PERIOSTEAL CHONDROMA MASQUERADING AS OSTEOCHONDROMA

The authors describe two cases of a lesion that closely resembled oste ochondroma occurring at the posterior aspect of the distal femur in th e popliteal region. Histopathologic examination after open biopsy reve aled that the lesions were periosteal chondromas, and they were resect ed. Osteochondroma, particularly that undergoing malignant transformat ion, should perhaps be considered in the differential diagnosis of per iosteal chondroma; the key to distinguishing between these two lesions is the separation of periosteal chondroma from the medullary portion of the bone by intervening cortex.