DISCUSSION
Osteochondromas, which may be present in up to 3% of the general population, are the most common benign bone tumors.1-3 An osteochondroma is a cartilage-capped bony projection that arises on the external surface of the bone; it contains a marrow cavity that is continuous with the underlying bone.2,4 The majority of osteochondromas are solitary, accounting for perhaps 85% to 90% of all such lesions, and they are typically nonhereditary; the remaining 10% to 15% of osteochondromas are hereditary multiple osteochondromas or exostoses1,2 (see “Definition of Multiple Exostoses Syndrome”2,5,6,7).
Most lesions are painless and slow growing, and they usually occur in children and adolescents.2 They typically stop growing at skeletal maturity with the closure of the growth plates.3,8,9 There is no predilection for males or females in single lesions.2
Solitary osteochondromas typically appear in the lower extremities and at long tubular bone metaphyses,1-3,10 especially on the femur, humerus, tibia, spine, and hip. Any part of the skeleton can be affected, but 30% of lesions occur on the femur and 40% at either the proximal metaphysis of the tibia or the distal metaphysis of the femur.2,11
Most osteochondromas are asymptomatic and are found incidentally.1,3 However, some patients present with local pain as a result of irritation to adjacent structures, limitation of joint motion, growth disturbance, or fracture of the pedicle.3,4,9,11,12 A very small proportion of patients (no more than 1%) with solitary osteochondromas experience malignant transformation.2,3,6,7 No particular blood work is recommended for patients with solitary osteochondromas.2