Figure 2

Gross observation, morphologic features and immunohistochemistry. a Gross specimen showed the tumor was solid, irregular lobular, the boundary was clear, with two small nodules next the largest one, some part of the tumor connected with the bone. The cut surface was pale yellow, with medium texture. b to e Hymatoxylin and eosin stain showed the morphologic features of the neoplastic cells. Histological examination of the resection specimen revealed that the greatest portion of the tumour was composed of interlacing bundles of elongated cells with spindle-shaped nuclei (2b). Some tumor tissues located in the bone (2c). Focal area accompanied with bleeding and degeneration (2d). The nuclei were corrugated, atypia was not obvious, enlarged and pleomorphic nuclei could be seen in some region, mitotic figure could be found occasionally (2e, black arrow). (Magnification: 2b and 2e, ×400; 2c and 2d, ×100). f Positive IHC signals were visualized with brown yellow color. Cytoplasmic and nuclear immunostaining of neoplastic cells with S-100 protein (Magnification, ×400).