The molecular analyses of PDAC have revealed that four driver genes—KRAS, CDKN2A, p53, and SMAD4 (SMAD family member 4)—are mutated in more than 50% of cases, with KRAS being an early mutational event found in more than 95% of invasive ductal adenocarcinomas [82,83,84]. This evidence concerns the gene SMAD4 and invasive ductal breast carcinoma.