Osteoma is a benign bony outgrowth of membranous bones. They are found
mostly on skull and facial bones. Large osteomas may develop on the
clavicle, pelvis, and tubular bones (parosteal osteomas). Soft tissue
osteomas may occur in the head, eye,and tongue,or in the extremities.
Osteomas are slow growing lesions that are normally completely asymptomatic.
They only present if their location within the head and neck region
is causing problems with breathing, vision, or hearing.
incidence is in the sixth decade. Some authors report that osteomas
occur more often in women than men (3:1). Multiple osteomas are associated
with Gardner's syndrome. The etiology of osteomas is unclear. They may
be related to osteoblastomas or may simply be a developmental anomaly.
The fact they are often found in the auditory canals of swimmers and
divers who frequent cold water suggests that in some cases they are
some type of inflammatory reaction.
The radiological appearance of osteomas depends
on their location. Central osteomas are well delineated sclerotic lesions
with smooth borders, without surface irregularities or satellite lesions.
Dr. Enneking describes the lesion as having the appearance of "one-half
of a billiard ball" attached to the underlying bone. The adjacent
cortex is not involved or weakened. Peripheral osteomas are radiopaque
lesions with expansive borders that may be sessile or pedunculated.
Osteomas need to be differentiated from enostosis which also appear
as densely sclerotic well-defined lesions on x-ray.
will show increased uptake during the active phase of growth, which
will diminish to background levels as the lesion becomes progressively
There are two types of osteomas microscopically.
Compact or "ivory" osteomas are made of mature lamellar bone.
They have no Haversian canals and no fibrous component. Trabecular osteomas
are composed of cancellous trabecular bone with marrow surrounded by
a cortical bone margin. Trabecular osteomas can be found centrally (endosteal)
or peripherally (subperiosteal).
Treatment of osteomas is only necessary if they
are symptomatic. Large osteomas should be evaluated to rule out other
i Bulloughs, Peter, Orthopaedic Pathologv (third edition), Times Mirror
International Publishers Limited, London, 1997.
Huvos, Andrew, Bone Tumors: Diagnosis, Treatment and Prognosis, W.B.Saunders,
adapted from Dr. Enneking's site.¶