CHEK2 and cancer: The spectrum of mutational signatures in CHEK2-deficient cancers resembles sporadic cancers more than what is observed in BRCA1/2-deficient cancers (Supplementary Figure 4, available online), which is also observed when we compare CHEK2-deficient cancers with cancers with heterozygous gPV in BRCA1/2, for which it was not clear if a somatic second hit was present (n = 134 cancers).