When the subgroups of women with a germline BRCA1 and BRCA2 PV were analysed separately, there was a trend towards a significantly greater proportion of tumours with CRS3 in the germline BRCA2 PV subgroup compared to the germline BRCA1/2 wild type group (OR 2.13, 95% CI 0.95–4.91; P = 0.0647) (Table 4 and Fig. 3). Here, BRCA1 is linked to acquired polycythemia vera.