Tumor biology and incidence
- Benign lesion of cortical bone located in metaphysis
- Generally latent
- Common lesions; many go without diagnosis
- Approximately 5% of all investigated benign bone tumors
- Actual incidence probably much higher as many are asymptomatic
Age
- Most often diagnosed in children ages 4-8 years
- Symptomatic almost exclusively in children; rarely symptomatic after cessation of skeletal growth
Gender
Males are more commonly affected than females
Presentation
- Usually asymptomatic, incidental finding
- May present with a pathologic fracture or pain
Physical findings
Usually none
Plain films
Site
- Distal femur and tibia
- Eccentric and usually confined to cortex
Size
Usually less than 4 cm
Tumor effect on bone
Radiolucent, elliptical lesion withinmetaphyseal or metaphyseal-diaphyseal cortex of long bone
Bone response to tumor
- Sharply demarcated by thin sclerotic margin
- Metaphyseal neo-cortical response seen when lesion grows into metaphysis
Cortex
Lesion confined to cortex
Soft tissue mass
None
Bone scan
May demonstrate increased uptake due to bone remodeling
Differential diagnosis
- Infection
- Chondromyxoid fibroma
- Fibrous histiocytoma, non-ossifying fibroma of bone
Natural history
- Most heal spontaneously with progressive ossification
- Lesion that continues to enlarge and then encroaches on medullary cavity is designated a non-ossifying fibroma
Pathology
- Gross: Cortex is replaced with fibrous tissue with granular appearance; may have yellow areas
- Microscopic: Spindle cell proliferation with storiform arrangement
- Multinucleated giant cells and abundant iron
- Foamy histiocytes may be seen
- Usually no bone formation
Diagnosis and treatment
- Plain x-rays usually diagnostic; biopsy rarely indicated
- Observation only
- Repeat radiographs at 3 to 6 month intervals for approximately 1 year if the lesion is atypical
- Lesions usually heal spontaneously
- Treatment for the progressive painful lesion is curettage and bone graft