It’s remarkable that criteria of malignancy were proposed by some authors, since SFTs are considered as intermediate malignant tumors, including histological criteria such as increased cellularity with crowded/overlapping nuclei, cellular pleomorphism, mitotic count of more than 4 per 10 high-power fields, presence of necrosis and negativity in CD-34 and Bcl-2 and clinical features as a large tumor size and an extra thoracic location. The gene discussed is CD34; the disease is neoplasm.