Histopathological examination of the tumor. (a) Magnification, ×40. (b) Magnification, ×100. H&E staining showed that the tumor was predominantly composed of a large number of diffuse fusiform cells and myxoid matrix. The fusiform tumor cells were arranged in a multi-nodular pattern, with indistinct cell margins, slightly eosinophilic cytoplasm, and hyperchromatic atypical nuclei. Mitoses were infrequent. Many elongated curvilinear capillaries were observed.