Nonossifying fibroma

Nonossifying fibroma (also known as NOF or fibrous cortical defect) is a benign, non-cancerous tumor that typically occurs in the long bones of children and adolescents. Despite its name, a nonossifying fibroma is not a true fibroma, but rather a developmental anomaly of bone growth.

Epidemiology

Nonossifying fibromas are the most common benign bone lesions in children, accounting for approximately 30% of all benign bone tumors. They are typically found in children and adolescents between the ages of 5 and 15, with a slight male predominance.

Pathophysiology

Nonossifying fibromas are thought to arise from the periosteum, the fibrous tissue that covers the outer surface of bone. They are characterized by the presence of fibrous tissue and scattered giant cells, which can cause the bone to weaken and potentially fracture. Despite this, they are typically asymptomatic and are often discovered incidentally on radiography.

Clinical Presentation

Most nonossifying fibromas are asymptomatic and are discovered incidentally on radiographs taken for other reasons. When symptoms do occur, they are typically related to a pathologic fracture or to the tumor impinging on nearby structures. Symptoms may include pain, swelling, and limited range of motion.

Diagnosis

The diagnosis of a nonossifying fibroma is typically made based on the characteristic appearance on radiographs. The lesion is typically well-defined, with a thin rim of sclerotic bone surrounding a radiolucent center. Magnetic resonance imaging (MRI) may be used to further characterize the lesion and to assess for any associated pathologic fractures.

Treatment

Treatment of nonossifying fibromas is typically conservative, as most lesions will spontaneously regress as the child grows. In cases where the lesion is large, causing symptoms, or associated with a pathologic fracture, surgical intervention may be necessary. This typically involves curettage of the lesion and bone grafting.

Prognosis

The prognosis for nonossifying fibromas is generally excellent. Most lesions will spontaneously regress with skeletal maturity, and complications such as pathologic fractures are relatively rare.