Pleural solitary fibrous tumor is a rare and slow growing intrathoracic neoplasm. It originates from submesenchymal cells of parietal or, more commonly, visceral pleura. Although most cases follow a benign clinical course, it has been reported that a malignant outcome is seen in 7,5-37% of cases. We present here a case considered as pleural solitary fibrous tumor with malignant potential. A 74-yearold woman presented with dyspnea and computerized tomography showed a mediastinal mass connected to the pleura. The tumor was removed by surgery. Grossly, the tumor was lobulated, welldemarcated and mostly encapsulated. Its weight was 754 gr. and it measured 17x12x5.5 cm. The cut surface had a whorled appearance. Focal necrosis and myxoid degenerative areas were noted. Histopathologically, hypocellular areas characterized by uniform, small spindle cells in a collagen rich stroma and hypercellular areas were seen. The tumor had a prominent branching vascular network. Although mitosis was infrequent, necrosis was common. Tumoral cells were strongly immunoreactive for CD34, bcl-2 and vimentin by immunohistochemistry. Cytokeratin, actin, S100, CD117 and desmin were negative. The ratio of Ki-67 positive cells was 10%. The patient was diagnosed as pleural solitary fibrous tumor with malignant potential because of hypercellularity and presence of large necrotic areas although increased mitosis and pleomorphism were almost absent. There was no recurrence or metastasis 15 months after the surgery.