Grade 1 Endometrioid Carcinoma With an Area of Serous Carcinoma Less than 5% Is More Aggressive than Stage IA Pure-type Grade 1 Endometrioid Carcinoma.

BACKGROUND/AIM In 2020, the percentages were removed from the World Health Organization's criteria for mixed carcinoma. The aim was to examine the clinical significance of an area of serous carcinoma (SC) <5%. PATIENTS AND METHODS Our study included 236 patients with the 2009 International Federation of Obstetrics and Gynecology (FIGO) stage IA grade 1 endometrioid carcinoma (EG1) from multiple hospitals. EG1 patients with an area of SC <5% and those with pure-type EG1 were retrospectively compared. RESULTS In the multivariate analysis for recurrence, an area of SC <5% was an independent risk factor [hazard ratio (HR)=101.51, p<0.01]. In the multivariate analysis for progression-free survival, an area of SC <5% was identified as a negative prognostic factor (HR=62.43, p<0.01). CONCLUSION EG1 with an area of SC <5% may be more aggressive than pure-type EG1 at FIGO stage IA.