These guidelines define the primary and secondary prevention, especially in previously oncologically healthy individuals at high risk of cancer caused by germline mutations in the highly and moderately penetrant cancer predisposition genes BRCA1, BRCA2, PALB2, ATM a CHEK2, which occur most frequently in breast, and ovarian cancers, prostate, pancreas, but also other organs [65]. The gene discussed is CHEK2; the disease is cancer.