Anal Canal Intraepithelial Neoplasia

**Semantic type:** Neoplastic Process

**Definition:** A precancerous neoplastic intraepithelial process involving the anal canal. When it is clinically noticeable, it may appear as an eczematous or papillary lesion, plaques, or papules. Morphologically, it is characterized by loss of epithelial stratification and nuclear polarity, cytologic atypia, and the presence of mitotic figures. It may be classified as low or high grade.

**Synonyms:** - ACIN - ASIN - Anal Canal Dysplasia - Anal Canal Squamous Dysplasia - Anal Canal Squamous Intraepithelial Neoplasia - Anal Squamous Intraepithelial Neoplasia