Anal cancer is a broad term used to describe any type of cancer within or near the anus. Because multiple types of cells are naturally found here, several different cancer types may be classified as anal cancer. These can include Squamous cell carcinoma (the most common type), Cloacogenic carcinoma, Adenocarcinoma, Basal cell carcinoma, and Melanoma. The Human Papillomavirus (HPV) is the most frequent cause, accounting for over 90% of anal cancers. Fortunately, a vaccine is available to protect against HPV and is the primary prevention method. Roughly 8,300 adults in the United States are diagnosed with anal cancer each year.