From a histological point of view, the differential diagnosis includes NTRK-rearranged spindle cell neoplasms (see below), dermatofibrosarcoma protuberans (DFSP, see Section 2.6), desmoid fibromatosis, synovial sarcoma (see Section 7.3), the exceptional EWSR1-SMAD3 positive fibroblastic tumor (see Section 2.4) and ALK-rearranged infantile fibrosarcoma-like tumor (see Section 2.5). The gene discussed is SMAD3; the disease is neoplasm.