1008 women with high-grade ovarian carcinoma (serous, endometrioid, clear cell, carcinosarcoma) were tested for pathogenic variants (PV) in germline homologous recombination repair (HRR) genes and tumour homologous recombination deficiency (HRD) including tumour BRCA1/2 and genomic instability (GI). Over 95% of tumours with a BRCA1 PV had High GI, whilst only 80% with a BRCA2 PV and 50% with a PV in a non-BRCA HRR gene had High GI. These data suggest clinical-grade HRD assays may not detect all true HRD tumours. (By Dr Robert D Morgan, https://jmg.bmj.com/content/early/2025/08/13/jmg-2025-110903 )