Rare mutations of other tumor suppressor genes involved in direct protein-protein interaction with BRCA1/2 including TP53, PTEN, CHEK2, ATM, NBS1, RAD50, BRIP1, and PALB2 were also discovered in breast cancer families, altogether accounting for up to 50% of familial breast cancers [2,3]. Here, CHEK2 is linked to breast carcinoma.