Fig. 3

Sarcomatoid area of the tumor. (A) The spindle cells arrange in interlacing pattern(H&E stain, × 100); (B) The sarcomatoid cells(in the right)intermix with the typical PSP component(in the left) and metaplastic bone can be seen at the bottom of the picture (H&E stain, × 100); (C) The monomorphic tumor cells show brisk mitotic activity(yellow circles, H&E stain, × 400); The sarcomatoid spindle cells are negative for TTF-1 (D) and EMA (E), while the surrounding PSP cells are positive for both markers (× 100); (F) Ki-67 index is very high in the sarcomatoid spindle cells (× 100)