The type of anal cancer you have depends on the type of cell the cancer started in. Knowing the type of anal cancer you have helps your doctor decide which treatment you need.
Squamous cell cancer
This is the most common type. About 8 out of 10 anal cancers (80%) are squamous cell 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.
There are 3 types of squamous cell cancer:
- large cell keratinising which start in the lower part of the anus - the cancer cells contain keratin (the protein in your hair and nails)
- large cell non keratinising which start in the transitional zone of the anal canal - this is where the anal canal meets the rectum
Many anal cancers have a mix of these cell types. Doctors treat all these squamous cell types of anal cancer in the same way.
Non epidermoid cancer
The other 2 out of 10 anal cancers (20%) are called non epidermoid cancers. These are different from squamous cell anal cancers, so the treatment is different.
There are different types of non epidermoid cancers including:
- adenocarcinoma which develops from the glandular cells that produce mucus in the anal canal - this type is rare, and doctors treat it in the same way as rectal cancer
- basal cell carcinoma which is a type of skin cancer - it starts in the skin area around the anus
- melanoma which is another type of skin cancer starting in skin cells called melanin - doctors treat this type in the same way as melanomas
- small cell cancers
- undifferentiated cancers