A Unique Adult-Type Distal Tibia Non-Ossifying Fibroma with Secondary Aneurysmal Bone Cysts Presenting with a Pathological Fracture

Various terms have been suggested to describe non-ossifying fibroma including fibrous cortical defect, cortical desmoid, metaphyseal fibrous defect and non-osteogenic fibroma. Regardless of the term used, they probable all refer to abnormal osteoclastogenesis at the metaphyseal region. Non-ossifying fibroma is a benign fibrogenic tumor primarily affecting children and adolescents. It is the most common childhood benign tumour in which it is found in 30% of children with open physis. It initially affects the metaphysis of long bones, most commonly the distal femur followed by the proximal and distal tibia. However, as growth takes place, the lesion extends into the diaphysis and once close to skeletal maturity it transforms into a hypersclerotic scar.