A 45 yrs male presented with an expansile lesion in the centre of femoral metaphysis. The lesion shows endosteal scalloping & punctuate calcifications. Most likely diagnosis is -

CHONDROSARCOMA TYPES * Primary chondrosarcoma * Secondary chondrosarcoma * Periosteal chondrosarcoma * Dedifferentiated chonrosarcoma * Clear cell chondrosarcoma * Mesnchymal chondrosarcoma Primary chondrosarcoma * Malignant cailage tumour arising in previously normal bone * a/k/a central or conventional chondrosarcoma * 90% of all chondrosarcoma * Age group- 40 to 60 yrs * Male: female = 3:2 Differenciating encondroma from chondrosrcoma Enchondroma and low grade chondrosarcoma may appear radiologically similar Similarity- both located in metaphysis with stippled calcification and endosteal scalloping Histology-- similar in enchondroma and low grade chondrosarcoma ref : maheswari 9th ed