A gastrointestinal tract sarcoma with neuroectodermal differentiation. It is characterized by the presence of neoplastic round cells with pale eosinophilic cytoplasm. Cytoplasmic clearing is seen only in a minority of cases. Half of the cases contain osteoclastic giant cells. It is associated with gene fusion translocations involving the EWSR1 gene, usually EWSR1-ATF1 fusion or EWSR1-CREB1 fusion. [from
NCI]