Rather than the standard distribution, the non-TCGA subset of ExAC is used because as a large collection of cancer samples, TCGA is likely to be enriched for mutations related to cancer predisposition; for example, germline pathogenic mutations were previously detected in TCGA ovarian cancer samples for BRCA1, BRCA2, and PALB2 (Kanchi et al. 2014). This evidence concerns the gene PALB2 and ovarian cancer.