Desmoplastic fibroma is an extremely rare tumor with
less than 200 cases in the published literature. It is a slowly progressing
tumor with well-differentiated cells that produce collagen. This benign
tumor is characterized by aggressive local infiltration. It occurs most
often in the first 3 decades and is found equally in men and women. The
most common site is the
mandible, followed by the femur and pelvis. Clinical findings include
pain late in the clinical course and swelling. It may present as an effusion
if near a joint. Only 12% present with a pathological fracture.
The diagnosis of desmoplastic fibroma is difficult
to make radiologically. Plain xray shows an osteolytic, expansile, medullary
lesion with well defined sclerotic margins. The oval tumor is often found
in the metaphysis aligned with the long axis of the bone. There is usually
thinned cortex and the fine intra-lesional trabeculae give a lobulated
appearance that is described
as "soap-bubbly". A CT scan is only useful to further demonstrate
cortical breakthrough. MRI demonstrates the separation of the intraosseus
tumor from the bone. The radiological differential includes non-ossifying
fibroma, giant cell tumor, UBC, ABC and fibrous dysplasia.
Grossly, desmoplastic fibroma has a grayish to yellowish
white color and a rubbery consistency. The edges are irregular, round
and blunt. The tumor has occasional cystic foci with clear fluid.
Microscopically, the tumor has interlacing bundles
of dense collagen and low cellularity. The fusiform cells that are present
have no atypia and the nuclei are ovoid or elongated. The differential
of the tumor includes spindle cell tumors, most specifically low grade
fibrosarcoma. The desmoplastic fibroma does not have the cellularity,
mitotic activity or pleomorphism of a
fibrosarcoma but the distinction can be difficult and is sometimes made
clinically. The edge of the tumor may resemble fibrous dysplasia, but
under polarized light lamellar structures are obvious.
Treatment of desmoplastic fibroma is marginal or wide
surgical excision. Rates of recurrence are 55-72% without resection and
17% with resection.2 Recently, one study has recommended "aggressive
curettage" as a surgical option. 3
1Bohm, P. et al, Desmoplastic Fibroma of Bone, Cancer.
78( 5): 1011-1023, September 1, 1996.
2Bohm, P. et al.
3Nishida, J et al., Desmoplastic Fibroma, Clinical Orthopaedics
and Related Research, 320: 142-148., Nov., 1995.
Bullough, Peter, Orthopaedic Pathology (third edition), Times Mirror
International Publishers Limited, London, 1997.
Huvos, Andrew, Bone Tumors: Diagnosis, Treatment and Prognosis,
W.B. Saunders, Co., 1991.