A 50 year old lady presented with a 3-months history of pain in the lower third of the right thigh.There was no local swelling; tenderness was present on deep pressure.Plain X-ray showed an ill-defined intra medullary lesion with blotchy calcification at the lower end of the right femoral diaphysis, possibly enchondroma or chondrosarcoma. Sections showed a cartilaginous tumor.Which of the following histological features(if seen) would be most helpful to differentiate the two tumours ?

• A. Tumor permeation between bone trabeclae at periphery
• B. Focal necrosis and lobulation
• C. High cellularity
• D. Extensive myxoid change