Anal cancer is a type of squamous cell carcinoma that arises near the squamocolumnar junction. In simpler terms, anal cancer is a type of cancer which arises from the anus, the distal orifice of the gastrointestinal tract. It is an entity of the more common colorectal cancer. Anal cancer is a type of disease in which malignant cells form in the tissues of the anus.

The anus is generally formed of different types of cells, and each type can become cancerous. The following types of anal cancer are seen based on type of cell where the cancer began:

Squamous cell carcinoma 

It is a kind of cancer that begins in the outer lining of anal canal. It is sometimes called epidermoid cancers & it is most common type of anal cancer. It has been founded that 8 out of 10 anal cancers (80%) are squamous cell cancers. Different types of squamous cell anal cancer:

  • Large cell keratinising
  • Large cell non keratinising (also called transitional)
  • Basaloid

Non epidermoid cancer

Non epidermoid cancer accounts for about one-quarter of all anal cancers. The rest of 2 out of 10 anal cancers (20%) are adenocarcinoma, small cell cancers, undifferentiated cancers, basal cell carcinoma and melanomas. This group is known as non epidermoid cancers.

The cancer which starts at the anal margin, usually look more like normal cells. Men usually suffer from anal margin tumors than women. Women are more prone to cancers that start higher up in the anal canal.


Adenocarcinoma is a rare type of anal cancer which arises from the glands that make mucous located under the anal lining. Only 5% of anal cancers are this type.

Basal cell carcinoma

Basal cell carcinoma is a type of skin cancer that develops in the perianal (around the anus) skin. The basal cell carcinoma is most often diagnosed in people in middle or old age. If a person is diagnosed with one basal cell cancer, it increases the risk of getting another.


Melanoma is also a type of skin cancer. It begins in cells that produce melanin, the pigment (color) for the skin. When someone is diagnosed with melanoma, the person has a risk of getting a second melanoma which is 9 times higher than other people in the population. The studies have shown an increased risk of melanoma in men with a higher body mass index.