- Department of Neurosurgery, King Abdullah Medical City, Makkah, Saudi Arabia
- Department of Pathology, College of Medicine, Umm Al-Qura University, Makkah, Saudi Arabia
- Department of Community Medicine, King Edward Medical University, Lahore, Pakistan
Correspondence Address:
Ahmed Adel Farag, Department of Neurosurgery, King Abdullah Medical City, Makkah, Saudi Arabia.
DOI:10.25259/SNI_170_2025
Copyright: © 2025 Surgical Neurology International This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-Share Alike 4.0 License, which allows others to remix, transform, and build upon the work non-commercially, as long as the author is credited and the new creations are licensed under the identical terms.How to cite this article: Ahmed Adel Farag1, Mohammad Ghazi Abdoh1, Yoseri Jameel Alhamss1, Abdelmoneim Almoatazbellah Kamar1, Zaina Brinji1, Alaa Alkhotani2, Yahya Mubasher Mir3, Hussein Kheshaifati1. An atypical intradiploic epidermoid cyst, radiological findings, and surgical management. 16-May-2025;16:183
How to cite this URL: Ahmed Adel Farag1, Mohammad Ghazi Abdoh1, Yoseri Jameel Alhamss1, Abdelmoneim Almoatazbellah Kamar1, Zaina Brinji1, Alaa Alkhotani2, Yahya Mubasher Mir3, Hussein Kheshaifati1. An atypical intradiploic epidermoid cyst, radiological findings, and surgical management. 16-May-2025;16:183. Available from: https://surgicalneurologyint.com/?post_type=surgicalint_articles&p=13558
Abstract
Background: Epidermoid cysts are benign, slow-growing, and extra-axial lesions that typically develop between the brain structures. Intradiploic and intra-axial involvement is exceptionally rare. We present a case of an intradiploic epidermoid cyst with distinct clinical and radiological features. This case highlights an unusual location and radiological presentation of an epidermoid cyst located within the skull base and may be misdiagnosed as other pathologies.
Case Description: A 44-year-old male presented with a dull, aching frontal headache and slowly growing right frontal swelling, worsening over several months. On examination, the patient had a hard, non-tender, non-mobile right frontal swelling above the right orbit, with an unremarkable neurological examination. Computed tomography brain revealed an extra-axial hypodense lesion in the right frontal region, causing bony thinning and focal defects in the roof of the right orbit and the zygomatic process of the frontal bone. A mild mass effect on the superior rectus muscle and adjacent brain parenchyma was noted, with the left midline shift and effaced sulci. Magnetic resonance imaging (MRI) brain showed heterogeneous signals in both T1 and T2 as well as a central area of restricted diffusion in diffusion-weighted imaging, the blood products indicated by susceptibility-weighted imaging blooming artifacts, which were suggestive of hemorrhage. The radiological differential diagnosis included an epidermoid cyst, arachnoid cyst, dermoid cyst, abscesses, metastasis, and an aneurysmal bone cyst. The patient underwent a right frontal craniotomy and excision of the cyst. Intraoperative gross inspection and histopathological analysis confirmed the diagnosis of an intradiploic epidermoid cyst.
Conclusion: Epidermoid cysts occurring outside their usual locations are exceptionally rare, exhibiting atypical imaging characteristics, including unusual signal intensities on T1- and T2-weighted MRI sequences, along with the absence of the typical pattern of complete restricted diffusion. These findings may be indicative of a mixture of blood products and proteinaceous substances within the cyst. Subsequently, it may be misdiagnosed as other intracranial pathologies.
Keywords: Atypical, Case report, Epidermoid cyst, Intradiploic
INTRODUCTION
Epidermoid cysts are benign, slow-growing, extra-axial tumors that represent approximately 1% of all intracranial tumors.[
In contrast, epidermoid cysts occurring in intradiploic or intraparenchymal sites are exceedingly rare, accounting for <5% of all intracranial epidermoid cysts.[
Here, we present an atypical case of intradiploic epidermoid cyst, which may be misdiagnosed as other intracranial pathologies, including arachnoid cyst, dermoid, neuroenteric cyst, abscess, and skull metastasis.
CASE DESCRIPTION
A 44-year-old male presented with complaints of a dull, aching headache, predominantly in the frontal region. In addition, the patient noted slowly-growing swelling in the right frontal area of the head. The symptoms had been progressively worsening over the past several months. There was no history of trauma or other neurological symptoms such as seizures, weakness, or sensory changes. The patient’s general medical history was unremarkable, and there was no significant family history of neurological conditions. On examination, the patient had a hard swelling over the right frontal region above the orbit. The swelling was non-tender and immobile, with the scalp moving over the swelling. Neurological examination was unremarkable. A non-enhanced axial computed tomography (CT) brain [
Preoperative magnetic resonance imaging (MRI) brain without and with gadolinium [
Figure 2:
Magnetic resonance imaging brain axial cuts (a) T1-weighted image (T1W1), (b) T2WI, (c) diffusion-weighted imaging (DWI), (d) susceptibility-weighted imaging, and (e) T1WI with contrast showing right frontal non-enhancing lesion corresponds to the expansile intradiploic lytic lesion. The lesion demonstrates heterogeneous T1 and T2 signal intensities with elements of diffusion restrictions in DWI and variable intrinsic T1 hyperintense signal changes, which might reflect a combination of blood products and proteinaceous materials. In addition, susceptibility weighted imaging (SWI) demonstrated blooming artifacts, which suggested the presence of blood products within the lesion.
Both CT and MRI findings favored a diagnosis of a right frontal extra-axial lesion, with radiological features consistent with an intradiploic hemorrhagic epidermoid; however, other differentials considered were arachnoid cyst, dermoid, neuroenteric cyst, abscess, and skull metastasis.
The patient underwent right frontal craniotomy and excision of the lesion. Intraoperatively, the cyst was in the bone, causing thinning and invasion of the overlying dura [
The histopathological examination of the excised tissue confirmed the diagnosis of an intradiploic epidermoid cyst. The tissue consisted of irregular, soft, gray-white pieces measuring 6 × 4 × 1.5 cm. Microscopic examination revealed typical features of an epidermoid cyst, including the presence of cholesterol clefts and chronic inflammation [
Figure 5:
Hematoxylin and eosin-stained slide (a) ×20 shows a cyst wall lined by squamous epithelium containing flaky keratin, with no associated adnexal structures or endodermal/mesodermal tissues, and (b) ×10 shows extensive mixed inflammation with lymphocytes and hemosiderin-laden macrophages, along with cholesterol clefts of varying sizes.
DISCUSSION
Atypical epidermoid cysts are rare, extra-axial lesions constituting <1.5% of all intracranial epidermoid cysts.[
Intradiploic epidermoid cysts (including congenital cholesteatomas) account for approximately 3% of the above group.[
Intradiploic epidermoid cysts arise from aberrant ectodermal remnants trapped after neural tube closure compared to intraparenchymal epidermoid cysts, which are believed to result from ectodermal inclusion occurring before the 3rd week of embryogenesis, during the formation of the primary cerebral vesicle.[
Thus far, few series of atypical epidermoid cysts have been reported due to the low incidence of epidermoid cysts, especially those with atypical MRI appearance.
CT brain for the typical intradiploic epidermoid cysts includes a non-enhancing hypodense lesion with sharply demarcated bony defects and zones of calcifications that may alter the outer and/or inner tables of the skull,[
A study by Ren et al.[
The elevated protein content within the cyst, which led to significant heterogenous signals in both T1- and T2-weighted MRI, also contributed to the absence of the classic pattern of complete restricted diffusion within the whole lesion.[
Given the characteristics of our case, it could be mistaken for other lesions. In a study by Ren et al.[
Complete resection of epidermoid cysts provides a definitive treatment, effectively preventing recurrence or complications such as aseptic meningitis.[
CONCLUSION
Atypical intradiploic epidermoid cysts are extremely rare and display unusual imaging features, such as atypical signal intensities on T1- and T2-weighted MRI brain and the lack of the usual pattern of complete restricted diffusion. These characteristics could suggest the presence of a combination of blood products and protein-rich material within the cyst. As a result, the cyst may be mistakenly diagnosed as another type of intracranial pathology.
Ethical approval:
The Institutional Review Board approval is not required.
Declaration of patient consent:
Patient’s consent not required as patients identity is not disclosed or compromised.
Financial support and sponsorship:
Nil.
Conflicts of interest:
There are no conflicts of interest.
Use of artificial intelligence (AI)-assisted technology for manuscript preparation:
The authors confirm that there was no use of artificial intelligence (AI)-assisted technology for assisting in the writing or editing of the manuscript and no images were manipulated using AI.
Disclaimer
The views and opinions expressed in this article are those of the authors and do not necessarily reflect the official policy or position of the Journal or its management. The information contained in this article should not be considered to be medical advice; patients should consult their own physicians for advice as to their specific medical needs.
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