Myxoid spindle cell sarcoma with ETV6-NTRK3 fusion.

Myxoid spindle cell sarcoma is a rare sarcoma with a demanding histopathologic diagnosis due to the absence of pathognomic immunohistochemistry markers. Genetics include complex karyotypic alterations without characteristic molecular abnormalities for this entity. NTRK alterations are rare findings with great clinical importance since they can be therapeutically targeted with two NTRK inhibitors. Herein we present a case of an adult unclassified myxoid spindle cell sarcoma with ETV6/NTRK3 fusion gene, which is a molecular finding characteristic for infantile fibrosarcoma.