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 cells 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 3 types of squamous cell cancer. Many anal cancers have a mix of all 3 cell types. 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 treatment to cancers that start in the anal margin.

Other types of anal cancer

Anal cancers that don't start in squamous cells are called non epidermoid cancers. These make up the rest of anal cancers. The treatment for non epidermoid cancer is different from the treatment for squamous cell anal cancer. 

There are different types of non epidermoid cancers, which are listed below. 

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 area around the anus.

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 non epidermoid cancer include:

• small cell cancers
• undifferentiated cancers
• lymphoma's