While the copy number and survival profile of our TP53m EnOC group provides one rationale for reclassification of these tumours as HGSOC, the high frequency (48.3%, 14 of 29) of classic EnOC mutations (CTNNB1, PTEN, ARID1A, KRAS, PIK3CA, or MMRm), lack of WT1 expression (in all cases) and high rate of early stage diagnosis in this cohort (51.7%, 15 stage I/II) form a compelling argument that these represent true EnOC. The gene discussed is ARID1A; the disease is neoplasm.