Figure 3.

Photomicrographs. A, Proliferation of spindle cells arranging in a patternless architecture (×200 original magnification). B, Alternating hypercellular and hypocellular areas of spindle cells separated from each other by bands of collagen fiber (×200 original magnification). C, Spindle cells forming haphazard, storiform, or short fascicular arrangements in a loose myxoid to fibrous stroma containing dense collagen fibers (×200 original magnification). D, Hemangiopericytoma-like staghorn-like vessels (×200 original magnification). E, Tumor cells displaying mild to moderate atypia and 3 mitoses in this high power field (arrow and arrowhead) (×400 original magnification). Abnormal mitoses were occasionally seen (inset, ×400 original magnification). F, Prominent tumor necrosis (× 400 original magnification).