Nonossifying fibroma
Synonyms and keywords: Fibroxanthoma; Fibrous cortical defect; NOF

# Overview
Non ossifying fibromas are present in about 30 % of children. The incidence of Non ossifying fibroma is approximately 1000-2000 per 100,000 individuals worldwide. The age distribution of Non ossifying fibroma is between 5-15 years. Men are more commonly affected than women, with a 1.9:1 ratio. In 1929, Phemister first described the term non ossifying fibroma. The exact pathogenesis of non ossifying fibroma is not fully understood. Non ossifying fibroma (NOF) typically occur in the metaphysis of the long bones. The bones often involved are femur, tibia, and fibula. The majority of patients with non ossifying fibroma are asymptomatic. Some patients with non ossifying fibroma have a complaints of pain, swelling and pathological fracture. X-ray is the diagnostic study of choice for the diagnosis of non ossifying fibroma demonstrating soap bubble like lytic lesion. Observation is the mainstay of treatment for non ossifying fibroma. Surgery in form of curettage and bone grafting is reserved for cases with high risk of pathological fracture.

# Historical Perspective
- In 1929, Phemister first described the term non ossifying fibroma.
- In 1941, Sontag and Pyle reported a radiologic description of non ossifying fibroma.
- In 1942, Jaffe and Lichtenstein described clinical findings, anatomic aspects and the natural history.

# Classification
Non ossifying fibroma can be classified based on imaging findings.

## Enneking (MSTS) Staging System
- The Enneking surgical staging system (also known as the MSTS system) for benign musculoskeletal tumors based on radiographic characteristics of the tumor host margin.
- It is widely accepted and routinely used classification.

# Pathophysiology
- The exact pathogenesis of non ossifying fibroma is not fully understood.
- Various theories have been proposed concerning the pathogenesis of non ossifying fibroma
An abnormal development extending from the growth plate.
An abnormal osteoclastic resorption at the subperiosteal level during remodeling of the metaphysis.
- An abnormal development extending from the growth plate.
- An abnormal osteoclastic resorption at the subperiosteal level during remodeling of the metaphysis.
- Non ossifying fibroma (NOF) typically occur in the metaphysis of the long bones.
- The bones often involved are femur, tibia, and fibula.
- Conditions associated:
Jaffe-Campanacci syndrome
Congenital syndrome of multiple non-ossifying fibromas and cafe au lait pigmentation, mental retardation, heart, eyes and gonads (hypogonadism) involved
Neurofibromatosis
Familial multifocal NOF
Aneurysmal bone cyst
- Jaffe-Campanacci syndrome
Congenital syndrome of multiple non-ossifying fibromas and cafe au lait pigmentation, mental retardation, heart, eyes and gonads (hypogonadism) involved
- Congenital syndrome of multiple non-ossifying fibromas and cafe au lait pigmentation, mental retardation, heart, eyes and gonads (hypogonadism) involved
- Neurofibromatosis
- Familial multifocal NOF
- Aneurysmal bone cyst

# Causes
- There are no established causes for non ossifying fibroma.

# Differentiating Non Ossifying Fibroma from Other Diseases
Non ossifying fibroma must be differentiated from following bone disorders:

# Epidemiology and Demographics
- The incidence of Non ossifying fibroma is approximately 1000 - 2000 per 100,000 individuals worldwide.
- Adolescents and children are most affected by non ossifying fibroma.
- Non ossifying fibromas are present in about 30 % of children.
- The age distribution of Non ossifying fibroma is between 5-15 years.
- Men are more commonly affected than women, with a 1.9:1 ratio.
- There is no racial predilection to non ossifying fibroma.

# Risk Factors
- There are no established risk factors for non ossifying fibroma.

# Screening
- There is insufficient evidence to recommend routine screening for non ossifying fibroma.

# Natural History, Complications, and Prognosis
- Common complications of aneurysmal bone cyst include:
Pathological fracture
Premature epiphyseal closure
Limb-length discrepancy
Angular deformity
Rare malignant transformation
- Pathological fracture
- Premature epiphyseal closure
Limb-length discrepancy
Angular deformity
- Limb-length discrepancy
- Angular deformity
- Rare malignant transformation
- Prognosis is generally excellent for non ossifying fibroma.
- Factors that influence the outcome of the non ossifying fibroma include:
Young age
Open growth plates
Metaphyseal location
- Young age
- Open growth plates
- Metaphyseal location

# Diagnosis

## Diagnostic Study of Choice
- X-ray is the diagnostic study of choice for the diagnosis of non ossifying fibroma.
- X-ray findings include:
Metaphyseal eccentric "bubbly" lytic lesion surrounded by sclerotic rim
Cortex may be expanded and thin
As bone grows, it migrates to diaphysis and the lesions enlarge.
Lesions become sclerotic as patient approaches skeletal maturity.
- Metaphyseal eccentric "bubbly" lytic lesion surrounded by sclerotic rim
- Cortex may be expanded and thin
- As bone grows, it migrates to diaphysis and the lesions enlarge.
- Lesions become sclerotic as patient approaches skeletal maturity.

## History and Symptoms
- The majority of patients with non ossifying fibroma are asymptomatic.
- Some patients with non ossifying fibroma have a positive history of:
Pain
Swelling
Pathological fracture
- Pain
- Swelling
- Pathological fracture

## Physical Examination
- Patients with non ossifying fibroma usually appear well.
- Common physical examination findings of non ossifying fibroma include:
Asymptomatic
Pain if associated with pathological fracture
- Asymptomatic
- Pain if associated with pathological fracture
- Findings associated with Jaffe-Campanacci syndrome include:
Cafe-au-lait spots
Multiple nevi
Hypogonadism
Ocular abnormalities
- Cafe-au-lait spots
- Multiple nevi
- Hypogonadism
- Ocular abnormalities

## Laboratory Findings
- There are no diagnostic laboratory findings associated with non ossifying fibroma.

## Electrocardiogram
- There are no ECG findings associated with non ossifying fibroma.

## X-ray
- Three views of affected bone or joint are recommended.
- X-ray findings include:
Metaphyseal eccentric "bubbly" lytic lesion surrounded by sclerotic rim
Cortex may be expanded and thin
As bone grows, it migrates to diaphysis and the lesions enlarge.
Lesions become sclerotic as patient approaches skeletal maturity.
- Metaphyseal eccentric "bubbly" lytic lesion surrounded by sclerotic rim
- Cortex may be expanded and thin
- As bone grows, it migrates to diaphysis and the lesions enlarge.
- Lesions become sclerotic as patient approaches skeletal maturity.

## Echocardiography or Ultrasound
- There are no echocardiography/ultrasound  findings associated with non ossifying fibroma.

## CT scan
- Computed tomography (CT) is useful in predicting the fracture risk.
- CT scans may depict a central lucency.
- CT scan may confirm a minimally displaced fracture.
- It may also be helpful in preoperative planning in unusual locations such as the femoral neck.

## MRI
- Magnetic resonance imaging (MRI) are similar to those from CT scan.
- MRI demonstrates a characteristic low signal on both T1 and T2 sequences without enhancement.
- High signal on T2 can be seen with an associated stress fracture.

## Other Imaging Findings
- There are no other imaging findings associated with non ossifying fibroma.

## Other Diagnostic Studies
Biopsy
- Biopsy finding of non ossifying fibroma includes:
Bland fibroblastic component with a few histiocytes, myofibroblast cells, and giant cells.
Marked proliferations of spindle cells arranged in a storiform pattern.
Hemosiderin deposits also are found.
Some leukocyte infiltration may be present.
- Bland fibroblastic component with a few histiocytes, myofibroblast cells, and giant cells.
- Marked proliferations of spindle cells arranged in a storiform pattern.
- Hemosiderin deposits also are found.
- Some leukocyte infiltration may be present.

# Treatment

## Medical Therapy
- Observation is the mainstay of treatment for non ossifying fibroma.

# Observation
Indications
- First line of treatment
- Most lesions resolve spontaneously and progressively re-ossify as child enters 2nd and 3rd decade of life
Technique
- Radiographs at 6, 12months, then annually until reossified

## Casting
Indication
- Pathologic fracture especially in the pediatric population.

## Surgery
Indication
- Unstable fractures
- High risk of pathologic fracture
Technique
- The surgical approach involves exposing the fracture site and developing a cortical window to curette the tumor.

## Primary Prevention
- There are no established measures for the primary prevention of non ossifying fibroma.

## Secondary Prevention
- There are no established measures for the secondary prevention of non ossifying fibroma.