Abstract

The clinico-pathological features of 11 solitary fibrous tumors (SFT) are described. The age of the patients ranged from 19 to 70 years (average, 43 years); 6 were male patients. Ten tumors were benign and arose in the pleura (three tumors), peritoneum (two), mediastinum (two), nasal cavity (one), thymus (one), and lacrimal gland (one). One tumor was histologically malignant and arose in the pleura. All of the tumors were grossly well circumscribed. The tumors measured from 0.8 cm to 50 cm in greatest diameter. Histologically, the tumors were composed of cytologically bland spindle cells arranged without obvious pattern; focally storiform, fascicular growth patterns and hemangioperi- cytoma-like vascular patterns were seen. Tumor cells were separated by thick bands of collagen demonstrating foci of keloid-like hyalinization. Increased mitotic activity (4 mitoses in 10 high-power fields) and high cellularity with mild cytologic atypia was noted in a pleural case, suspicious of malignant tumor, Immunohistochemically, all cases tested attained positivity for vimentin, CD34, and two cases showed focal myofibroblastic differentiation. Ultrastructural study of three cases showed mesenchymal cells with fibroblastic differentiation. Follow-up for 3 to 96 months (average, 39 months) showed no tumor recurrence or metastasis. SFT are easily overdiagnosed if strict criteria are not carefully applied, and strict diagnostic criteria are necessary to avoid confusion of SFT with more aggressive lesions.

• Keywords: Solitary fibrous tumor;CD34