Keywords
bone neoplasms - case report - fibroma, desmoplastic - orthopedic - tibia
Introduction
Desmoplastic fibroma of bone is a benign but locally aggressive fibrogenic tumor.
It is one of the less common primary bone tumor (<0.1%).[1] It tends to occur in adolescent and young adult patients, with equal sex distribution[2] This lesion shows a predilection for craniofacial bones; however, long bones are
also commonly involved, especially the distal femur and proximal tibia.[3]
There is a scarcity of literature on the features and management of this very rare
bone tumor. We report the case of a 45-year-old patient with a massive desmoplastic
fibroma of the proximal tibia.
Case Report
This case report was approved by our institution (PR(AT)95/2022). Informed consent
was obtained from the patient.
A 45-year-old male patient was referred to our clinic for evaluation of a symptomatic
lytic lesion in the proximal right tibia. Previously, he had been treated and followed-up
in another center. There, a benign bone tumor had been diagnosed 27 years before.
Curettage had been performed twice, but the tumor recurred. During previous annual
follow-ups, he had been painless and had presented almost complete functionality.
Since his life quality had not been affected and the lesion had been considered a
benign tumor, the patient had not consented to surgery.
On presentation at our center, physical examination showed evident knee deformity,
with a hard palpable medial mass measuring 10cm ([Fig. 1a]). The patient referred pain with activity and loss of functionality. X-ray images
showed a massive lytic tumor in the proximal tibia causing bone destruction ([Fig. 1b-c]). MRI images demonstrated a 13 × 15 × 13cm mass (APxMLxCC) with significant soft
tissue involvement and displacement of neurovascular structures ([Fig. 1d-f]). An ultrasound-guided biopsy for histological analysis was performed; the definitive
diagnosis was desmoplastic fibroma of bone. After discussing the case in the multidisciplinary
committee, a two-staged surgical procedure was deemed the best option.
Fig. 1 Preoperative images of the patient. A) The clinical photograph shows an evident knee
deformity, with a hard palpable medial mass measuring 10cm. B and C) Radiographic
evaluation shows a massive lytic tumor in the proximal tibia. The lesion presented
an aggressive growth with bone destruction, trabeculation and extension into the fibula
and the surrounding soft tissue. D, E and F) MRI images demonstrated a 13 × 15 × 13 cm
mass (AP × ML × CC) with significant soft tissue involvement and displacement of neurovascular
structures (white arrow). Heterogenous contrast enhancement can be observed.
The first stage consisted on resecting the tumor with wide surgical margins. In supine
position and under tourniquet, an anterior approach with an extended medial parapatellar
arthrotomy was performed. Only the anterior tibial artery was ligated; while the other
main branches of the popliteal artery and the sciatic nerve were identified and preserved
([Fig. 2a]). A wide excision of the tumor was performed. Femur was preserved during this surgical
stage since it was not affected by the tumor. Tibia was resected with 3cm wide margin.
Then, a temporary arthrodesis was performed ([Fig. 2b-d]). Local flap coverage using the medial gastrocnemius was required. The anatomopathological
study of the surgical specimen ([Fig. 3a-d]) confirmed the diagnosis of desmoplastic fibroma of bone and demonstrated negative
margins. Postoperatively, the patient presented a foot drop caused by a common peroneal
nerve palsy. It was treated with physical therapy and antiequine orthosis.
Fig. 2 Images of the first surgical stage. A) The intraoperative photograph shows the tumour
wide margin resection. The neurovascular bundle was identified, dissected and protected.
A relevant dead space can be observed. B, C and D) The intraoperative photograph and
the postoperative x-ray images show the temporary arthrodesis performed with two intramedullary
nails (anterograde tibial and retrograde femoral). Antibiotic loaded cement was used
to increase the construct stability, obliterate the dead space and locally deliver
antibiotic.
Fig. 3 Images of the anatomopathological study of the surgical specimen. Negative margins
were demonstrated. No necrosis was observed and only two mitoses per 10-HPF were counted.
Immunohistochemically, the tumor cells were positive for MDM2 and negative for sm-actin,
desmin, beta-catenin, S100, CD34. FISH for MDM2 showed a polysomy, but not amplification.
A) Macroscopic image of the sectioned surgical specimen showing the tibia with a white
lobulated tumor that extends to soft tissues with hemorrhagic areas. B) Infiltration
of the lamellar bone by the neoplasm. Image at 50x of H&E. C) Hypocellular proliferation
of spindle cells with bland nuclear features organized in a longitudinal fascicular
pattern on a collagenized stroma. Image at 400x of H&E. D) Few areas showing mildly
atypical cells arranged in a disordered pattern. Image at 400x of H&E.
The second stage was performed seven months later, aiming to achieve a functional
limb reconstruction using an endoprosthetic replacement. In supine position and under
tourniquet, the same anterior approach was performed. First, the cement spacer and
the nails were removed. Then, the prosthesis was implanted according to the usual
technique. However, on deflation of the tourniquet, a pulsatile bleeding from the
posterior aspect of the knee was seen. Tourniquet was inflated again and a complete
laceration of the popliteal artery was identified. An arterial bypass using a greater
saphenous vein autologous graft was successfully accomplished by a vascular surgeon.
After 18 months of follow-up, the tumor has not relapsed and no complications have
occurred. The patient is pain-free and has resumed his normal daily activities. However,
he presents a restricted knee ROM (0-30°) and a foot drop (40° dorsal flexion deficit)
([Fig. 4]). The patient is satisfied with the procedure (SAPS scale 22/28).
Fig. 4 Final postoperative images. A) Knee extension , B) Knee flexion C) Full plantar flexion
D) Dorsal flexion deficit (−40°). E and F) Postoperative full-length and lateral x-ray
images show a correct implantation of the endoprosthetic replacement.
Discussion
The patient presented a desmoplastic fibroma of the proximal tibia that has been followed
up annually during the last 25 years. Despite the impressive radiological images,
the patient remained asymptomatic until the last months. So far, surgical options
were left aside because the patient did not consent to surgery. Long follow-up with
conservative treatment has been previously reported in a locally advanced desmoplastic
fibroma of the ilium.[4] Although desmoplastic fibroma is frequently asymptomatic (incidental finding), it
may cause nonspecific symptoms such as swelling, pain, deformity or loss of function.[2]
Patient's radiological images were compatible with the most aggressive pattern of
desmoplastic fibroma; showing bone destruction, soft tissue extension and neurovascular
structures displacement. On radiographs, desmoplastic fibroma usually presents as
a lobulated and trabeculated well-defined lytic lesion with a narrow transition zone.
It may also have an expansile growth, even breaching the cortex and extending into
the surrounding soft tissue. The disease extension and margins are best assessed with
MRI, being the ideal technique to describe soft tissue involvement. Desmoplastic fibroma
typically shows a low to intermediate signal intensity foci on T2, which radiographically
does not correspond to calcification.[5] Furthermore, it presents heterogenous enhancement after contrast administration.
Anatomopathological study provided the definitive diagnosis of our patient's tumor.
The WHO described the desmoplastic fibroma microscopic appearance as being composed
of spindle cells in a richly collagenous matrix.[1] The main differential diagnosis is a well-differentiated low-grade fibrosarcoma.
However, desmoplastic fibroma presents minimal cytological atypia, pleomorphism and
mitoses. Macroscopically, the tumor is firm and presents a creamy-white surface with
a variegated whorled pattern.
Recurrence following simple curettage has been reported to very high; in consequence,
surgical wide excision is the current treatment of choice.[6]
[7]
[8]
[9] Evans et al.[10] reported a recurrence rate after intralesional resection of 33%, while more aggressive
techniques showed a 0% rate. They also stated that local recurrence was strongly associated
with soft tissue extension. Böhm et al.[11] analyzed 189 patients and found a recurrence rate of 55-72% after simple curettage
and 0% after wide resection. Furthermore, they highlighted the aggressive character
that can present this entity due to its risk of pathological fracture (12%) and high
recurrence rate.
On the other hand, good results after intralesional resection with less postoperative
morbidity have also been defended.[12]
[13] Some authors stated that adding adjuvant radiotherapy to intralesional curettage
may be an alternative approach when wide resection would lead to significant functional
impairment.[14] During our aggressive surgical approach, the patient suffered a common peroneal
nerve palsy and a popliteal vascular injury. Wide resection in massive tumors is not
without complications. However, we preferred this approach because the tumor size,
severe bone destruction, soft tissue extension and articular involvement made extremely
difficult to perform a successful intralesional curettage without functional impairment
or local recurrence.
We reported the case of a 45-year-old patient with a massive desmoplastic fibroma
of the proximal tibia. A two-staged surgical procedure was successfully performed:
wide resection and endoprosthetic reconstruction. Although desmoplastic fibroma is
a benign tumor, surgeons should be aware of the complexity of its treatment in the
locally advanced and aggressive cases.
