label: Perianal Intraepithelial Neoplasia
label_lc: perianal intraepithelial neoplasia
description: A precancerous neoplastic intraepithelial process involving the squamous epithelium of the perianal skin. Clinically, it usually presents as a white or red area in the perianal skin. Morphologically, it is characterized by full thickness dysplasia of the squamous epithelium and sometimes of the pilosebaceous epithelium. Human papillomavirus DNA sometimes may be identified in the dysplastic epithelium. It may recur after treatment, however only a small percentage of cases progress to squamous cell carcinoma.