958 Impact of the integration of the molecular classification of endometrial cancer on risk stratification of endometrial carcinomas: our institution experience, A 131 case series

Introduction/Background Endometrial cancer is the most frequent gynecological cancer in Europe. Recently, a molecular-based classification of Endometrial carcinoma (EC) has been proposed and its prognostic relevance confirmed. This classification has been incorporated into the ESGO/ESTRO/ESP guidelines for the management of patients with EC. Methodology We present a series of 131 cases of EC on which immuhistochemical stains for p53, MLH1, MSH2, MSH6 and PMS2 (clones D0–7, M1, G219–1129, 44, NB10 using Benchmark XT) and mutation analysis of POLE and TP53 (sequencing of a custom Ampliseq panel using Ion Gene Studio S5) were performed. Additional relevant pathology data was gathered. All cases were classified in prognostic risk groups according to the current ESGO/ESTRO/ESP guidelines, categorizing them both with and without the integration of molecular markers in order to study the impact of the inclusion of this information on risk stratification. Results Of the 131 cases studied, in 7 instances there was a modification in their prognostic classification due to the incorporation of molecular information. All 7 cases were Endometrioid carcinomas, 3 of them were Copy number high while the other 4 had pathogenic mutations in POLE, 2 of these were Ultramutated while the other 2 were Multiple classifiers (MCs). Of the 7 discordant cases 5 were of high histologic grade while 2 were low grade lesions. We also consider worth reporting that in the global of our series 10% of the cases were MCs. Conclusion Our series proves the feasibility of applying the molecular classification of EC in daily practice and it indicates that it is most relevant in the prognostic stratification of Endometrioid carcinomas, particularly high grade lesions, supporting the recommendation of specially studying this cases. Additionally we detected a substantially higher percentage of MCs than expected pointing to the need of a more in-depth study of the prognostic implications of this molecular group. Disclosures None.