They report a similar prevalence of ARID1A loss to published studies, with loss of ARID1A staining observed in 25% of ENOC and 42% of CCOCs, with retention of ARID1A protein in more than 95% of both low‐grade (n = 111) and high‐grade serous ovarian cancer cases (n = 2,548). Here, ARID1A is linked to ovarian serous adenocarcinoma.