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 cailaginous tumor. Which of the following histological features (if seen) would be most helpful to differentiate the two tumours?

Ans. is 'b' i.e., Tumour permeation between bony trabeculae at periphery Chondroma (enchondroma) Vs Chondrosarcoma o The term chondroma is used for benign neoplasm composed of cailage. It is of two types : - i) Enchondroma : - Cailage tumors occuring within the bone. ii) Periosteal chondroma : - Cailage tumors occuring on the surface of the bone. o Chondrosarcoma is the malignant tumor of cailage. Growth potential of chondroma is limited and mostly remain stable, but they have a potential to undergo malignant (sarcomatous) change to become chondrosarcoma. lnfact, enchondromas are considered to be a low grade chondrosarcoma. o A painful chondroid neoplasm in a large bone in an adult patient can be either enchondroma or chondrosarcoma o The differentiation between a low grade chondrosarcoma and an enchondroma can be difficult. o To make distinction between these two neoplasms, one has to make use of Cytological changes Myxoid quality of stroma Permeative characteristics Among these permeation, maifested as marrow spaces filled with the neoplasm and entrapment of preexisting bony trabeuculae is the most impoant sign of malignancy.