Given the importance of an accurate diagnosis for targeted therapy with poly ADP ribose polymerase (PARP) inhibitors in high-grade serous carcinomas, predictive testing for both histotypes (BRCA1/2 mutation status for HGSC and mismatch repair for EC) might be performed in rare high-grade cases that cannot be reliably classified. The gene discussed is BRCA1; the disease is serous adenocarcinoma.