Condition	Characteristics
Enchondroma	Benign appearance with irregular calcification (“popcorn” or “stippled” lesion); most common in the metaphysis or diaphysis of the hand, distal femur, proximal humerus, and tibia; may be painful because of irritation of the overlying soft tissue
Fibrous dysplasia	Ground-glass appearance of the matrix with sharp and well-defined sclerotic margin; most common in the metaphysis of the femur and tibia; bowing deformity and pathologic fracture may occur
Nonossifying fibroma	Geographic appearing, cortically based eccentric lesions found in the medullary cavity of long bones; usually asymptomatic and can occur before 30 years of age; more common in children and adolescents
Osteochondroma	Bony outgrowths that usually communicate with the intramedullary bone canal; usually occur in the metaphysis of long bones of children and adolescents
Osteoid osteoma	Well-circumscribed, 1- to 2-cm lesion with osteoblastic nidus and a surrounding sclerotic border; most common in male adolescents; usually located in the distal femur or proximal tibia; often causes pain at night overlying a hard mass