Subperiosteal chondromyxoid fibroma: a report of two cases.

Chondromyxoid fibroma is a rare cartilage tumor that represents less than 1% of all bone tumors. When in a long bone, it is usually an intramedullary lesion that is eccentrically located in the metaphyseal region. Chondromyxoid fibroma may also have unusual presentations. These include intracortical lesions and subperiosteal lesions. There have been 14 reported cases of intracortical chondromyxoid fibroma, but there have been only four reports of subperiosteal lesions. A subperiosteal location, therefore, is extremely rare for a chondromyxoid fibroma. We present two new cases of subperiosteal chondromyxoid fibroma. Given its rarity, chondromyxoid fibroma is often not in the differential diagnosis of a painful, subperiosteal scalloped lesion in a long bone. Other entities such as periosteal chondroma, periosteal myxoma, subperiosteal ganglion cyst, or subperiosteal osteoid osteoma are more likely to be considered. Our cases illustrates that subperiosteal chondromyxoid fibroma, although rare, should be included in the differential diagnosis of a painful, radiographically inactive lytic lesion on the surface of a long bone.