Patient population and study design

Institutional Review Board approval was obtained for this prospective study, and a waiver of informed consent granted as universal testing is the standard clinical practice at our institution. Women ages 18 and older with newly diagnosed endometrial cancer undergoing surgery at The University of Texas MD Anderson Cancer Center (Houston, TX) from August 2012-August 2014 underwent tumor testing on their pathology specimens. Patient demographics were retrieved from the electronic medical record and included age at endometrial cancer diagnosis, body mass index (BMI), FIGO surgical stage, tumor histology, FIGO tumor grade (non-endometrioid tumors were considered grade 3), depth of myometrial invasion, and tumor location within the uterus (corpus vs. lower uterine segment). Data extraction was performed primarily by author ASB and validated by author KLR. Tumor testing consisted of immunohistochemistry for the expression of DNA MMR proteins MLH1, MSH2, MSH6, and PMS2, with MLH1 promoter methylation analysis in cases of IHC loss of MLH1, and PCR-based microsatellite instability (MSI) testing. Pre-analytic, analytic, and post-analytic barriers to definitively classifying an endometrial carcinoma as sporadic or Lynch syndrome related were recorded.