In PDAC, a loss of SMAD4 expression has been associated with tumor size, peripancreatic extension, TNM staging, lymphatic invasion, nodal involvement and poor differentiation [51,52,53], influencing OS [54,55,56,57,58,59,60,61,62,63,64] and DFS [56,59,61,64]. This evidence concerns the gene SMAD4 and neoplasm.