Ampullary Flat Intraepithelial Neoplasia, High Grade

**Semantic type:** Neoplastic Process

**Definition:** A non-polypoid, preinvasive neoplasm that arises from the ampulla of Vater. It is characterized by the presence of high grade dysplasia.

**Synonyms:** - Ampullary Flat Intraepithelial Neoplasia (Dysplasia), High Grade - Flat Intraepithelial Glandular Neoplasia, High Grade