Paraffin-embedded sections stained with hematoxylin and eosin showed a moderately cellular, densely collagenous neoplasm composed of fusiform cells with oval-to-elongated nuclei, delicate, evenly distributed chromatin, and indistinct nucleoli. Spindle shaped tumor cells were arranged in delicately interconnected, intertwining networks, and individual cells were separated from one another by swirls of dense collagen, which frequently encircled vascular lumina. There was mild, focal cellular pleomorphism. Calcification, vascular hyalinization, necrosis, mitotic figures, or a distinct capsule were not identified. No cytoplasmic aggregates were seen in PAS stained sections. A Trichrome stain confirmed the presence of abundant collagen. Immunohistochemical stains for EMA, S100, factor VIII-related-antigen, actin, desmin, progesterone and estrogen receptors were negative, but the tumor cells were strongly positive with stains for CD34 and vimentin.