Fig. 1

Histomorphological features of the tumor in this study. A The MRI imaging showed a huge soft tissue mass growing around the left scapula. B The contrast-enhanced CT showed the tumor grew inside and outside the shoulder blade, and the scapular spine. C The pre-chemotherapy biopsy showed spindle and ovoid cells that were arranged in solid sheets. D The post-chemotherapy tumor showed the primitive small round cells (yellow arrow) and larger myoid like cells (red arrow). E Crescent-shaped gaps were noted around the nests, forming a glomerular-like structure in the post-chemotherapy tumor. F Vascular stenosis and occlusion were detected in the post-chemotherapy tumor. G–L IHC staining demonstrated that BCOR, AR, and bcl2 showed diffuse and strong staining in the pre-chemotherapy biopsy (G, I, K), but focal positive mainly in myoid cells in the post-chemotherapy tumor (H, J, L). M, N IHC showed that SMA expression was negative in most tumor cells in the pre-chemotherapy biopsy (M) but positive in myoid cells in the post-chemotherapy tumor (N)