Heterozygous carriers of pathogenic variants (principally protein truncating variants, PTVs) in ATM have been shown in multiple studies to be associated with a moderately increased risk of breast cancer (BC), with a relative risk (RR) of approximately 2.2 3 Recent studies have also shown clear associations between ATM PTVs and a wide range of other cancer types, notably prostate,4 5 gastric, pancreatic,5 6 colorectal,7 lung, bladder, ovarian and oesophageal cancer, diffuse non-Hodgkin’s lymphoma, lymphoid leukaemia, and melanoma.5 Here, ATM is linked to breast cancer.