Diagnosis and staging of anal cancer

How is it diagnosed?

Your GP will take a history of your health and current symptoms. S/he is likely to do a physical examination of the abdomen, and a detailed visual and digital examination (using a gloved finger) of the anus and rectum (back passage). S/he may also request a blood test to check for anaemia and any underlying health problems. If your GP suspects that you may have cancer, s/he will refer you urgently to a hospital colorectal specialist for diagnosis.

Special tests at the hospital may include:

  • Proctoscopy – insertion of a short, illuminated tube for looking into the rectum.
  • Ultrasound scan using a probe inserted into the rectum.
  • Biopsy of any abnormal lumps or tissue for microscopic examination (usually under general anaesthetic as this is more comfortable).

If the test results show any suspicious findings you will then be referred for a colonoscopy, a CT scan of chest, abdomen and pelvis and a pelvic MRI (magnetic resonance imaging) scan to help your specialist plan the treatment that is best for you.


Staging and grading of anal cancer

Anal cancer tumours usually remain within the anal canal. However, cancer cells can spread beyond the tissue of the anus, via the blood stream and/ or lymphatic system, throughout the body and most often to the liver and lungs. The lymphatic system is a network of glands (nodes) linked by fine ducts that transport lymph fluid, as part of the body’s defences against disease and infection. When cancer cells enter the lymph nodes, it can cause them to swell, which is why they are checked as part of the cancer staging investigations. Anal cancer can also spread locally and invade other pelvic organs such as the vagina, prostate gland or bladder. Knowing what stage a cancer is at will help the doctors decide on the most appropriate treatment pathway for you.


Stage 0: also known as anal carcinoma in situ (AIN) or Bowen’s disease.

Stage 1: the cancer only affects the anus and is smaller than 2cm in size. It has not begun to spread into the sphincter muscle.

Stage 2: The cancer is bigger than 2cm in size, but has not spread into the lymph nodes or other parts of the body.

Stage 3: The cancer has spread into the lymph nodes, or to nearby organs such as the vagina or bladder.

Stage 4: The cancer has spread to other more distant parts of the body, e.g. the liver.


Your consultant will probably use the more complex TNM method of describing your cancer:

Tumour: the stage of the tumour and whether it has spread to the lymph nodes

Nodes: the extent to which the lymph nodes are involved

Metastases: the extent of spread to other organs (also known as secondaries).