Figure 3: (a) Case of mesenchymal chondrosarcoma showing undifferentiated mesenchymal cells with uniform round blue cells admixed with areas of chondroid differentiation (hematoxylin and eosin 200×); (b) diffuse positive expression for CD99; (c) positive expression for NKX2.2 (moderate intensity); and (d) FISH (break-apart) analysis negative for EWSR1 gene rearrangement