MKI67 and solitary fibrous tumor: Although CD34 is a useful marker in diagnosis of SFT, 1 should bear in mind that its expression can be lost in high-grade tumours, in addition, overexpression of p53 and Ki-67 suggests the possibility of a malignant SFT, which relates to de novo or malignant transformation within a benign or low-grade.4 England et al3 considered neoplasms to be malignant if 1 or more of the following histologic features are present: (1) high cellularity, (2) high mitotic activity (>4 mitoses per 10 high-power fields), (3) pleomorphism, (4) necrosis, and (5) hemorrhagic changes.