SMAD4 and exocrine pancreatic carcinoma: About half of pancreatic carcinomas contain either homozygous deletions of the SMAD4 locus or inactivating mutations in one allele associated with LOH, and a resultant loss of SMAD4 expression in pancreatic carcinoma has been documented (Hahn et al, 1996; Wilentz et al, 2000).