Anal Intraepithelial Neoplasia

Abstract

Anal intraepithelial neoplasia (AIN) is a histologic diagnosis characterized by malignant transformation of the anal canal without invasion below the basement membrane. AIN was first described by C. Fenger et al. in 1986. AIN affects individuals who have multiple sexual partners and a prior exposure to a sexually transmitted diseases; it also has a very strong correlation with the human papilloma virus and a high prevalence in the immunosuppressed, especially individuals with human immunodeficiency virus/acquired immune deficiency syndrome. Low-grade AIN appears to be much more common than the incidence of squamous cell carcinoma (SCC) of the anus. High-grade AIN appears to be a more worrisome lesion. Similar to patients with low-grade AIN, those with high-grade AIN should be examined for SCC in the other areas of the perineum that occur in high risk population. Extensive resections have necessitated ostomy formation and patients with premalignant lesions who are trying to avoid ostomy formation for invasive SCC through chemoradiotherapy are being diverted.