Keywords
bony erosion - extracalvarial epidermal cyst - giant swelling
Introduction
An extracalvarial epidermal cyst is a benign, uncommon type of tumor. Its incidence
is around 0.2 to 1%.[1]
[2]
[3] Epidermoid cysts of the skull of primary origin are rare. The first reported case
dates back to the 19th century by Muller.[4] In most cases, they are slow growing, benign, and congenital, and derive from the
ectodermal remnants misplaced during embryogenesis.[5] A few can also occur following a trauma.[6] Malignant changes in such tumors may occur rarely.[7] These cysts vary in size, location, and rate of progression. The most common symptom
is a long-standing, asymptomatic lump on the head. Headache, focal tenderness, seizures,
and traumatic rupture can occur. Rarely, very large lesions may be associated with
focal neurological deficits.[8] Radiological investigations include skull X-ray, computed tomography (CT), and magnetic
resonance imaging (MRI). Histopathological analysis is confirmatory for diagnosis.
Case Report
A 75-year-old gentleman presented to us in the outpatient department with complaints
of a large lump over the head for the past 40 years, which was slowly progressing
in size over the years. It was the first time in four decades that he consulted a
medical professional for the swelling as he developed mild but tolerable pain for
the last 1 month with mild itching over the swelling ([Fig. 1]). On examination, the size of the swelling was 15 cm × 13 cm × 7 cm extending over
the biparietal and posterior frontal regions. It was irregular in shape with a smooth
surface. The swelling was soft in consistency and skin over the swelling was pinchable
and the swelling was mobile. There was no engorged vein, no visible pulsation, no
localized rise in temperature, no cough impulse, and no other skin changes.
Fig. 1 Giant swelling present over the frontoparietal region.
Magnetic resonance imaging (MRI) revealed a large expansile lytic lesion of measuring
14 cm × 11 cm × 5 cm in size arising from the parietal bone causing erosion of the
bone bilaterally ([Fig. 2]). The lesion was limited to the dura, causing mass effect on the left parietal lobe
with effacement. There was no contrast enhancement.
Fig. 2 Magnetic resonance imaging (MRI) showing large expansile extradural lesion in the
parietal region causing mass effect and effacement on the left parietal lobe.
The patient was taken for surgery under general anesthesia. Posterior bifrontal skin
flap was planned and raised. Tumor tissue was covered by a pale yellow–colored capsule,
which was dissected off from the scalp layers. The capsule was densely adhered to
the pericranium. Yellow-colored pultaceous cheesy material was drained ([Fig. 3]). The capsule with tumor tissue was excised in toto. The bony defect ([Fig. 4]) was identified and the cyst wall from the dura was gently scraped. There was no
intradural extension of the tumor. Cranioplasty was done with a titanium mesh. Extra
skin was trimmed and Y-plasty was done and skin was closed in layers. The postoperative
period was uneventful. Sutures were removed on day 10 ([Fig. 5]).
Fig. 3 (A) Pultaceous cheesy material draining out and (B) pale yellow capsule of the tumor.
Fig. 4 (A) Large bony defect. (B) Cranioplasty done with titanium mesh.
Fig. 5 Postsuture removal and Y plasty flap.
Histopathology suggested laminated keratin material and cholesterol crystals with
cellular debris, which were consistent with the diagnosis of epidermal cyst ([Fig. 6]). The patient has been followed up for the past 6 months without any sign of recurrence.
Fig. 6 Histopathological slide showing cellular debris and laminated keratin with cholesterol
crystals.
Discussion
Epidermal cysts can occur in most parts of the body but are most commonly seen in
the trunk, face, neck, and genitals. They may be infected or enlarged. These cysts
are usually mobile and vary in size depending upon the time of presentation. The cause
of the bony defect is hypothesized to be persistent pressure by the expanding lesion.[9]
Intradiploic cysts constitute 25% of extracalvarial tumors, whereas the rest are intradural.[2] Differential diagnosis includes dermoid cyst, hemangioma, fibrous dysplasia, and
eosinophilic granuloma. Atypical epidermoid cysts may be difficult to distinguish
from other lytic lesions of the calvaria.[10]
Cushing stated that the aim of surgery was complete excision of the tumor along with
its capsule and thorough curettage of the dura.[11] Incomplete removal causes a recurrence rate of 8.3 to 25%.[12]
To our knowledge, very few cases of giant intradiploic epidermoid cysts with extensive
bony defects and deformation of brain have been described in the literature ([Table 1]). The time interval between the appearance of the lump and first consultation for
it is about four decades, which is uncommon and corresponds only to few other case
reports, and is the first case in which a slowly progressive, painless proptosis of
an eye was described.[13] In the other case report, the patient presented with dizziness and focal retinal
detachment.[14] Among the others cases, either the presentation was within few years or the pathology
was purely intracranial.
Table 1
Similar cases in the literature
|
Sl. no.
|
Article title
|
Year of publication
|
Authors
|
|
1
|
Giant intradiploic epidermoid tumor of the occipital bone: case report
|
1990
|
Guridi et al[1]
|
|
2
|
Intradiploic epidermoid cysts of the skull: report of 10 cases and review of the literature
|
1990
|
Ciappetta et al[2]
|
|
3
|
Intradiploic primary epithelial inclusion cyst of the skull
|
2006
|
Kalgutkar et al[5]
|
|
4
|
Intradiploic frontal epidermoid cyst in a patient with repeated head injuries: is
there a causative relationship?
|
2006
|
Locatelli et al[6]
|
|
5
|
A giant intradiploic epidermoid cyst with perforation of the dura and brain parenchymal
involvement
|
2007
|
Cho et al[9]
|
|
6
|
Giant intradiploic epidermoid cyst with large osteolytic lesions of the skull: a case
report
|
2012
|
Krupp et al[14]
|
Our patient experienced no restrictions of his daily life activities or social contacts
pre- or post-op. Post-op his head felt light and he no longer felt different from
the rest of the people around physically. Surprisingly our patient never experienced
problems laying down on either side preoperatively. Cranioplasty was done in our patient
to avoid postoperative complications and for good cosmesis.
Conclusion
Extracalvarial epidermal cysts are benign, slow-growing tumors. Unfortunately, even
in 2024 there are patients living with such large resectable tumors. Despite their
large size, they do not cause debilitating symptoms. If the patient is willing, surgery
should be advised to them, as complications occur very rarely postoperatively. Cranioplasty
should be performed in large bony defects. Complete removal of the capsule is a must
while dealing with such tumors.
