What is anal cancer?

Anal cancer is cancer affecting the tissues of the anus. Cancer is a disease of the cells. Cells are the body’s basic building blocks – they make up tissues and  organs. The body constantly makes new cells to help us grow, replace worn-out tissue and heal injuries.

Normally, cells multiply and die in an orderly way, so that each new cell replaces one lost. Sometimes cells become abnormal and keep growing. These abnormal cells may form a lump called a tumour.

If the cells in a tumour are cancerous, they can spread through the bloodstream or lymph vessels and form another tumour at a new site. This new tumour is known as secondary cancer or metastasis.

Types of anal cancer

Squamous cell carcinoma (SCC) – Most anal cancers are SCCs. These start in the flat (squamous) cells lining much of the anus. The term “anal cancer” commonly refers to SCCs, and this website information focuses on this type of anal cancer.

Adenocarcinoma – Some anal cancers are adenocarcinomas. These start in cells in the anal glands. This type of anal cancer is treated in a similar way to bowel cancer.

Skin cancer – In rare cases, SCCs can affect the skin just outside the anus. These are called perianal skin cancers. If they are not too close to the sphincter muscles, they can be treated in a similar way to SCCs on other areas of the skin. For more information, see Skin Cancer.

How common is anal cancer?

Every year, about 460 people are diagnosed with anal cancer in Australia. It is more common over the age of 50 and is slightly more common in women than in men. The number of people diagnosed with anal cancer has increased over recent decades.