Concurrent enchondroma and periosteal chondroma of the humerus mimicking chondrosarcoma.

A case of concurrent enchondroma and periosteal chondroma of the right proximal humerus in a 19-year-old woman is reported. Radiographs and CT scans showed a periosteal lesion with saucerization and spicula-like mineralization of the lateral aspect of the right proximal humerus and an ill-defined irregular lucency with stippled calcifications of the medullary cavity adjacent to it. MRI showed a long intramedullary lesion in addition to the surface lesion. There was no cortical disruption by imaging and gross examination. Histologically, both lesions showed benign cartilaginous tumors; concurrent enchondroma and periosteal chondroma of the humerus was therefore diagnosed. This combination in the same bone in a patient without enchondromatosis is exceedingly rare. Radiographic features may be confused with chondrosarcoma.