Non-ossifying fibroma

A benign bone tumor

Non-ossifying fibroma (NOF) is a benign bone tumor that typically occurs in the metaphysis of long bones in children and adolescents. It is one of the most common benign bone lesions and is often discovered incidentally on X-rays taken for other reasons.

Pathophysiology

Non-ossifying fibromas are composed of fibrous tissue and are considered a type of fibrous cortical defect. They are characterized by a proliferation of spindle-shaped fibroblasts and histiocytes, often with scattered multinucleated giant cells. The lesion is typically well-circumscribed and located in the cortex of the bone.

Clinical Presentation

Most non-ossifying fibromas are asymptomatic and are found incidentally. However, larger lesions may cause pain or pathological fractures, especially if they weaken the structural integrity of the bone.

Diagnosis

Diagnosis is primarily made through imaging studies. On X-ray, non-ossifying fibromas appear as well-defined, eccentric, lytic lesions with a sclerotic margin. They are often located in the metaphysis of long bones such as the femur or tibia.

Non-ossifying fibroma

Advanced imaging techniques such as CT scan or MRI can be used to further characterize the lesion. On CT, a mature non-ossifying fibroma may show a well-defined, cortically based lesion with a sclerotic rim.

Mature non-ossifying fibroma CT

Treatment

In most cases, non-ossifying fibromas do not require treatment and are monitored with periodic imaging. If the lesion is large or symptomatic, surgical intervention may be necessary. This can include curettage and bone grafting to stabilize the bone and prevent fracture.

Prognosis

The prognosis for non-ossifying fibroma is excellent. These lesions often spontaneously regress as the child grows, and they rarely cause long-term complications. Malignant transformation is extremely rare.

Related pages

• Bone tumor
• Fibrous dysplasia
• Osteochondroma