Key-words:
Craniotomy - intraorbital tumor - preoperative embolization - removal - solitary fibrous
tumors
Introduction
Solitary fibrous tumors (SFTs) are rare tumors derived from mesothelial cells or fibroblasts
and are prevalent among individuals aged 60–70 years. Although SFTs are often found
in the pleura, peritoneum, liver, kidney, and mediastinum, their occurrence in the
orbit space is quite uncommon.[[1]],[[2]],[[3]] According to the 2016 World Health Organization classification, SFTs are grouped
under the same category as hemangiopericytomas.[[4]] The malignancy grade ranges from 1 to 3, and the MIB-1 positive rate in pathology
correlates well with tumor growth speed.[[5]] The first-choice treatment is to surgically remove as much of the tumor as possible;
however, incomplete removal of a tumor through surgery leads to a high risk of recurrence,
and the tumor could spread to other parts of the body. In addition, radiation and
chemotherapy are both ineffective; consequently, complete excision is necessary for
cure.[[1]],[[3]],[[6]],[[7]] In general, large SFTs are often highly vascular, and preoperative embolization
is required to control intraoperative bleeding.[[3]],[[8]] However, due to the risk of complications such as loss of visual acuity, reports
describing embolization of orbital tumors are very few.
In the present case, a large progressive orbital SFT (maximum diameter, 33 mm) was
so rich in blood flow that embolization of the feeding artery from the ophthalmic
artery was considered necessary to achieve total removal.
Case Report
A 42-year-old man presented with painless proptosis and diplopia, which had progressed
gradually over 4 years. He was referred to the Department of Ophthalmology at our
institute. Examination revealed congestion of the bulbar conjunctiva and restricted
adduction of the eyeball on the right side. No visual impairment was found on neurological
examination. Orbital computed tomography (CT) revealed a right extraconal mass measuring
25 mm × 16 mm ×25 mm, located medially to the optic nerve [[Figure 1]]a. Magnetic resonance (MR) imaging of the mass demonstrated iso-intensity on both
T1- and T2-weighted images, containing flow-void signals within the mass [[Figure 1]]b and [[Figure 1]]c. The mass was irregularly enhanced with contrast medium, and a dynamic study demonstrated
early filling and delayed washout, indicating rich vascularity. A biopsy of the tumor
was performed and pathological analysis of the specimen revealed SFT. During biopsy,
onset of massive hemorrhage from the mass made it difficult to achieve complete hemostasis.
Subsequently, the tumor grew to 30 mm × 19 mm × 33 mm in size and extended to the
ethmoid sinus [[Figure 1]]d.
Figure 1: (a) Preoperative plain computed tomography scan of the right orbit revealing an extraconal
large mass, located medially to the optic nerve. (b) T1-weighted magnetic resonance
image revealing iso-intensity in the mass. (c) T2-weighted magnetic resonance image
revealing multiple flow-void signals contained within the mass (arrow). (d) The tumor
has substantial growth and has extended to the ethmoid sinus
The patient was transferred to our department for removal of the tumor via craniotomy.
Surgical removal of the tumor was planned after confirming the absence of metastasis
throughout the body. Preoperative cerebral angiography revealed that the tumor was
hypervascular, with feeder vessels arising from the infra- and supra-orbital arteries
and a muscular branch originating from the right ophthalmic artery [[Figure 2]]a and [[Figure 2]]b. Due to the potential risk of uncontrollable intraoperative hemorrhage, preoperative
endovascular embolization using a coil and n-butyl-2-cyanoacrylate (NBCA) was planned.
We embolized feeder vessels arising from the ophthalmic artery with coil and the infraorbital
artery with NBCA. The procedure was completed successfully with considerable decrease
in vascularization without visual complications [[Figure 2]]c.
Figure 2: (a) Cerebral angiogram demonstrating the supraorbital artery and muscular branch
originating from the right ophthalmic artery flowing into the tumor (arrows). (b)
Feeding vessel arising from the infraorbital artery (arrow). (c) Preoperative endovascular
embolization has been achieved successfully with significant decrease in vascular
supply
Surgical removal of the tumor was planned for the following day, along with otolaryngologists.
To approach the tumor, a frontal craniotomy was performed by neurosurgeons and an
endoscopic transnasal approach to the right orbit was established by otolaryngologists.
The right orbital rim and roof were removed in a one-piece fashion. Intraoperatively,
the tumor capsule was opened to reveal the fibrous characteristics of the tumor, which
was completely removed in a piecemeal manner because the tumor was too large to achieve
en bloc resection. The volume of intraoperative bleeding was limited to only 180 mL.
Histological analysis revealed that the mass consisted of spindle cells in a random
pattern, with collagen fibers and staghorn-like vascular pattern [[Figure 3]]a and [[Figure 3]]b. Immunohistochemical staining for CD34 and STAT6 was strongly positive [[Figure 3]]c and [[Figure 3]]d. The MIB-1 positive rate was 2%–4% [[Figure 3]]e, and the tumor was reconfirmed to be an SFT. Postoperatively, however, proptosis
and diplopia did not improve. MR imaging confirmed that the tumor had been totally
removed and has not recurred for 8 months since the operation [[Figure 4]]a and [[Figure 4]]b.
Figure 3: Results of pathological examination of the tumor. (a) The mass consists of spindle
cells in a random pattern, with collagen fiber and (b) staghorn-like vascular pattern
(H and E staining, x100). (c) Immunohistochemical staining, with CD34 positive for
tumor cells. (d) STAT6 is strongly positive for the nuclei of the tumor cells. (e)
The MIB-1 positive rate is 2%-4% (a and b, x100; c-e, x300)
Figure 4: Postoperative axial (a) and coronal (b) magnetic resonance images confirming nonrecurrence
of the solitary fibrous tumor 8 months since surgery
Discussion
We present a very rare case of a large orbital SFT with significant hypervascularity
fed by branches from the ophthalmic artery, which were embolized successfully using
an endovascular procedure. This tumor was completely removed via a combined transcranial
microscopic and transnasal endoscopic approach, without developing massive intraoperative
bleeding.
SFT is an uncommon neoplasm that is derived from mesothelial or fibroblast-like mesenchymal
cells and can develop in many locations in the body.[[1]],[[2]],[[3]] However, intraorbital occurrence has been so rare that, to date, approximately
90 cases have been reported.[[9]] The definitive diagnosis of SFT is dependent on characteristic histopathological
findings, such as the proliferation of spindle cells, the absence of a specific sequence
pattern, and the presence of a staghorn-like vascular pattern, with immunohistological
findings positive for CD34, STAT6, Bcl-2, vimentin, and CD99.[[1]],[[2]],[[10]] Among these, positive nucleus staining with STAT6 is available for definitive diagnosis
of SFT. The histological findings in our case were compatible with the findings described
above, confirming the diagnosis of SFT in this rare occurrence as an intraorbital
tumor.
SFT occasionally presents as clinical recurrence and is thus categorized as an “intermediate
malignancy” under the WHO Classification of soft-tissue tumors. The latest version
of the WHO Classification in 2016 placed SFT in the same category as hemangiopericytoma.[[4]] Therefore, the most effective treatment for SFT is surgical removal of the tumor
to the maximum possible extent.[[1]],[[4]],[[6]],[[7]] In addition, the hemodynamic characteristics must be understood to minimize the
risk of intraoperative hemorrhage. In cases involving large tumors, intratumoral blood
flow is often abundant, which makes it difficult to remove the tumor; therefore, preoperative
embolization is recommended. Although there are some reports of embolization for SFTs,
only three cases of embolization for intraorbital SFTs have been described [[Table 1]]. When we reviewed these reports in detail, the tumors were large and predictably
rich in blood flow according to physical examination, angiography, and MR imaging.[[11]],[[12]],[[13]] After successful preoperative endovascular embolization, the tumors were removed
completely without the occurrence of massive intraoperative hemorrhage. In addition,
embolization of feeder vessels arising from the ophthalmic artery carries the risk
of complications such as visual dysfunction. In our case, embolization was achieved
without serious complications such as occlusion of the central retinal artery.
Table 1: Characteristics of previously reported intraorbital solitary fibrous tumors and present
case performed embolization of feeding arteries before tumor removal
In this case, we selected coil and NBCA as embolic materials. We already knew in advance
that the tumor was highly vascular. Therefore, NBCA was selected to control intraoperative
bleeding because it has high hemostatic effect.[[14]] Meanwhile, NBCA has a risk of reflux into the proximal portion of feeder vessels
during injection.[[15]] To prevent the occlusion of the right ophthalmic artery by refluxed NBCA, first,
we embolized feeder vessels arising from it with a coil. And then, NBCA was successfully
injected into the infraorbital artery from the maxillary artery.
To remove a large or giant orbital tumor, it is very difficult to dissect the boundary
between the inferior part of the tumor and the surrounding structures.[[11]] Moreover, a transnasal approach using an endoscope does not enable visualization
and dissection of the inferior part of the tumor. In our case, a combined microscopic
transcranial and endoscopic transnasal approach was successfully used to completely
remove the tumor. The nasal approach not only facilitated dissection of the tumor
surroundings but also secured views at different angles and helped to establish anatomical
orientation in the orbit. To the best of our knowledge, there have been no reports
describing a two-way approach to an intraorbital SFT similar to ours. This combined
method clearly demonstrates its benefit in compensating for blinded areas in the transcranial
approach.
Histological findings included polymorphism of cells and nuclei, necrosis, and a MIB-1
positive rate, which led to the diagnosis of malignancy. As adjunctive therapy, postoperative
radiation has been recommended for residual tumor tissue.[[13]] If total removal of the tumor is achieved – as in our case – radiation therapy
is reserved for recurrence, and long-term follow-up is essential.
Conclusion
We were able to completely remove a large SFT from the orbit safely by performing
preoperative endovascular embolization to avoid massive intraoperative bleeding. In
addition, a combined transcranial and transnasal approach can provide advantages for
tumor removal and helps eliminate blinded area(s) to a great extent.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms.
In the form, the patient has given his consent for his images and other clinical information
to be reported in the journal. The patient understands that his name and initials
will not be published and due efforts will be made to conceal identity, but anonymity
cannot be guaranteed.
