makes 3-D colour images of the area being scanned.

A PET-CT scan combines PET scan and a CT scan so they are done at the same time using the same machine. It may be used to help stage anal cancer and check if it has spread to lymph nodes or organs in the chest, abdomen and pelvis. Your healthcare team may also use PET-CT scan to help plan surgery.

Find out more about PET scan.

Human immunodeficiency virus (HIV) testing

People with HIV can be at risk for developing anal cancer. If your healthcare team thinks you have anal cancer or if you have been diagnosed with anal cancer, they may order a blood test to see if you have an HIV infection.

HIV infects a type of cell called CD4. CD4 is a type of T cell, which is a type of white blood cell, or lymphocyte. Low CD4 counts mean that you may get infections more easily, so getting a a CD4 count is done for people with anal cancer that have an HIV infection. The CD4 count helps your healthcare team plan your treatment.

Questions to ask your healthcare team

To make the decisions that are right for you, ask your healthcare team questions about diagnosis.

Expert review and references

  • American Cancer Society. Anal Cancer Early Detection, Diagnosis, and Staging. 2020: https://www.cancer.org.
  • Czito BG, Ahmed S, Kalady MF, Eng C. Cancer of the anal region. DeVita VT Jr., Lawrence TS, Rosenberg SA, eds. DeVita, Hellman, and Rosenberg's Cancer: Principles & Practice of Oncology. 11th ed. Philadelphia, PA: Wolters Kluwer; 2019: 64:997–1013.
  • National Comprehensive Cancer Network . NCCN Clinical Practice Guidelines in Oncology: Anal Carcinoma Version 1.2022 . 2022.
  • Rao S, Guren MG, Khan K, et al. Anal cancer: ESMO Clinical Practice Guidelines for diagnosis, treatment and follow-up. Annals of Oncology. 2021: 32(9):1087–1100.
  • Gondal TA, Chaudhary N, Bajwa H, Rauf A, Duc L, Ahmed S. Anal cancer: the past, present and future. Current Oncology. 2023: 30(3):3232–3250.

Medical disclaimer

The information that the Canadian Cancer Society provides does not replace your relationship with your doctor. The information is for your general use, so be sure to talk to a qualified healthcare professional before making medical decisions or if you have questions about your health.

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