Perianal Intraepithelial Neoplasia

**Semantic type:** Neoplastic Process

**Definition:** 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.

**Synonyms:** - Anal Margin Bowen Disease - Anal Margin Bowen's Disease - Anal Margin Intraepithelial Neoplasia - Anal Margin Squamous Dysplasia - Bowen Disease - PSIN - Perianal Skin Bowen Disease - Perianal Skin Bowen's Disease - Perianal Squamous Dysplasia - Perianal Squamous Intraepithelial Neoplasia