Given the comparable frequency of BRCA1, BRCA2 and TP53 mutations among patients diagnosed at ≤ 35 years and the high penetrance of TP53 mutations, we suggest that all patients who develop breast cancer at ≤ 35 years of age should be offered genetic counseling and a family history of LFS-linked cancers should be carefully obtained. This evidence concerns the gene TP53 and breast cancer.