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 under deep pressure. Plain X-rays showed an ill-defined intramedullary 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 tumors?

Ans. is 'b' i.e. Tumour permeation between bony trabeculae at the periphery. ChondromaThe term chondroma is used for benign neoplasm composed of cartilage. It is of two typesEnchondroma - Cartilage tumors occurring within the bonePeriosteal chondroma - Cartilage tumors occurring on the surface of the bone.ChondrosarcomaIt is the term used for a malignant tumor of cartilage.The growth potential of chondromas is limited and mostly remain stable, but they have a potential to undergo sarcomatous change.In fact, enchondromas are considered to be a low-grade chondrosarcoma.The differential diagnosis of enchondroma is a chondrosarcomaA painful chondroid neoplasm in a large bone in an adult patient can be either enchondroma or chondrosarcomaThe differentiation between a low-grade chondrosarcoma and an enchondroma can be difficult.To make a distinction between these two neoplasms, one has to make use of cytological changes the myxoid quality of stroma permeative characteristicsAmong this permeation, manifested as marrow spaces filled with the neoplasm and entrapment of preexisting bony trabeculae is the most important sign of malignancy.