Prospective molecular classification of endometrial carcinomas: institutional implementation, practice, and clinical experience

The comprehensive genomic analysis of endometrial carcinoma (EC) by The Cancer Genome Atlas (TCGA) led to the discovery of four distinct and prognostically significant molecular subgroups. Molecular classification has the potential to improve risk-stratification when integrated with clinicopathologic features and has recently been included in national and international patient management EC guidelines. Thus, the adoption of molecular classification into routine pathologic and clinical practice is likely to grow significantly in the upcoming years. Establishing an efficient and standardized workflow for performing molecular classification on ECs, and reporting both the molecular and histologic findings in an integrative manner, is imperative. Here we describe our effort to implement rapid and routine molecular classification on all ECs diagnosed at our institution. To this effect, we performed immunohistochemistry as a surrogate marker for identifying genetic and/or epigenetic alterations in DNA mismatch repair (e.g., MLH1, PMS2, MSH6, MSH2), and TP53 genes. In addition, we have developed and employed a single-gene POLE SNaPshot assay, which is a rapid and analytically sensitive method for detecting select POLE exonuclease domain mutations (EDMs). We report our molecular testing workflow and integrative reporting system as well as the clinicopathologic and molecular features of 310 ECs that underwent routine molecular classification at our institution. The 310 ECs were molecularly classified as follows: 15 (5%) POLE mutant (POLEmut), 79 (25%) mismatch repair-deficient (MMRd), 135 (44%) no specific molecular profile (NSMP), and 81 (26%) p53 abnormal (p53abnl). This work provides an initial framework for implementing routine molecular classification of ECs.