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Year : 2018  |  Volume : 4  |  Issue : 1  |  Page : 68-70

Rare case of atypical intraparenchymal epidermoid cyst

1 Department of Neurosurgery, Bangalore Medical College and Research Institute, Bengaluru, Karnataka, India
2 Department of General Surgery, Bangalore Medical College and Research Institute, Bengaluru, Karnataka, India
3 Department of Neuropathology, National Institute of Mental Health and Neurosciences, Bengaluru, Karnataka, India

Date of Submission02-Mar-2018
Date of Acceptance07-Mar-2018
Date of Web Publication25-May-2018

Correspondence Address:
Nagarjun Maulyavantham Nagaraj
No 6, Akshaya, 1st B Cross, Byrasandra, Jayanagar 1st Block East, Bengaluru - 560 011, Karnataka
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jcrsm.jcrsm_7_18

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Epidermoids are extra-axial brain lesions seen mostly in the cerebellopontine angle with typical imaging characteristics. We present a case of the right frontal intraparenchymal epidermoid cyst with atypical magnetic resonance imaging features. This case report is to highlight the rarity of location and atypical radiological feature.

Keywords: Calcified epidermoid, frontal epidermoid, intraparenchymal epidermoid

How to cite this article:
Nagaraj NM, Bysani PR, Dutta S, Nagesh S A, Nandeesh BN, Pai BS. Rare case of atypical intraparenchymal epidermoid cyst. J Curr Res Sci Med 2018;4:68-70

How to cite this URL:
Nagaraj NM, Bysani PR, Dutta S, Nagesh S A, Nandeesh BN, Pai BS. Rare case of atypical intraparenchymal epidermoid cyst. J Curr Res Sci Med [serial online] 2018 [cited 2022 Nov 29];4:68-70. Available from: https://www.jcrsmed.org/text.asp?2018/4/1/68/233206

  Introduction Top

Epidermoids are benign extra-axial lesions seen most commonly in cerebellopontine (CP) angle with typical imaging characteristics. Intraparenchymal epidermoids are rare, and only a few cases of frontal intraparenchymal epidermoids are reported.

  Case Report Top

A 34-year-old gentleman presented with three episodes of generalized tonic–clonic seizures over 6 months with occasional frontal headache. His neurological examination was unremarkable and fundus was normal.

Computed tomography (CT) scan of the head showed right frontal predominantly hypodense lesion with subfalcine extension to the opposite side, mass effect on both frontal horns. The lesion had dense calcification extending up to the dura. On magnetic resonance imaging (MRI), lesion was heterogeneous with hypointense to isointense on T1-weighted images, hyperintense to isointense on T2-weighted images with a thin rim of enhancement on contrast with no perilesional edema. Diffusion restriction was noted, and fluid-attenuated inversion recovery (FLAIR) showed hyperintensity in noncalcific areas [Figure 1].
Figure 1: Imaging of the patient shows hypodense lesion with calcification and subfalcine extension on computed tomography scan (a), heterogeneously hypointense on T1-weighted sequence (b), predominantly hyperintense on T2-weighted images axial and coronal sequence, respectively (c and d), hyperintense on fluid-attenuated inversion recovery (e), peripheral thin ring enhancement on contrast (f), few areas of restriction on diffusion (g), and gradient (h) sequences. Postoperative computed tomography shows total excision (i) and same is seen in T2-weighted image of follow-up magnetic resonance imaging after 4 months of surgery (j)

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Provisional diagnosis of low-grade oligodendroglioma was thought in view of clinical presentation, apparent intraparenchymal location, dense calcification, heterogeneity, and absence of edema. Intraoperatively, tumor was adherent to dura and pia with clear tumor–brain interface in some areas. The lesion was pearly white to yellow, avascular with areas of calcification. Total excision was possible without any deficits. He is seizure free till recent follow-up of 1 year.

Histopathology showed stratified squamous epithelium-lined cyst containing lamellated keratinous material with dense calcification. The wall showed chronic inflammatory infiltrate adherent to adjacent brain parenchyma which had reactive changes favoring a diagnosis of infected epidermoid cyst possibly secondary to rupture of cyst contents [Figure 2].
Figure 2: Histology of the patient showing keratinizing stratified squamous epithelium-lined cyst wall with laminated keratin filling the cavity. There is adjacent zone inflammation (a). (b) Laminated keratin contents with calcification (×200)

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  Discussion Top

Epidermoids are extra-axial slow-growing benign lesions accounting for 0.2%–1.8% of intracranial tumors. They arise due to secondary disruption of neural tube closure, during the 3rd to 5th week of gestation. They are seen most commonly in the CP angle followed by parasellar region but can also be found in the pineal region, ventricles, Sylvian fissure, and interhemispheric fissures.

Controversy exists regarding the pathogenesis of intraparenchymal epidermoid. It is hypothesized that there may be sequestration of cutaneous ectoderm into the closing neural tube between the 3rd and 5th weeks of gestation. If the sequestration occurs early and on the inner surface of the neural tube, intraparenchymal epidermoids are formed.[1] In our case too, we feel that the epidermoid is intraparenchymal with the above pathogenesis. On CT, they are typically uniformly hypodense with no contrast enhancement, and on MRI, they are typically T1 hypointense, T2 hyperintense with no or ring enhancement seen on contrast. Hyperintensity on FLAIR and Constructive Interference in Steady State (CISS) sequences, characteristic restriction in Diffusion and Apparent Diffusion Coefficient (ADC) images help in differentiating it from other cystic lesions like arachnoid cysts. The diffusion restriction of epidermoids is a characteristic feature differentiating it from arachnoid cysts. About 5%–6% have unusual locations and atypical radiological features.[2] Less than 1% of epidermoids are intraparenchymal.[3] Intraparenchymal epidermoids are known to have atypical imaging features such as calcification on CT, isointense or hyperintense on T1, heterogeneous on T2 and FLAIR, and heterogeneous restriction on DWI.[3] White epidermoids are a variant of epidermoids which have hyperintense signal intensity on T1- and T2-weighted images due to high lipid contents (and some epidermoids may have hyperdensities on plain CT due to high protein contents).

The imaging in our patient showed atypical imaging features. The lesion appeared intraparenchymal and did not have a clear plane from the adjacent frontal lobe in both CT and MRI. There was subfalcine extension to opposite side like a corpus callosal glioma. Plain CT scan showed hyperdensities suggestive of calcification. There was heterointensity in all MRI sequences. Even though there were areas of T1 hypointensity, they were hyperintense to cerebrospinal fluid.

All these features were suggestive of an intraparenchymal tumor, probably an oligodendroglioma in view of calcification.

Careful analysis of imaging characteristics helps differentiate this lesion from oligodendroglioma. Restriction on diffusion, failure of inversion on FLAIR, and dense calcification are some of the features favoring an epidermoid over oligodendroglioma.

A combination of atypical MRI findings and rarity of the location of this tumor make this case report unique with only five cases of frontal intraparenchymal epidermoids having atypical radiological features reported in literature.[2] They can easily be misdiagnosed.

Epidermoids are generally benign and very rarely transform into squamous cell carcinoma. Complete excision is the definitive treatment, and in cases where the capsule is densely adherent to vital structures, leaving behind a part of the capsule is justified and safe. Recurrences are rare.

  Conclusion Top

Epidermoid needs to be considered in the differential diagnosis of intraparenchymal lesions with atypical MRI findings.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

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Conflicts of interest

There are no conflicts of interest.

  References Top

Kaido T, Okazaki A, Kurokawa S, Tsukamoto M. Pathogenesis of intraparenchymal epidermoid cyst in the brain: A case report and review of the literature. Surg Neurol 2003;59:211-6.  Back to cited text no. 1
Sarkar H, Vijaya G, Mitta S. Rare occurrence of intracranial epidermoid tumor in an unusual location with atypical radiological features. Asian J Neurosurg 2015;10:319-21.  Back to cited text no. 2
[PUBMED]  [Full text]  
Lian K, Schwartz ML, Bilbao J, Perry J, Aviv RI, Symons SP, et al. Rare frontal lobe intraparenchymal epidermoid cyst with atypical imaging. J Clin Neurosci 2012;19:1185-7.  Back to cited text no. 3


  [Figure 1], [Figure 2]

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