Molecular classification of endometrial carcinoma: a clinically oriented review

The Cancer Genome Atlas research network performed a genome-wide analysis of endometrial carcinomas in 2013 and classified tumours into four distinct subgroups: polymerase-ϵ ultramutated, microsatellite unstable hypermutated, copy-number low and copy-number high. These molecular alterations are mostly mutually exclusive as only about 3% of tumours exhibit more than one molecular signature. Apart from the polymerase-ϵ ultramutated subgroup, molecular classification can be reproduced by using surrogate markers. This has facilitated the implementation of molecular diagnostics into routine patient care. Molecular subgroups are associated with different prognoses; thus, improved risk assessment is their most obvious clinical application. However, based on their unique molecular architectures, molecular subgroups should not be regarded simply as risk groups but rather as distinct diseases. This has prompted us and others to examine the role of molecular subgroups in modifying the prognostic effect of traditional risk factors, including clinical factors, uterine factors and tissue biomarkers, and in predicting the response to adjuvant therapies. In the following review, we summarise the current knowledge of molecularly classified endometrial carcinoma and present, based on our own experience, a proposal for implementing molecular classification into daily practice in pathology laboratories.