Ewing sarcoma and the new emerging Ewing-like sarcomas: (CIC and BCOR-rearranged-sarcomas). A systematic review

Ewing-like sarcomas (ELS) are a heterogenous group of tumors that frequently affect pediatric and young adult patients. Accurate classification and distinction from the Ewing sarcoma family of tumor (ESFT) is decisive in patient management. ELS share a significant morphologic, immunohistochemical and clinical overlap with ESFT, thus the differential diagnosis is challenging, especially with atypical ESFT and tumors with unusual immunoprofiles or uncommon clinicoradiological findings. A subset of ELS harboring the CIC-DUX4 or BCOR-CCNB3 fusions has been described recently. The spectrum of ELS is now expanding, and additional gene fusion partners besides DUX4 or CCNB3 have been detected, and the terms CIC or BCOR-rearranged sarcomas have recently been proposed. We review the clinical, histological, phenotypic and molecular findings of ESFT and these new emerging ELS.