Accordingly, Apc+/1572T/Smad4+/Sad compound heterozygous mice revealed a similar incidence of mammary adenocarcinomas as in Apc+/1572T, but were also characterized by multiple GI-tract tumors never observed in the parental strain, even when kept for longer than 1 year. This evidence concerns the gene SMAD4 and breast adenocarcinoma.