Osteochondroma: MR imaging of tumor-related complications

Osteochondromas can be complicated by mechanical irritation, compression or injury of adjacent structures, fracture, malignant transformation, and pos toperative recurrence. Magnetic resonance aging represents the most valuabl e imaging modality in symptomatic cases, because it can demonstrate typical features of associated soft tissue pathology, which can be differentiated from malignant transformation. Reactive bursae formation presents as an ove rlying fluid collection with peripheral contrast enhancement. Dislocation, deformation, and signal alterations of adjacent soft tissue structures can be observed in different impingement syndromes caused by osteochondromas. M agnetic resonance imaging provides excellent demonstration of arterial and venous compromise and represents the method of choice in cases with compres sion of spinal cord, nerve roots, or peripheral nerves, depicting changes i n size, position: and signal intensity of the affected neural structures. M alignant transformation as the most worrisome complication occurs in approx imately 1% of solitary and 5-25% of multiple osteochondromas. Magnetic reso nance imaging is the most accurate method in measuring cartilage cap thickn ess, represents an important criterion for differentiation of osteochondrom as and exostotic (low-grade) chondrosarcomas. Cartilage cap thickness excee ding 2 cm in adults and 3 cm in children should raise the suspicion for mal ignant transformation. Finally, MR MR imaging can detect postoperative recu rrence by depiction of a recurrent mass presenting typical morphological fe atures of a cartilage-forming lesion.