MUC1 and pancreatic intraductal papillary-mucinous neoplasm: IPMN can be classified into 4 subtypes (gastric, intestinal, pancreatobiliary, and oncocytic types) based on morphological features and immunohistochemistry for mucin core proteins (MUCs).[2] MUC1 is a membrane-associated mucin that is known to contribute to epithelial cell-to-cell interactions and is predominantly expressed in the normal pancreas.