Anal cancer   

Anal cancer is a rare form of malignant tumor of the anal canal, the terminal portion of the digestive tract measuring 3 to 4 cm, located between the rectum and the skin of the anal margin. Anal cancer should not be confused with rectal cancer, another form of cancer of the gastrointestinal tract that develops from the lining of the large intestine.  

The anal canal is lined with three types of cells that line its cavity and surface (epithelia); each of which can be affected by a particular type of cancer, which explains that there are different types of anal cancers: squamous cell carcinoma, often caused by infection of the human papillomavirus type 16 and 18; cloacogenic carcinoma, a rare form of anal  cancer that presents the same symptoms and requires the same treatment as squamous cell cancer; and adenocarcinoma, an exceptional rare form of anal cancer arises from the glandular cells. Among these three, squamous cell carcinoma is the most common.  

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