From the archives of the AFIP - Imaging of osteochondroma: Variants and complications with radiologic-pathologic correlation

Osteochondroma represents the most common bone tumor and is a developmental lesion rather than a true neoplasm. It constitutes 20%-50% of all benign b one tumors and 10%-15% of all bone tumors. Its radiologic features are ofte n pathognomonic and identically reflect its pathologic appearance. Osteocho ndromas are composed of cortical and medullary bone with an overlying hyali ne cartilage cap and must demonstrate continuity with the underlying parent bone cortex and medullary canal. Osteochondromas may be solitary or multip le, the latter being associated with the autosomal dominant syndrome, hered itary multiple exostoses (HME). Complications associated with osteochondrom as are more frequent with HME and include deformity (cosmetic and osseous), fracture, vascular compromise, neurologic sequelae, overlying bursa format ion, and malignant transformation. Malignant transformation is seen in 1% o f solitary osteochondromas and in 3%-5% of patients with HME. Continued les ion growth and a hyaline cartilage cap greater than 1.5 cm in thickness, af ter skeletal maturity, suggest malignant transformation. Variants of osteoc hondroma include subungual exostosis, dysplasia epiphysealis hemimelica, tu rret and traction exostoses, bizarre parosteal osteochondromatous prolifera tion, and florid reactive periostitis. Recognition of the radiologic spectr um of appearances of osteochondroma and its variants usually allows prospec tive diagnosis and differentiation of the numerous potential complications, thus helping guide therapy and improving patient management.