-Ossifying Fibroma - Fibrous Cortical Defect
fibroma (NOF) is a well circumscribed, solitary fibrous proliferation.
This lesion is found mostly in children with 75% occurring in the second
decade. The lesion is found in males more commonly than in females and
may occur in as many as 35% of all children.' It is a non-neoplastic process
that occurs in the juxtaepiphyseal region of the long bones. The most
common site is the femur followed by the tibia .
Clinically, non-ossifying fibromas are asymptomatic and are usually discovered
as an incidental finding on x-ray. Occasionally, a larger lesion presents
as a pathologic fracture. The classic scenario is a child who has a minor
injury in a sports contest and a plain radiograph is taken in a local
emergency room. A lesion is seen and the child is referred to an
orthopaedic surgeon for evaluation. Generally, a careful history
and physical examination will show that the child's pain is related to
the nearby joint rather than the lesion, and that the pattern of the symptoms
fits that which is expected in a sprain or strain injury. If there
was pain before the injury that seems to arise from the lesion, the diagnosis
of NOF is highly suspect. Jaffe-Campanacci syndrome is a constellation
of symptoms including multiple non-ossifying fibromas, cafe-au-lait spots,
mental retardation, hypogonadism, ocular and cardiovascular abnormalities.
Non-ossifying fibromas have a very typical appearance on x-ray. They are
eccentric, multi-loculated sub-cortical lesions with a central lucency
and a scalloped sclerotic margin. There is sometimes cortical thinning
but no periosteal reaction. Serial x-rays will show the lesion migrating
away from the epiphyseal plate with time. If the lesion is
not eccentric, has no sclerotic rim, or is not multi-loculated, the diagnosis
of NOF is suspect and further evaluation is warranted. Since
these lesions may be treated by observation only without biopsy, the physician
should be quite certain of the diagnosis before formulating a treatment
plan. If any doubt exists, the advice of an orthopaedic oncology
specialist should be sought.
On gross appearance, non-ossifying fibromas have a yellow-brown color
and have a fibrous consistency. Microscopically,
dense fibroblasts are found in whorled and storiforrn patterns. Xanthoma
cells are present as well. There is no pleomorphism or atypia among the
spindle cells and there are very few mitoses.
These lesions normally regress spontaneously. The only definite indication
to treat non-ossifying fibromas is a pathologic fracture. The natural
history of these lesions is that they either spontaneously resolve or
move to the diaphysis of the bone.
Bullough, Peter, Orthopaedic Patholovv (third edition), Times
Mirror International Publishers Limited: London. 1997.
Huvos, Andrew, Bone Tumors: Diagnosis. Treatment and Prognosis,
W.B. Saunders, Co., 1991.
Kurnar, R. et al., Fibrous Lesions of Bones, Radiographics,
Marks, KE and TW Bauer, Fibrous Tumors of Bone, Orthopaedic
Clinics of North America, 20(3): July, 1989.
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