Osteochondroma

Excerpt

Osteochondromas represent the most common bone tumor accounting for 20 to 50% of all benign osseous tumors. Osteochondromas are surface bone lesions composed of both cortical and medullary bone with hyaline cartilage caps. The presence of cortical and medullary continuity of the tumor with the underlying bone is a pathognomonic feature that establishes the diagnosis. Osteochondromas may be solitary or multiple. The multiple form is an autosomal dominant syndrome referred to as hereditary multiple exostosis (HME) or familial osteochondromatosis.

Complications associated with osteochondromas are common, including osseous deformities, fracture, bursa formation with or without bursitis, vascular compromise, neurologic symptoms, and malignant transformation. Radiographs are often diagnostic, however cross-sectional imaging may be indicated to assess for complications, assess the cartilage cap or in some challenging cases establish the presence of medullary continuity. The lesions may increase in size in skeletally immature patients, however growth or changes in morphology after skeletal maturation are concerning features for malignant transformation. The lesions may be sessile or pedunculated. When pedunculated they extend away from the nearest joint. There are multiple osteochondroma variants and/or mimickers including subungual exostosis, dysplasia epiphysealis hemimelica (Trevor disease), turret exostosis, traction exostosis, bizarre parosteal osteochondroma Tous proliferation (BPOP or Nora lesion), and florid reactive periostitis. Differential considerations would also include subperiosteal hematoma, parosteal osteosarcoma or juxtacortical chondroma, none of which would have medullary continuity.