New developments in endometrial stromal sarcoma

Endometrial stromal tumours have been recently reclassified in the WHO 2014 Classification due to the discovery of new genetic fusions. This has enabled the subdivision of previously described undifferentiated endometrial sarcomas into the molecularly-defined high grade endometrial stromal sarcoma (HG ESS) and undifferentiated uterine sarcoma (UUS). In this review, we discuss the discoveries behind the 2014 Classification and its rationale, and give practical tips for diagnosis of these neoplasms, as well as discussing the differential diagnoses that one may consider.