A 50 year old lady presented with a 3-month history of pain in the lower third of the right thigh. There was no local swelling; tenderness was present on deep pressure. Plain X-rays 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) Focal necrosis and lobulation
b) Tumor permeation between bone trabeclae at periphery
c) Extensive myxoid change
d) High cellularity
Correct answer : b) Tumor permeation between bone trabeclae at periphery