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Orbital Intradiploic Giant Epidermoid Cyst
Gonzalo Blanco, MD, PhD;
Rosario Esteban, MD, PhD;
David Galarreta, MD;
M. Antonia Saornil, MD, PhD
Arch Ophthalmol. 2001;119:771-773.
ABSTRACT
We report a case of an intradiploic epidermoid cyst of the lateral orbital
wall that resulted in proptosis and downward displacement of the left eye.
Computed tomography and magnetic resonance imaging revealed a bone-destroying
mass involving the frontal, sphenoid, and zygomatic bones that extended into
the orbit, temporalis, and anterior cranial fossa. Complete surgical removal
was performed through a lateral orbitotomy. The lateral wall was reconstructed
with a porous polyethylene sheet. The cyst has not recurred after 18 months
of follow-up.
INTRODUCTION
Dermoid and epidermoid cysts are among the most common orbital tumors,
comprising 3% to 9% of all orbital masses; diagnosis usually occurs during
infancy or early childhood.1-2
These tumors are choristomas that arise from epidermal tissues trapped along
bony suture lines during embryologic development and more rarely after trauma.
Epidermoid cysts account for less than 1% of cranial tumors; 25% are intradiploic
and 75% are intradural.3 Fewer than 20 well-documented
cases of intradiploic epidermoid cysts of the bony orbit have been reported
in the literature and the involvement of multiple orbital bones is exceptional.4
We report a case of a giant epidermoid cyst involving 3 orbital bones
(sphenoid, zygomatic, and frontal) that extended into the orbit, temporalis,
and anterior cranial fossa. The cyst manifested clinically as progressive
exophthalmos.
REPORT OF A CASE
A 22-year-old healthy woman was referred to our clinic with a 6-month
history of progressive downward displacement of her left eye (Figure 1). The visual acuity was 20/20 bilaterally and the intraocular
pressure was 16 mm Hg bilaterally. A left 3-mm proptosis and a 7° hypotrophy
that did not induce diplopia also were noted. Slitlamp and fundus examination
findings were normal. The workup included computed tomography (CT) and magnetic
resonance imaging (MRI). The CT scan revealed a bone-destroying mass involving
the lateral wall and orbital roof. The mass was isodense with the brain parenchyma,
had well-defined sclerotic borders, and had invaded the orbital cavity and
temporalis fossa (Figure 2). No
enhancement with intravenous contrast was observed. The MRI scan showed a
relatively hypointense signal on T1-weighted images and hyperintense signal
on T2-weighted images. Coronal sections showed invasion into the anterior
cranial fossa without affecting the brain parenchyma (Figure 3). A biopsy of the mass was performed through a lateral
orbitotomy. Histopathologic study revealed abundant degenerated keratin debris
and occasional fragments of a stratified and keratinized epithelium without
skin appendages, which led to the diagnosis of epidermoid cyst (Figure 4). The same surgical approach was used to completely excise
the orbital mass, but this time a bone flap was obtained. The lesion was removed
piecemeal with extensive dissection, excision, and profuse irrigation to ensure
complete removal of the cyst. A large defect in the lateral wall was repaired
with a 1.5-mm porous polyethylene sheet (Medpor; Porex Surgical Inc, College
Park, Ga). Exhaustive histopathologic study of serial sections from all the
excised fragments disclosed the same findings described on the biopsy specimen.
Since no skin appendages were detected, the diagnosis of epidermoid cyst was
confirmed. Eight months after surgery, the aesthetic results were satisfactory
(Figure 5) and no recurrence was
detected on CT (Figure 6). No clinical
sign of recurrence has been observed during an 18-month follow-up.
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Figure 1. Left proptosis and downward displacement
of the left eye. A significant fullness in the temporal aspect of the left
upper lid is also noted.
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Figure 2. A large bone-destroying mass with
sclerotic borders is detected on the lateral wall of the left orbit on computed
tomographic axial section. The lesion, mainly located on the greater wing
of the sphenoid, extends into the zygomatic bone, temporalis fossa, and orbit.
Note the similar radiologic density of both the lesion and brain parenchyma.
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Figure 3. Magnetic resonance imaging coronal
section on T1-weighted image. The heterogeneous hypointense lesion displays
marked growth into the anterior cranial fossa through a bone defect on the
frontal bone (roof of the orbit). Significant extension into the orbit and
moderate temporalis fossa invasion are also appreciated.
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Figure 4. Photomicrograph shows abundant
degenerated keratin debris and a stratified squamous epithelium without skin
appendages characteristic of an epidermoid cyst (hematoxylin-eosin, original
magnification x40).
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Figure 5. The patient 8 months after surgical
excision of the mass, left upper lid blepharoplasty, and ptosis repair. Satisfactory
aesthetic results were achieved with clinical resolution of proptosis and
orbital dystopia.
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Figure 6. Computed tomographic axial section
demonstrates complete surgical removal of the epidermoid cyst and absence
of recurrence. The polyethylene sheet used to avoid enophthalmos is seen as
a radiolucent line parallel to the lateral wall.
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COMMENT
The term "dermoid" has been used extensively to describe dermoid and
epidermoid cysts in the orbit; however, they are different entities. Both
are cystic choristomas filled with keratin, cholesterol clefts, or degenerated
blood components, and produced by keratinizing squamous epithelium; but whereas
true dermoids have skin appendages on their walls, epidermoid cyst walls do
not have these appendages.2 Interestingly,
their clinical behaviors usually differ. Dermoid cysts are common, diagnosed
during infancy or early childhood, located superficially or in the anterior
orbit, commonly mold bone, and rarely induce bone lysis (dumbbell-dermoids).
Conversely, epidermoid cysts are rare lesions that are usually diagnosed later
in life, likely because they are deeper in the orbit, and they typically develop
within orbital bones diploë.4-5
In fact, intradiploic epidermoids are rare tumors more commonly located in
the skull bones, particularly in the temporal or frontal bone.3
Only about 100 cases have been described in the literature, with fewer than
20 well-documented cases located in the bony orbit.3-4
As in our case, orbital intradiploic epidermoid cysts are commonly located
in the lateral wall.4, 6 They may
invade other orbital walls and extend into the orbit, temporalis fossa, or
cranial cavity. In our patient, all these growth patterns occurred, which,
combined with its significant size, accounted for the name "giant" epidermoid
cyst. A similar case with middle cranial fossa involvement was reported by
Rumelt et al.7
The clinical characteristics of orbital intradiploic epidermoid cysts
were well described by Eijpe et al.4 The most
common clinical manifestation is unilateral proptosis, which is eventually
associated with extraocular muscle impairment or diplopia. Nonophthalmologic
signs include headache and other neurologic symptoms that are especially common
when intracranial extension occurs. Cranial or significant temporalis fossa
invasion may induce pulsatile proptosis or proptosis associated with mastication,
respectively.3-4 In the present
case, exophthalmos and downward displacement of the left eye were the main
symptoms that were only associated with ipsilateral headache.
Both CT and MRI play an essential role in diagnosing epidermoid cysts
and determining the surgical excision strategy. Three types of secondary bone
changes have been described: sclerosis, erosion, and fossa formation with
bone attenuation.3, 7 Characteristic
bone destruction with sclerotic borders was the CT finding in our case. Despite
its limited ability to define bone changes, MRI has a definitive role in further
characterization of these lesions: both dermoid and epidermoid cysts display
a highly suggestive hyperintense signal on T2-weighted images.3
Moreover, MRI may more accurately demonstrate intracranial extension, as in
this case.8 Differential diagnosis in our case
included eosinophilic and cholesterol granuloma.
Most of these tumors are surgically managed through a coronal approach
to provide wider exposure, and a craniotomy is performed to deal with intracranial
extension.8 In our case, because of the low
probability of brain involvement, a lateral orbitotomy with a bone flap was
preferred, which allowed for good exposure and excision of the cyst through
a small cutaneous incision. The importance of complete excision must be emphasized
because incomplete excision may lead to chronic granulomatous inflammation
or recurrence; moreover, recurrence is associated with increased risk of malignancy.4, 8 In the present case, the cyst has not
recurred after an 18-month follow-up.
In summary, the present case is an exceedingly rare occurrence of unilateral
proptosis resulting from an intradiploic epidermoid cyst primarily located
in the bony orbit and secondarily extending to the cranial cavity and temporalis
fossa. Its clinical presentation, imaging characteristics, and management
rationale are also stressed. Intradiploic epidermoid cyst must be considered
in the differential diagnosis of benign bone-destroying lesions affecting
the orbit.
AUTHOR INFORMATION
Accepted for publication December 5, 2000.
Corresponding author: Gonzalo Blanco, MD, PhD, Instituto Universitario
de Oftalmobiología Aplicada (IOBA), Universidad de Valladolid, Ramón
y Cajal 7, 47005 Valladolid, Spain (e-mail: gonzalo{at}ioba.med.uva.es).
From the Instituto Universitario de Oftalmobiología Aplicada,
Universidad de Valladolid (Drs Blanco, Galarreta, and Saornil), and the Departments
of Ophthalmology (Drs Blanco, Galarreta, and Saornil) and Radiology (Dr Esteban),
Hospital Universitario, Valladolid, Spain.
REFERENCES
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7. Rumelt S, Harsh IV GR, Rubin PAD. Giant epidermoid involving 3 cranial bones. Arch Ophthalmol. 1997;115:922-924.
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8. Fukuta K, Jackson IT. Epidermoid cyst and cholesterol granuloma of the orbit. Br J Plast Surg. 1990;43:521-527.
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SECTION EDITOR: W. RICHARD GREEN, MD
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