An association between MpBC and BRCA1 has previously been suggested in case report form20,21,22,23,24,25 and in 2 small series.26,45 Rodríguez-Fernández et al45 evaluated the histology of 93 patients with breast cancer and known germline variants in BRCA1 or BRCA2; 3.2% of known affected carriers had metaplastic carcinoma compared with 0.8% (25 of 3157) of a genetically unselected reference population. Here, BRCA1 is linked to breast cancer.