An NRG Oncology/GOG study of molecular classification for risk prediction in endometrioid endometrial cancer.

•Molecular classification of endometrioid endometrial cancers identifies cases at increased risk for recurrence.•Women whose tumors have copy number alterations have reduced progression-free and cancer-specific survival.•~8% of endometrioid endometrial cancers are copy number altered, the majority of which are low grade, low stage cases.