Solution: Main duct Intraductal Papillary Mucinous Neoplasm (IPMN) is a neoplasm of the pancreas that can be benign or malignant. Side-branch IPMN's are being more frequently seen and recognized. These generally have a more benign course, but main duct IPMN's are more concerning because they have a higher likelihood of malignancy and because of the mucous production, they can be symptomatic, causing pancreatitis. The diagnosis is generally confirmed with ERCP, identifying the characteristic "Fish-eye" appearance of the ampulla (mucous bulging out of the ampulla) and the mobile, compliant mucous filling the duct. Differentiating benign from malignant disease is difficult, and there have been numerous papers written about the subject. From an imaging standpoint, the main things to look for are: Duct wall enhancement, mural nodules that show enhancement, duct enlargement >1.5 cm, abnormal attenuation or signal in the pancreatic parenchyma. Any one of these makes the patient at higher risk for malignancy. In the end, most of these are surgically resected and the determination is made at histopathology.