ARID1B and endometrioid adenocarcinoma: The relatively high number of dedifferentiated carcinomas, almost all defined by co‐loss of ARID1B/ARID1A, highlights the importance of ARID1B assessment (in our case by IHC), which in itself represents a higher risk diagnosis than high‐grade endometrioid carcinoma in more cases than those upgraded by p53abn [12, 21].