Fig. 1

Imaging findings at presentation. A-C Axial MRI findings of the right upper extremity. The lesion had homogeneous low intensity on T1-weighted images (A), heterogeneous high intensity on T2-weighted images (B), and heterogeneous enhancement after gadolinium administration (C). D PET/CT demonstrates FDG uptake (SUVmax: 11.3) in a spindle-shaped tumor in her right arm. Two tail-like accumulations (black arrows) were found on the central side. E, F Pathological findings. A dense array of spindle-shaped tumor cells proliferated without forming an obvious structure (hematoxylin and eosin (E), ×40; staining with MIB-1 (F), ×40)