Anal Cancer

Anal cancer refers to the development of abnormal cells in the tissues of the anus, which have the ability to multiply and spread.

What is anal cancer?

Anal cancer refers to the development of abnormal cells in the tissues of the anus, which have the ability to multiply and spread.

While most anal cancers are squamous cell cancers (SCC), they can also be classified as basal cell carcinoma (BCC), melanoma or adenocarcinoma of the anus.1

Anal cancer is classified as a rare cancer and is more common in New Zealanders aged over 50 years.1

Causes of anal cancer

Lifestyle, health and genetic factors that can increase your risk of developing anal cancer include:1

  • Infection with the human papilloma virus (HPV)
  • History of multiple sexual partners and receptive anal intercourse
  • Pre-existing conditions including immunodeficiency, long term inflammation around the anus, chronic fistula disease and cervical, vulval and vaginal cancers/cell abnormalities in women
  • Smoking

The most common cause of anal cancer is the sexually transmitted infection known as human papillomavirus or HPV. HPV increases the risk of many cancers, including cervical, vaginal, penile, mouth and throat cancers.2

Signs and symptoms of anal cancer

Frequent urge to defecate

Difficulty controlling bowel movements

Blood or mucus in stool

Pain, discomfort or itching around the anus

However, as these symptoms can also be caused by other common conditions, it’s important to consult a medical specialist.

Stages of anal cancer

The TNM system is used to stage anal cancer, and it helps doctors understand what your cancer looks like. TNM stands for:

  • Tumour – the degree to which the tumour has affected other tissue
  • Node – is a measure of whether lymph nodes have been affected
  • Metastasis – the degree to which the cancer has spread to other organs of the body

Treatment for anal cancer

Frequently asked questions

How common is anal cancer in New Zealand?

In New Zealand, 250 people are diagnosed with anal cancer each year. Despite being classified as a rare cancer, adults aged over 70-years-old are most commonly diagnosed with anal cancer. After age 50, anal cancer is slightly more common in women.1

How do you know if it’s anal cancer or haemorrhoids?

Haemorrhoids, or piles are soft lumps of enlarged blood vessels around and inside the anus. They usually result from a sudden increase in pressure – such as during pregnancy, constipation or heavy weight lifting.

Symptoms of haemorrhoids can include:5

  • Painful bowel motions
  • Bright red blood on toilet tissue, or in the stool
  • Extreme itching around the anal area
  • A lump or swelling around the anus

Because the symptoms of haemorrhoids and anal cancer can be similar, it is extremely important that you see your GP or healthcare professional if you are experiencing any symptoms of haemorrhoids or anal cancer so that a diagnosis can be made.

What can I do to decrease my risk of anal cancer?

There is no proven way to prevent anal cancer. However, some things that can be done to reduce your risk include:2

  • Practicing safe sex to prevent the development of HPV or HIV
  • Getting vaccinated against HPV
  • Stopping smoking
How is anal cancer diagnosed?

Tests to diagnose anal cancer include:1

  • Blood tests – checking red blood cell count, liver and kidney function
  • Examination and biopsy of the anal canal
  • MRI scan
  • Endorectal ultrasound
  • CT scan
  • FDG-PET scan


For a full list of references, click here.
  1. Bowel Cancer New Zealand. (2020). Anal cancer. Retrieved on 13 October 2020 from
  2. Mayo Clinic. (2019). Anal cancer. Retrieved on 15 January 2020 from
  3. Cancer Research UK. (2019). Anal cancer – Stages and types. Retrieved on 15 January 2020 from
  4. Cancer Council NSW. (2018). Anal cancer. Retrieved on 15 January 2020 from
  5. Healthline. (n.d). Haemorrhoids. Retrieved on 15 January 2020 from

Become a patient

Find out how to become a patient at Bowen Icon Cancer Centre or request more information from an experienced member of our team.
Become a patient

Our doctors

Our centre brings together a dedicated team of experienced medical oncologists, radiation oncologists and haematologists.
Learn more

Care team

Every member of our team are here to help you. Here are some of the people you may meet and the role they have in your care.
Learn more
View all


Contact us

  • 04 896 0200
  • Level B3, Bowen Specialist Medical Centre 98 Churchill Drive Crofton Downs Wellington 6035