AJR 2002; 178:613-615
© American Roentgen Ray Society
Osteosarcoma Arising in a Desmoplastic Fibroma of the Proximal Tibia
Ibrahim Fikry Abdelwahab1,
Michael J. Klein2,
George Hermann3,
German C. Steiner4 and
David C. Yang1
1
Department of Radiology, New York Methodist Hospital, New York
Hospital-Cornell Medical Center, 506 Sixth St., Brooklyn, NY 11215.
2
Department of Pathology, Mount Sinai-New York University Medical Center, Mount
Sinai School of Medicine, Box 1194, One Gustave Levy Pl., New York, NY
10029.
3
Department of Radiology, Mount Sinai-New York University Medical Center, Mount
Sinai School of Medicine, Box 1234, New York, NY 10029.
4
Department of Pathology, Hospital for Joint Diseases/Orthopedic Institute, 301
E. 17th St., New York, NY 10003.
Received April 30, 2001;
accepted after revision July 5, 2001.
Address correspondence to I. F. Abdelwahab.
Introduction
Desmoplastic fibroma was first described as a distinct entity by Jaffe
[1]. It is a primary benign
fibrous tumor of the bone, histologically identical to the more common
soft-tissue desmoid tumor. Desmoplastic fibroma is a rare, nonmetastasizing
but locally aggressive tumor
[2]. The aggressive nature of
this tumor was emphasized by Inwards et al.
[3] and
Böhm et al.
[4]. We describe a case of an
osteosarcoma arising in a desmoplastic fibroma in the proximal tibia.
Case Report
A 40-year-old woman sought medical attention after trauma to her right leg.
Physical examination revealed a healthy-looking woman on crutches in no acute
distress. The proximal portion of her right leg was much larger than the left
and was tender. The range of motion in her knee was normal. She had no joint
effusion, inflammation, or skin changes. The findings on the neurovascular
examination of her extremity were normal. She had been treated 11 years
earlier for a desmoplastic fibroma of the same tibia with curettage and
packing with bone chips. Radiographs at that time showed a large expansive
radiolucent lesion involving the proximal tibia and reaching the articular
margin with pseudotrabeculations (Fig.
1A). Before current presentation, other than occasional
nondebilitating leg pain, she was doing well.
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Fig. 1A. —40-year-old woman with osteosarcoma arising in desmoplastic
fibroma. Anteroposterior radiograph of right proximal tibia shows expansive
lytic lesion with pseudotrabeculations occupying proximal end of tibia and
reaching articular margin with narrow zone of transition.
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Radiographs showed growth of the tumor since the previous examination
(Fig. 1B). MR imaging revealed
considerable fluid, tumor tissue, and interruption of the cortex (Figs.
1C and
1D). A biopsy was performed,
and 250 mL of blood-tinged fluid was aspirated. There was a risk of impending
fracture because the fluid made up most of the lesion with a little remaining
bone and some solid tumor tissue located proximally and posteriorly. Frozen
sections of the biopsied tissue revealed a malignant spindle cell neoplasm. A
radical resection of the proximal half of the tibia was then performed with
reconstruction by osteoarticular allograft. The patient had an uneventful
recovery and was discharged on crutches with a long leg cast. The final
histopathologic diagnosis was a grade III, fibroblastic-type osteosarcoma
associated with residual foci of desmoplastic fibroma
(Fig. 1E). The patient
underwent postoperative chemotherapy. Six months after surgery, she has an
active extension of the knee to within 5° of full extension and is able to
flex her knee to 110°. She has mild knee laxity compatible with the
osteoarticular allograft reconstruction. She has no evidence of local
recurrent disease or metastatic disease.
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Fig. 1B. —40-year-old woman with osteosarcoma arising in desmoplastic
fibroma. Anteroposterior radiograph obtained 11 years after A shows
expansion of lesion without permeative bone destruction or periosteal
reaction.
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Fig. 1C. —40-year-old woman with osteosarcoma arising in desmoplastic
fibroma. Axial T2-weighted fat-suppressed fast spin-echo MR image (TR/TE,
4400/96) shows bright signal with fluid—fluid levels consistent with
fluid-filled tumor.
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Fig. 1D. —40-year-old woman with osteosarcoma arising in desmoplastic
fibroma. Coronal T1-weighted fat-suppressed MR image (480/20) after injection
of gadopentetate dimeglumine shows large, nonenhanced central area consistent
with fluid surrounded by thick irregular rim of enhancement representing tumor
tissue. Note thinning and interruption of bone cortex.
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Fig. 1E. —40-year-old woman with osteosarcoma arising in desmoplastic
fibroma. Photomicrograph of histopathologic specimen of curettage—biopsy
performed 11 years after initial curettage shows, at medium power, one
curetted fragment (right) with dense collagen and sparse cellularity. This
finding is consistent with recurrent desmoplastic fibroma. Second curetted
fragment at left shows hypercellularity and nuclear enlargement even at medium
power and is consistent with fibroblastic osteosarcoma (x60). Inset
reveals unequivocal tumor osteoid in higher power photograph of hypercellular
fragment (x125). (H and E)
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Discussion
Desmoplastic fibroma is one of the rarest bone tumors. Dahlin and Unni
[5] presented nine cases
(0.11%) of desmoplastic fibroma in a series of 8,542 primary bone tumors.
There was no sex predilection, and the mean age of the patients was 23 years.
In another study with 184 patients, desmoplastic fibroma most often involved
the following bones: mandible, 23%; femur, 15%; pelvic, 13%; radius, 12%; and
tibia, 9% [4]. The clinical
characteristics were nonspecific and similar to other tumors. Some patients
had no symptoms, and their tumors were incidental findings on radiographs
obtained after a trauma or for other unrelated reasons. In most patients, pain
or a palpable mass was the reason for the radiographic examination.
Approximately 20 (12%) of 161 of patients presented with a pathologic fracture
[4].
Radiographically, desmoplastic fibroma is a lytic tumor. In long bones, it
is oval, with its longest dimension aligned with the long axis of the host
bone. Desmoplastic fibroma usually arises in the metaphysis and can reach the
end of the host bone in skeletally mature patients. The tumor sometimes arises
in the diaphysis. The zone of transition between the tumor and the normal bone
is typically narrow and well defined but not sclerotic. Within the tumor,
there are pseudotrabeculae that vary in appearance, from coarse linear strands
to lacelike, reticular patterns. The bone is often expanded, resulting from a
gradual opposition of periosteal new bone. When the cortex is breached, a
soft-tissue mass, which may either invade or displace adjacent muscles, is
often present. Distinct periosteal new bone is rare except in association with
pathologic fractures [2]. MR
imaging contributes little to the differential diagnosis. However, clear
separation of intraosseous tumor from normal bone marrow make MR imaging the
most valuable imaging modality in surgical planning and also the most suited
to reveal the extraosseous tumor component. MR imaging was also of special
value in our patient because it showed fluid—fluid levels occupying
almost the whole lesion, with solid tumor tissue at the periphery.
Pathologically, desmoplastic fibroma is formed of fibroblasts with small
nuclei, and absent or small nucleoli are present within a collagen matrix;
rarely, normal mitosis may be seen. Focal nuclear pleomorphism or any atypical
mitosis should suggest either grade I fibrosarcoma or grade I fibroblastic
intramedullary osteosarcoma, both of which are in the general category of
spindle cell sarcoma. The distinction between these tumors and desmoplastic
fibroma may be histologically subtle
[4]. Radiography is useful in
the differentiation, usually revealing a permeative pattern of bone
destruction and a wide zone of transition in low-grade fibrosarcoma. Low-grade
osteosarcoma, unlike desmoplastic fibroma, is associated with areas of
mineralized tumor matrix. Approximately 30% of desmoplastic fibromas break
through the cortex. The breaking of the cortex should not be mistaken for a
sign of malignancy [2].
Böhm et al.
[4] studied the recurrence rate
after the different procedures used in the treatment of desmoplastic fibroma.
They noticed that the recurrence rate (55%) was high in patients who had
curettage. In contrast, the recurrence rate (17%) after resections
(intralesional, marginal, or wide) was much lower. In 11 patients who had wide
resection and a minimal follow-up of 3 years (mean, 6.1 years), no recurrences
were reported. Therefore, wide resection is the ideal treatment of
desmoplastic fibroma.
Transformation of desmoplastic fibroma to sarcoma is extremely rare even
after a long course of the disease. We know of only one documented case
described by Van Blarcom et al.
[6] in which the right side of
the mandible was resected because of a destructive tumor that measured 5
x 4 x 4 cm and was histologically typical of a desmoplastic
fibroma. In this patient, the tumor recurred 2 years later and had changed
into a grade II fibrosarcoma. The patient developed two local soft-tissue
recurrent masses that were removed during the next 2 years and then developed
bilateral pulmonary metastases. Van Blarcom et al. conceded that the original
tumor possibly should have been classified as a well-differentiated
fibrosarcoma. The same case was excluded from a study by Inwards et al.
[3] of 27 cases of desmoplastic
fibromas from the Mayo Clinic. According to these researchers,
One of the cases excluded from this series was a mandibular tumor,
originally classified as desmoplastic fibroma, that later recurred and
metastasized. Although the recurrent tumor had more obvious malignant
histologic features, considering it a lowgrade fibrosarcoma seemed
reasonable.
Most authors [3,
4,
6] emphasize that lowgrade
fibrosarcoma poses the most difficult problem in histologic differential
diagnosis of desmoplastic fibroma, even for the experienced pathologist
because the features of both tumors merge imperceptibly with one another
[3,
4]. There are two additional
cases in the literature suggesting the aggressive nature of desmoplastic
fibroma. Randelli [7] described
a patient who had four recurrences of a desmoplastic fibroma in the left
fibula; the last recurrence was localized in the right iliac crest and
abdominal muscles. Böhm et al.
[4] mentioned another case of a
desmoplastic fibroma in the distal femur that was confirmed twice
histologically as a desmoplastic fibroma by open biopsy and was described by
Pranzo-Zaccaria (in Böhm et al.
[4]). Two years later, the
patient developed destructive lesions in the radius and pelvis that were
considered metastases. The patient, however, did not consent for a biopsy to
confirm the diagnosis. In these two cases, histologic confirmation was not
documented.
We know of no report of transformation of desmoplastic fibroma to an
osteosarcoma. Eleven years after the current patient was treated by curettage
and packing by allograft bone, the tumor recurred as a high-grade
osteosarcoma. Such transformation could not be detected radiographically.
There was no permeative pattern of bone destruction, periosteal bone reaction,
wide zone of transition, or matrix calcification of the original tumor. The
tumor had changed into a cavity full of fluid, as was revealed on MR imaging
and at surgery. Such a presentation is unique and extremely rare.
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Inwards CY, Unni KK, Beabout JW, Sim FH. Desmoplastic fibroma of
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Dahlin DC, Unni KK. Bone tumors, 4th ed.
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Van Blarcom CW, Masson JK, Dahlin DC. Fibrosarcoma of the mandible:
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Randelli G. I fibroma desmoidi dell'osso. Arch
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Introduction
Case Report
