TP53 and breast cancer: 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.