Cerebellopontine Angle Epidermoid Cyst With a Focal White Component and Target-Like Appearance: A Case Report

Intracranial epidermoid cysts typically exhibit cerebrospinal fluid-like signal intensity on magnetic resonance imaging (MRI), whereas white epidermoid cysts display atypical imaging characteristics, particularly intrinsic T1 hyperintensity.We report the case of a 64-year-old woman with progressive leftsided tinnitus and hearing loss, in whom an extra-axial lesion was identified in the left cerebellopontine angle.MRI demonstrated a predominantly T1-hypointense lesion with a central punctate hyperintense focus surrounded by a hypointense rim, creating a distinctive target-like appearance.The lesion showed no significant contrast enhancement and demonstrated true diffusion restriction.Surgical resection revealed a pearly, avascular cyst containing thick, whitish keratinous material.Histopathologic examination revealed a cyst lined by keratinizing stratified squamous epithelium, containing abundant lamellated keratin, compact keratin with a mosaic-like appearance, and focal amorphous eosinophilic material, confirming the diagnosis of an epidermoid cyst.The focal T1 hyperintensity may represent a localized manifestation of the white epidermoid phenotype, although this association remains hypothetical in the absence of biochemical characterization of the cyst contents.This case expands the recognized imaging spectrum of intracranial epidermoid cysts and highlights the importance of integrating radiologic, surgical, and histopathologic findings when evaluating atypical cerebellopontine angle lesions.