Tumour histology and osteoclast involvement. a) Pleomorphic, ovoid cells (*) with an additional spindle cell population (arrows) were noted for JJ012 tumours. b) Dedifferentiated chondrosarcoma from a human de novo tumour demonstrated some similar ovoid cells without a spindle cell component. c) In periosteal and intratibial tumours, TRAP staining (arrows) revealed prominent osteoclasts at the interface between tumour (T) and bone cortex (C), and this was associated with bone matrix erosion and a mass of dead cellular material (D). d) An osteoclastogenesis assay demonstrated higher osteoclasts formed by JJ012 media (CM) compared with FS090 media (CM) (* p < 0.05), and the same relationship for chondrosarcoma and mouse monocyte (RAW 246.7) co-culture (* p < 0.05).