How should an asymptomatic non‑ossifying fibroma ≤5 cm in a child or adolescent be managed?

Management of Asymptomatic Non-Ossifying Fibroma ≤5 cm in Children and Adolescents

Asymptomatic non-ossifying fibromas ≤5 cm in children and adolescents should be managed with observation alone, as these benign lesions have a high rate of spontaneous regression at skeletal maturity and do not require surgical intervention unless they become symptomatic or pose fracture risk. 1

Clinical Characteristics and Natural History

Non-ossifying fibromas (NOFs) are common benign bone lesions with an estimated prevalence of 30-40% in normal children and adolescents. 1 These lesions:

• Appear as solitary, eccentric, lytic lesions in the metaphysis of long bones, most commonly in the distal femur and distal tibia 1
• Are typically asymptomatic and discovered incidentally on radiographs 2, 1
• Demonstrate spontaneous regression and ossification with skeletal maturity in the vast majority of cases 1, 3
• Migrate from metaphysis toward diaphysis with bone growth and remodeling 4

Observation Protocol for Small Asymptomatic Lesions

For asymptomatic NOFs ≤5 cm, the management approach consists of:

• Simple observation without surgical intervention, given the high rate of spontaneous regression 1
• Serial radiographic monitoring to document stability or regression of the lesion 2
• Patient and family education about the benign nature of the lesion and expected natural history 1

The rationale for observation is that these lesions typically disappear and are replaced with normal bone through natural remodeling processes as the child grows. 4

Indications That Would Warrant Surgical Intervention

While observation is appropriate for small asymptomatic lesions, surgical treatment should be considered when:

• The lesion becomes symptomatic with pain 3
• The lesion is large (generally >5 cm) with significant bone expansion 3
• There is risk of pathological fracture, particularly when bone expansion exceeds 50% of bone diameter 3, 5
• A pathological fracture has already occurred 5

In one surgical series, NOFs requiring intervention had an average bone expansion of 67.4% in the transversal plane and 77.8% in the sagittal plane, with 89% classified as Ritschl type B lesions. 3

Common Pitfalls to Avoid

• Do not mistake NOFs for more aggressive bone lesions such as aneurysmal bone cysts, which can lead to unnecessary invasive procedures 2
• Do not perform prophylactic surgery on small asymptomatic lesions, as this exposes the child to unnecessary surgical and anesthetic risks when spontaneous resolution is expected 1
• Do not delay appropriate intervention if the lesion becomes symptomatic or shows concerning features on serial imaging, as pathological fractures can occur in large lesions 5
• Ensure proper radiographic characterization showing the typical eccentric, polycyclic, well-circumscribed lytic appearance in the metaphysis to confirm diagnosis 1

Monitoring Strategy

• Obtain baseline plain radiographs to document lesion size, location, and morphological features 2
• Schedule follow-up radiographs at appropriate intervals (typically 6-12 months) until skeletal maturity or lesion resolution 2
• Reassess clinically for development of symptoms, particularly pain or functional limitation 3
• Educate families to report any new symptoms, particularly pain or trauma to the affected area 5