Deleterious variants in XRCC3, a RAD51 paralog involved in HR, have been detected in breast and ovarian cancer at a low frequency (0.2%)43 and have recently been reported to be mutually exclusive with BRCA1 and BRCA2 mutations when analysing data from ovarian, breast, pancreatic and prostate tumours44. Here, BRCA1 is linked to ovarian cancer.