Human papillomavirus and anal intraepithelial neoplasia

A review of recent developments in the understanding of the natural history of anal squamous carcinoma arising from areas of high-grade anal intraepithelial neoplasia.

Anal intraepithelial neoplasia is a consequence of chronic human papillomavirus infection in the anal canal and appears to be driven by high viral loads of human papillomavirus. In men who have sex with men with multiple sexual partners prevalent human papillomavirus infection does not decline with age, in contrast to heterosexual patients. Anal intraepithelial neoplasia is equally prevalent in different age groups of men who have sex with men, but in other respects what is known of its natural history resembles that of cervical intraepithelial neoplasia. Low-grade lesions frequently resolve, but high-grade lesions are much more stable. HIV-positives who practise receptive anal intercourse are at highest risk of anal intraepithelial neoplasia. Screening is easy to perform using cytology; the limitations of anal cytology being similar to those of cervical cytology. Patients with any grade of cytological abnormality require further investigation, ideally with high-resolution anoscopy, every 6 months. Successful treatments for individual small to medium-sized high-grade lesions include trichloroacetic acid, infra-red coagulation and laser. In HIV-positive patients the development of new lesions elsewhere is very likely. Topical agents for multifocal disease include imiquimod and cidofovir.

There is a need for large prospective cohort studies in men who have sex with men and HIV-positive patients to further our understanding of this disease and to evaluate treatment strategies.