Unusual occurrence of orbital hemangiopericytoma in the zygomatic bone of an adolescent: a case report
Eshraghi et al. Eye and Vision
Unusual occurrence of orbital hemangiopericytoma in the zygomatic bone of an adolescent: a case report
Bahram Eshraghi 0
Hadi Ghadimi 0
Zohreh Nozarian 0
0 Eye Research Center, Farabi Eye Hospital, Tehran University of Medical Sciences , Qazvin Sq, Tehran 1336616351 , Iran
Background: Hemangiopericytoma and solitary fibrous tumor are considered related variants on the same spectrum and both may essentially be the same tumor. They are infrequently encountered in the orbital region while the zygomatic bone is an extremely rare location for these neoplasms to occur. Case presentation: A 14-year-old boy presented with complaint of deformity of left infraorbital area and a firm, regular mass in the region. Orbital CT scan revealed a well-defined round isodense intraosseous lesion in the lowermost portion of the lateral orbital wall (zygomatic bone), expanding the bone and protruding anteriorly and medially. MRI showed the mass to be heterogenous and strongly enhancing with contrast medium. Inferior transconjunctival orbitotomy was performed and the mass was removed. The histopathologic examination and immunohistochemistry staining results (positive for CD34, CD31 and smooth muscle actin, but negative for CD99, S100, B-cell lymphoma 2 (bcl-2) and desmin) confirmed the diagnosis of hemangiopericytoma. The postoperative course was uneventful, with no evidence of recurrence after 5 years follow up. Conclusions: This case represents the second hemangiopericytoma reported in the zygomatic bone. Although extremely rare, hemangiopericytoma/solitary fibrous tumor might be considered in the differential diagnosis of intraosseous lesions of the orbital and zygomatic region.
Hemangiopericytoma; Orbital neoplasm; Solitary fibrous tumor; Zygomatic bone
Vascular tumors of the bone are uncommon, accounting
for 1–2% of bone tumors [
(HPC) is an infrequent vascular neoplasm that has a
propensity for soft tissues and rarely involves bony
], constituting 4.7% of primary vascular bone
]. Occurrence of hemangiopericytoma in the
zygomatic bone is extremely rare, with only one previous
report in the literature [
]. We present an adolescent
with HPC of zygoma who underwent successful surgical
A 14-year-old boy was referred with complaint of
deformity of left infraorbital region. There was fullness in
the inferolateral orbital and periorbital areas (Fig. 1) and
a firm, regular mass was palpable in the region. The
patient had felt the bulging for almost a year. No limitation
of ocular motility was observed, but lateral canthus was
slightly displaced superiorly compared to the other side.
The mass was neither painful nor tender and the
overlying skin appeared normal. Past history was
unremarkable and the patient denied history of any trauma.
Orbital CT scan revealed a well-defined round
isodense intraosseous lesion in the lowermost portion of
the lateral orbital wall, expanding the bone and
protruding anteriorly and medially (Fig. 2a and b). MRI showed
the mass to be heterogenous and strongly enhancing
with contrast medium (Fig. 2c and d). Based on available
information, the clinical suspicion of a vascular lesion
was aroused. Under general anesthesia, inferior
transconjunctival orbitotomy was performed and the mass
was exposed. The bony roof of the lesion was removed,
piecemeal excision of its contents was carried out by
curettage and hemostasis was achieved with the aid of
Surgicel (Ethicon, Somerville, NJ). Intralesional
triamcinolone acetonide was injected at the termination of
surgery before suture closure of the conjunctiva.
Histopathologic examination revealed the mass to be
composed of several slit-like vascular channels, with
occasional stag-horn appearing vessels, surrounded by
elongated bland-looking spindle cells (Fig. 3a and b).
Occasional mitotic figures (1 per 20 high power fields)
were seen. As the specimen was received as fragmented
pieces, exact evaluation of surgical margins was not
possible. However, in some of the larger pieces evaluated,
surrounding soft tissue and margins showed no tumor
involvement. Immunohistochemistry (IHC) staining
results were positive for CD34 and CD31 in endothelial
cells (Fig. 3c) and for smooth muscle actin (SMA) in
spindle cells (Fig. 3d), but negative for CD99, S100,
Bcell lymphoma 2 (bcl-2) and desmin, suggesting the
presence of HPC. The postoperative course was
uneventful, with the patient doing well without clinical or
radiologic signs of recurrence after 5 years follow up
(Figs. 4 and 5a, b).
Discussion and conclusions
HPC is a rare vascular soft-tissue tumor that can
develop anywhere in the body that has blood vessels, most
notably in lower extremities, pelvic fossa,
retroperitoneum and nasopharynx [
]. HPC rarely involves the
] and constitutes only 1.57% of orbital tumors
]. Likewise, bones are uncommonly involved in HPC,
which accounts for 4.7% of bone tumors [
Zygomatic bone involvement by intraosseous malformations
is rare and HPC of the zygoma has only been reported
once . This case represents the second reported
instance of intraosseous HPC of the zygoma. In the case
reported by Asrani et al. [
], a diagnosis of HPC of the
zygoma was made although IHC results were not
presented, and the patient was followed for 2.5 years after
HPC is primarily a tumor of adults, with the median
age of 45 years upon presentation, and without
predilection to either sex [
]. The clinical and radiological
features of HPC are not specific nor characteristic and
diagnosis is made by histopathological examination [
Patients usually present with a painless mass that grows
]. The typical appearance of HPC on the CT
scan is that of a well-circumscribed mass lesion with
occasional calcifications. MRI may better show the
heterogeneity of tumor components with areas of low and high
signal intensity on T2-weighted images representing
calcifications and thrombosis/old hematoma within the
mass, respectively [
The microscopic appearance of HPC is remarkable
for branching or “staghorn” thin-walled blood vessels
with densely packed spindle cells oriented randomly
]. Solitary fibrous tumor (SFT) is a closely related
entity that shows substantial overlap of clinical and
morphologic characteristics with HPC, and many
authors recently considered HPC and SFT as variants
belonging to the same spectrum [
]. The most
prominent differences in histopathological features
include variable cellularity, foci of dense collagenization
and strong CD34 reactivity in SFT compared with
trivial variability in cellularity, minimal collagenization
and focal CD34 staining in HPC [
HPC and SFT are indistinguishable in many instances
and most of the entities under the ill-defined term of
HPC have progressively escaped from this category,
leaving some cases that are now recognized as
cellular or malignant forms of SFT rather than HPC [
Most periocular tumors identified as HPC are
nowadays recognized as SFT and both may essentially be
the same tumor, despite some morphologic and
immunologic variations [
]. The most recent World
Health Organization (WHO) classification of soft
tissue tumors has rendered the term HPC obsolete and
categorizes all such tumors within the SFT group [
], except for those presenting in the CNS that
continue to be regarded as different entities .
Immunohistochemically, HPCs show reactivity for
CD34, vimentin, and SMA, but are mostly negative for
desmin and S-100 protein [
10, 11, 15
]. Despite the
potentially malignant/aggressive nature of HPCs, attempts
at prediction of clinical behavior of the tumor based on
pathological characteristics have largely failed, which
makes HPC an unpredictable neoplasm [
Nevertheless, features like tumor size (diameter greater than 6.
5 cm), mitotic activity (more than 4 mitoses per 10 high
power fields), hypercellularity, anaplasia, necrosis and
hemorrhage have been reported as indicators of
malignant behavior [
The treatment of choice for HPC is complete en-bloc
surgical excision whenever possible, because these
tumors are most often circumscribed or enclosed by a
]. Completeness of surgical
resection positively affects survival, while incomplete excision
(piece-meal resection) or incisional biopsy are associated
with local spread, recurrence and metastasis [
However, as in our case, complete tumor resection can
occasionally be challenging due to its friable and
highlyvascular nature [
]. Local recurrence rate is 33% [
and it typically occurs years later in those who had
piece-meal tumor resection [
]. Therefore, long term
follow up is essential to detect possible recurrence or
metastasis. Therapeutic options available for recurrent
HPC include further attempts at surgical excision,
orbital exenteration, excision combined with adjuvant
radiotherapy, and chemotherapy [
Recent advances have been made in the understanding
of the genetic basis of SFT/HPC [
]. SFTs are
consistently associated with NAB2-STAT6 gene fusions [
NAB2 (NGFI-A binding protein 2) is a transcriptional
repressor of early growth response genes (EGR1). STAT6
(signal transducer and activator of transcription 6) is a
transcriptional activator that has a role in interleukin 4
signaling . NAB2 and STAT6 are both located closely
on the chromosomal band 12q13. Their fusion results in
the production of a chimeric protein that induces cellular
proliferation through the activation of EGR1 [
has been shown that nuclear expression of the carboxy
terminal part of STAT6 was highly specific and sensitive
for SFT, allowing SFT to be distinguished from its
histological mimics .
In conclusion, an extremely unusual site of involvement
(zygomatic bone) by a rare tumor (HPC/SFT) is reported
and the relevant literature is reviewed. Complete surgical
excision provides the most effective treatment, although
postoperative follow up is required for a long period of
EGR1: Early growth response; HPC: Hemangiopericytoma;
IHC: Immunohistochemistry; NAB2: NGFI-A binding protein 2; SFT: Solitary
fibrous tumor; SMA: Smooth muscle actin; STAT6: Signal transducer and
activator of transcription 6
No grants or funds were received for this study.
BE and HG conceived the idea for the case study and followed the patient.
ZN performed the histological examination of the tumor. HG wrote the
article and BE and ZN revised it critically for important intellectual content.
All authors read and approved the final manuscript.
Ethics approval and consent to participate
The study was approved by the ethics committee of Farabi Eye Hospital,
Tehran University of Medical Sciences, Iran.
Consent for publication
Written informed consents were obtained from the parents for publication
of this Case Report and accompanying images. A copy of the written
consent is available for review by the editors of this journal.
The authors declare that they have no competing interests.
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