A 64-year-old man presents with forearm swelling. A gadolinium-enhanced MRI of his forearm is shown in Figure A and a CT scan of his chest is shown in Figure B. The lesion is resected and its gross and cellular histological appearance is shown in Figure C and D respectively. Fluorescence-in-situ-hybridization is negative for t(X:18) and t(12:16). Immunohistochemistry is negative for desmin, myogenin and CD34. What is the most likely pathologic diagnosis?