IPMN : Grading
Based on the degree of cytologic and architectural atypia, intraductal papillary mucinous neoplasms (IPMNs) of pancreas are classified in a two-tiered system into low-grade and high-grade. Low-grade IPMN: The lining epithelium has flat or papillary architecture, minimal cytologic atypia and little to no mitotic activity. The nuclei are basally-oriented and there is abundant apical mucin. Low-grade IPMN includes the previous categories of IPMN with low-grade and intermediate-grade dysplasia. IPMNs lined by gastric foveolar-type epithelium are usually low-grade (shown here). High-grade IPMN It shows more complex papillary architecture, severe cytologic atypia, nuclear stratification, prominent nucleoli, loss of polarity, and increased mitotic activity. It includes the previous category of IPMN with high-grade dysplasia. Intestinal and pancreatobiliary IPMNs are frequently high-grade.