RESUMEN
We experienced five cases of solitary fibrous tumor; two in the pleura, two in the orbital soft tissue, and one in the lung parenchyma. Three patients were male, and the age of the patients ranged from 38 to 71 years (mean age: 53.6). Grossly, the masses were well circumscribed and had varying sizes from 2.5 to 30.0 cm. The cut surfaces were grayish-yellow firm with focal variegated hemorrhage, necrosis, cystic change, and myxoid area. Microscopically, these were characterized by a haphazard proliferation of spindle cells or polygonal cells separated by variable amounts of hyalinized collagen and showed a prominent vascular channels reminiscent of hemangiopericytoma in foci. Immunoperoxidase stains showed a strong reactivity for CD34, and were weakly positive for vimentin. Electron microscopical examination revealed features of fibroblast; spindle to round tumor cells were arranged in groups and surrounded by collagen. Nucleoli were seldom prominent. The cytoplasm contained many microfilaments and a moderate number of cisternae of rough endoplasmic reticulum.