CDKN2A and pancreatic ductal adenocarcinoma: The most important genetic events in pancreatic ductal adenocarcinoma (PDAC), the most common type of PCA, are the activation of the oncogene KRAS and the inactivation of the tumour suppressor genes cyclin dependent kinase inhibitor 2A (CDKN2A), tumour protein p53 (TP53), and SMAD4 [8,9,10,11,12,13].