Our analysis did not detect coding variants in the MH2 domain of SMAD3. In SMAD4 we identified two novel coding variants c.1350G > A (p.Gln450Gln) (P9), and c.1701A > G (p.Ile525Val) (C24) in a breast cancer case and control population, respectively, in addition to the previously known c.1214T > C (Phe362Phe) (rs1801250). Here, SMAD3 is linked to breast cancer.