Incidence of Anal Cancer

human papillomavirus (hpv) is the most prevalent sexually transmitted infection. It is more common than herpes and chlamydia and it has been estimated that more than 75% of sexually active adolescents and adults between the ages of 15 and 49 will acquire at least one type of hpv infection. The infection is practically guaranteed in people with more than five sex partners in their lifetime. More than 100 different hpv genotypes exist, approximately 10 to 15 of which are known to cause disease in genital mucosal tissues. These include nononcogenic varieties—primarily types 6 and 11, as well as types 42, 43, and 44—associated with the development of genital condylomas or mild dysplasia and generally do not progress to either higher-grade lesions or cancer. Oncogenic varieties—types 16 and 18, in particular— are associated with more dysplastic lesions and account for the majority of invasive cervical or anal carcinoma cases. Types 31, 33, and 35 are associated with an intermediate risk of high-grade dysplasia and cancer.