CHEK2 and breast cancer: Of the five double heterozygotes involving CHEK2 with ATM, PALB2, RAD50, or MUTYH in our study, we noted a younger age of BC presentation than the cohort median in three cases (CHEK2 c.433delC/MUTYH c.536A > G, age 34; CHEK2 c.1100delC/PALB2 c.2827_2830del, age 25; CHEK2 c.1100delC/ATM c.237del, age 29), and bilateral and multifocal tumors in only one patient (CHEK2 c.707 T > C/RAD50 c.2517dupA).