Abstract
Background: 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.
Case Report: A 19-year-old woman presented with a painless swelling above her left ankle, gradually increasing in size, of 2 years duration. Plain radiographs & MRI showed a lesion at the distal tibia eccentrically located, having a sclerotic rim all around with thinning at the outer cortex but with no evidence of soft tissue involvement. Curettage and bone grafting were performed. Tissue on histopathological examination revealed chondromyxoid fibroma.
Conclusions: 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 case demonstrates that 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.

Keywords: Chondromyxoid fibroma, subperiosteal, Myxoma, Tibia