Types of anal cancer

The type of anal cancer you have depends on the type of cell the cancer started in. Most anal cancers start in a type of cell called squamous cells. Other rare types include adenocarcinoma and melanoma.

Squamous cell cancer

Squamous cell cancers are the most common type of anal cancer. Squamous cell carcinomas make up around 90 out of 100 (90%) of all anal cancers. They are also called epidermoid cancers.

This type of anal cancer starts in squamous cells, which make up the lining of the anal canal and anal margin. 

There are different types of squamous cell cancer. Doctors treat all these squamous cell types of anal cancer in the same way.

Your treatment also depends on the position of the cancer in your anus. Cancers that start in the anal canal might have different treatments than cancers that start in the anal margin.

Rare types of anal cancer

There are other types of anal cancer that are very rare. These make up the rest of anal cancers. The treatment of these cancers differs from the treatment for squamous cell anal cancer. 

Adenocarcinoma 

This develops from the glandular cells that produce mucus in the anal canal. It is rare, and doctors treat it in the same way as rectal cancer.

Basal cell carcinoma

This is a type of skin cancer. It starts in the skin around the anus (perianal skin).

Melanoma 

This is another type of skin cancer, it is very rare. It starts in skin cells called melanocytes. Doctors treat this type of anal cancer in the same way as melanomas.

Other types of rare anal cancers include:

• gastrointestinal stromal tumours
• poorly differentiated neuroendocrine tumours
• lymphomas