White Epidermoid of the Sylvian Fissure Masquerading as a Dermoid Cyst: An Extremely Rare Occurrence

Abstract

We report the case of a 30-year-old female with a Sylvian fissure, white epidermoid which was radiologically looking like a dermoid cyst. The female presented with a headache with no neurological deficits. On radiology, the lesion was in Sylvian fissure, T1 hyperintense, T2 hypointense, and with minimal diffusion restriction medially. Hence a preoperative impression of dermoid cyst was made, a quite uncommon location. Intraoperatively, the classical pearly-white flaky appearance of epidermoid was seen which was confirmed histopathologically. White epidermoids appearing so because of high protein content are a rarity and are more likely to cause aseptic meningitis in the event of intraoperative spillage. Differentiating between a dermoid cyst and white epidermoid preoperatively and radiologically is difficult. Dermoids show diffusion restriction and are usually midline, whereas white epidermoids do not show diffusion restriction and are usually lateral. This is the first report of a white epidermoid in Sylvian fissure to the best of our knowledge.

Keywords: Dermoid cyst; Sylvian fissure; mimicking; white epidermoid.

Figure 1

Preoperative imaging (a and b) shows a well-defined hypodensity in the right Sylvian fissure. Note also the pneumatization of the right anterior clinoid and that of posterior clinoids. (c) Shows a T1-weighted magnetic resonance imaging showing a hyperintense lesion in the right Sylvian fissure which is not causing any mass effect or hydrocephalus. (d) depicts a T2-weighted magnetic resonance imaging in which a well-defined extra axial hypointense lesion can be appreciated with cerebrospinal fluid cleft pushing the right temporal pole posteriorly. (e) Shows that the lesion suppresses on fluid-attenuated inversion recovery. (f) Is a diffusion-weighted imaging showing that the lesion is not showing diffusion restriction except that of a small medial portion of the lesion which is restricted on diffusion-weighted imaging

Figure 2

Postoperative magnetic resonance imaging done at 3 months. (a) Is a T1-weighted imaging showing complete excision of the tumor. (b) Is a T2-weighted imaging showing no residual hypointense mass lesion in the right Sylvian fissure. (c) Is the diffusion-weighted imaging which does not show any obvious evidence of diffusion restriction. (d) Is a clinical postoperative photograph of the patient showing the small frontotemporal incision used to remove the lesion

Figure 3

Histopathology of the tumor showing thin squamous epithelial layer filled with keratinous debris