OBJECTIVE: To evaluate whether the amount of preoperative endometrial tissue surface is related to the degree of concordance with final low- and high-grade endometrial cancer (EC). In addition, to determine whether discordance is influenced by sampling method and impacts outcome. METHODS: A retrospective cohort study within the European Network for Individualized Treatment of Endometrial Cancer (ENITEC). Surface of preoperative endometrial tissue samples was digitally calculated using ImageJ. Tumor samples were classified into low-grade (grade 1-2 endometrioid EC (EEC)) and high-grade (grade 3 EEC + non-endometroid EC). RESULTS: The study cohort included 573 tumor samples. Overall concordance between pre- and postoperative diagnosis was 60.0%, and 88.8% when classified into low- and high-grade EC. Upgrading (preoperative low-grade, postoperative high-grade EC) was found in 7.8% and downgrading (preoperative high-grade, postoperative low-grade EC) in 26.7%. The median endometrial tissue surface was significantly lower in concordant diagnoses when compared to discordant diagnoses, respectively 18.7 mm2 and 23.5 mm2 (P = 0.022). Sampling method did not influence the concordance in tumor classification. Patients with preoperative high-grade and postoperative low-grade showed significant lower DSS compared to patients with concordant low-grade EC (P = 0.039). CONCLUSION: The amount of preoperative endometrial tissue surface was inversely related to the degree of concordance with final tumor low- and high-grade. Obtaining higher amount of preoperative endometrial tissue surface does not increase the concordance between pre- and postoperative low- and high-grade diagnosis in EC. Awareness of clinically relevant down- and upgrading is crucial to reduce subsequent over- or undertreatment with impact on outcome.

Biomedical Research Group in Gynaecology Vall d'Hebron Institute of Research Universitat Autònoma de Barcelona CIBERONC Barcelona Spain

Department of Gynaecology and Obstetrics University Hospital Brno Faculty of Medicine Masaryk University Brno Czech Republic

Department of Obstetrics and Gynaecology Canisius Wilhelmina Hospital Nijmegen the Netherlands

Department of Obstetrics and Gynaecology Hosepital del Mar PSMAR Barcelona Spain

Department of Obstetrics and Gynaecology Radboud university medical center Nijmegen the Netherlands

Department of Obstetrics and Gynaecology Radboud university medical center Nijmegen the Netherlands; Department of Obstetrics and Gynaecology Canisius Wilhelmina Hospital Nijmegen the Netherlands

Department of Oncology KU Leuven Leuven Belgium; Department of Gynaecological Oncology Amsterdam Netherlands Cancer Institute Amsterdam the Netherlands

Department of Pathology and Molecular Genetics and Research Laboratory Hospital Universitari Arnau de Vilanova University of Lleida IRBLleida CIBERONC Lleida Spain

Department of Pathology Canisius Wilhelmina Hospital Nijmegen the Netherlands

Department of Pathology Ghent University Hospital Cancer Research Institute Ghent Ghent Belgium

Department of Pathology Radboud University Medical Centre Nijmegen the Netherlands

Department of Pathology University of Turku Turku Finland

Department of Radiation Oncology Radboud university medical center Nijmegen the Netherlands

Gynaecological Department Vall d'Hebron University Hospital CIBERONC Barcelona Spain; Pathology Department Vall d'Hebron University Hospital CIBERONC Barcelona Spain

Institute of Pathology University Hospital Brno Faculty of Medicine Masaryk University Brno Czech Republic

Obstetrics and Gynaecology Department Bichat Claude Bernard Hospital Paris France

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