Developmental features and associated syndromes
In most cases, non-ossifying fibroma develops asymptomatically in adolescents and young adults. Males are slightly more frequently affected.
Pain is typically a consequence of complications—specifically, stress fractures. This is particularly common when the lesion is located in the proximal tibia.
Multiple lesions are sometimes observed and may be familial. Specific syndromes associated with the fibroma:
- Neurofibromatosis: associated in approximately 5% of multiple lesion cases.
- Jaffe–Campanacci syndrome (Jaffe–Campanacci syndrome): a combination of unilateral multiple non-ossifying fibromas with café-au-lait spots on the skin, but without the classic features of neurofibromatosis.
Radiological presentation
The diagnosis is established in the vast majority of cases based on radiography, without the need for biopsy.
Key radiographic characteristics of the lesion:
- Skeletal location: metaphysis or diametaphysis. The lesion is intracortical in origin.
- Appearance: narrow zone of transition, osteolytic lesion with a well-defined sclerotic rim. The cortex is intact.
- Shape and growth: lobulated structure. The tumor is elongated along the longitudinal axis of the bone. It originates near the epiphyseal plate (growth plate) and, as the bone lengthens, it "migrates" toward the diaphysis, extending into the medullary cavity.
- Features in slender bones: in the fibula, the fibroma may involve the entire cross-section.
- Evolution: over time, the lesion undergoes mineralization.
Magnetic resonance imaging (MRI)
Although radiography is the primary modality, MRI is helpful in complex cases, such as when the lesion mimics an aneurysmal bone cyst (ABC).
Typical MRI features of non-ossifying fibroma:
- T1-WI and PDW: low- to intermediate-intensity signal; contrast enhancement is noted.
- T2-WI: hypointense signal in 80% of cases with marginal or septal signal enhancement (hyperintensity). In 20% of cases, the lesion is entirely hyperintense.
- Marginal sclerosis: visualized as a dark (hypointense) rim.
- Reactive edema: bone marrow edema occurs predominantly in the presence of a pathologic or stress fracture.
- Secondary changes resembling an ABC may manifest as fluid-fluid levels (fluid-fluid levels).
Briefly: answers to topical questions
Which conditions should be considered in the differential diagnosis of non-ossifying fibroma?
- Aneurysmal bone cyst (aneurysmal bone cyst, ABC) — the subtle intracortical origin of NOF can lead to resemblance to an ABC.
- Benign fibrous histiocytoma (benign fibrous histiocytoma, BFH) — unlike NOF, it occurs in an older age group and has a different localization; it often resembles a giant cell tumor.
Class and exam questions
When does periosteal reaction occur in this condition?
Periosteal reaction is atypical for non-ossifying fibroma and typically occurs only as a result of a fracture.
In what case does a non-ossifying fibroma require surgical removal?
Surgical resection is indicated in rare cases where the fibroma is secretory and causes osteomalacia or vitamin D-resistant rickets.
What else to study on this topic
- Benign fibrous histiocytoma: differences from fibroma
- Giant cell tumor: an aggressive benign lesion
- Aneurysmal bone cyst as a secondary complication
- Osteochondroma and other cartilaginous tumors
- Myofibromatosis and locally aggressive bone tumors
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