Human papillomavirus and anal neoplasia.

Anal cancer is a rare disease in the general population, but the incidence of anal cancer is higher in certain at-risk groups, such as men who have sex with men (MSM), and immunosuppressed individuals, including those with HIV infection. Among HIV-positive MSM, the incidence of anal cancer may be as high as 10 times greater than current rates of cervical cancer in the general population of women. Anal cancer is associated with human papillomavirus (HPV) infection and may be preceded by high-grade anal intraepithelial neoplasia (HGAIN). HGAIN and anal HPV infection are both highly prevalent in groups at risk for anal cancer. Current issues include determining the effect of antiretroviral therapy on the natural history of HGAIN and the incidence of anal cancer, optimizing diagnostic and therapeutic approaches to HGAIN, and determining the potential for prophylactic HPV vaccines to prevent anal HPV infection and anal cancer in at-risk groups.