CHEK2 and breast cancer: 1–9 These studies have shown an almost equal rate of BRCA1/2 PVs to all additional potentially actionable gene PVs combined. In addition, much of the increased detection is due to variants in less actionable moderate-risk genes,10ATM and CHEK2, with higher background population prevalence. The only other actionable breast cancer gene variants consistently identified at substantial rates is PALB2, which is now also considered to be a high-risk susceptibility gene.11