Non Ossifying Fibroma (NOF)

NOF
Nonossifiying Fibroma (NOF)

– metaphyseal fibrous lesion of long bones (esp around knee) in children
– advanced form of fibrous cortical defect because no longer confined to cortex but extend into medullary canal
– usu ossify by 3rd decade

Signs & Symptoms:
– painful lesion
– pathological #

Xrays:
– clearly demarcated, eccentric, multilocular expansile lesions with scalloped, sclerotic margins
– bilateral or multiple lesions common
– cortex may be attenuated in areas adjacent to lesion

Histology:
– spindle cells arranged in storiform pattern
– whorls of connective tissue interspersed with multinucleated giant cells & lipid-laden macrophages (foam cells)

Treatment:
– self-limited lesions – observation
– large lesions that encompass > 50% bone diameter may require curettage & bone grafting (impending pathologic #)