Important advances during the past decade have honed on defining the cell of origin of HGSOC, identifying genomic vulnerabilities to therapies (PARPi), classifying HGSOC tumors as HR deficient or HR proficient for treatment selection, and identifying subsets of ovarian tumors with unique genomic features for which targeted treatment is still evolving, such as with cyclin E–amplified HGSOC and Arid1A-mutated clear cell ovarian carcinoma. The gene discussed is ARID1A; the disease is ovarian neoplasm.