Morphological assessment was included for 60 young onset cases with a germline BRCA1 pathogenic variant (group 3), 61 young onset cases with a germline BRCA2 pathogenic variant (group 4) and 98 young onset breast cancer cases (group 5) with no identifiable germline high risk pathogenic variant (BRCA1, BRCA2 or TP53) 21. Here, BRCA1 is linked to breast cancer.