Both subtypes of serous ovarian carcinoma, a mesonephric adenocarcinoma case and the small cell carcinomas of the ovary, hypercalcaemic type, were ARID1A wild‐type and showed high protein expression (with scores ranging between 11 and 12 (EPR13501), 11 and 12 (D2A8U) and 6 and 12 (HPA005456) (Figure 4). Here, ARID1A is linked to ovarian small cell carcinoma.