Pancreatic intraepithelial neoplasia, intraductal pancreatic mucinous neoplasm (IPMN), and mucinous cystic neoplasm (MCN) are the common precursor lesions of pancreatic cancer. The gene abnormalities of those precursor lesions are characterized by Kras mutation and mucin overexpression.1,2 Arid1a is a subunit of the SWI/SNF complex, which serves as a tumor suppressor gene commonly absent in subsets of pancreatic cancer and IPMN patients, and low expression of Arid1a is associated with poor overall survival of pancreatic cancer.