Round cell sarcoma with CIC-DUX4 gene fusion: Discussion of the distinctive cytomorphologic, immunohistochemical, and molecular features in the differential diagnosis of round cell tumors..     ///    "Although a subset defined by recurrent CIC-DUX4 gene fusion has been recently characterized, data regarding the cytomorphologic features are currently limited. "    ///    CIC-DUX4 round cell sarcoma differs from Ewing sarcoma in that it has more atypical cytologic features and lacks the diffuse membranous CD99 staining pattern characteristic of Ewing sarcoma.     ///    "Focal-to-multifocal CD99 immunoreactivity and diffuse nuclear WT1 positivity is characteristic of CIC-DUX4 sarcoma, and should prompt molecular testing. "    ///    Fluorescence in situ hybridization demonstrated CIC-DUX4 fusion in both cases. 