Periosteal chondroma: MR characteristics.

PURPOSE: The purpose of this study was to describe the MR characteristics of periosteal chondroma.

METHOD: MR images of 12 proven cases of periosteal chondroma were analyzed with reference to tumor morphology and size. MR features were correlated with radiographic and pathologic findings.

RESULTS: Tumor size ranged from 1 to 7 cm in maximum diameter with a mean value of 2.6 cm. On MR images, a soft tissue mass at the bone surface with pressure erosion of adjacent cortical bone could be identified in all cases. All lesions were bordered by a hypointense rim (100%) and frequently showed a lobulated configuration (75%). Edema of medullary bone or soft tissues was not observed in any of the cases. Signal intensity of cartilaginous tumor tissue was typically hypo-or isointense relative to muscle on T1-weighted (100%) and hyperintense relative to fat on T2-weighted (92%) and T2*-weighted (100%) MR images. Radiographically significant calcifications of the tumor matrix, present in half of the cases, caused focal signal loss on MR images of all pulse sequences. Contrast enhancement was observed predominantly at the periphery of the lesions (100%), which on pathologic examinations typically contained fibrovascular bundles, surrounding the cartilage lobules.

CONCLUSION: Periosteal chondroma appears to have a relatively typical MR appearance, which reflects the histologic composition of the lesion. In addition to radiography, MRI therefore can substantially aid in the preoperative diagnosis of this rare bone lesion.