CHEK2 and breast neoplasm: Using TCGA breast tumor data, we compared mutation frequencies of ERCC6 and ERCC8 to those of breast cancer susceptibility genes with high-penetrance (BRCA1, BRCA2, TP53, PTEN, CDH1 and STK11), medium-penetrance (BLM, ATM, CHEK2, BRIP1, and PALB2), and low-penetrance (FGFR2, MAP3K1, CASP8, TOX3, and LSP1), and to the rest of the genome.