Homozygous deletion or intragenic inactivating mutations of SMAD4, also named DPC4 for Deleted in Pancreatic Cancer locus 4, as well as the complete loss of Smad4 protein expression, are observed in 50% ductal adenocarcinomas, 34% of invasive adenocarcinomas of the Vater ampulla and 55% endocrine pancreatic carcinomas [40]. The gene discussed is SMAD4; the disease is invasive ductal breast carcinoma.