OrthoNet

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 #)