Updated publication reference for PubMed record(s): 30979743. Precision medicine approaches in ovarian cancer require the accurate diagnosis of histotypes. In particular, there is a critical need to distinguish endometroid (EC) from high grade serous (HGSC) carcinomas, which differ greatly in outcomes, genetic predisposition and optimal treatment approaches. Herein, we performed label-free quantitative proteomics on freshly frozen tumour tissues to discover biomarkers that may distinguish EC from HGSC, and then used IHC to validate these using a contemporarily classified cohort of EC and HGSC samples.