The first PALB2 association study, which involved familial breast cancer cases and unaffected controls from the UK population, reported that the average estimated risk conferred by five PALB2 mutations is 2.3 (95% CI 1.4 to 3.9) [8] but subsequent population-based studies have estimated the risk associated with at least some PALB2 mutations to be much higher [12,13]. This evidence concerns the gene PALB2 and breast cancer.