Atypical Intra-diploic Epidermoid Cyst: A Case Report

Background Intra-diploic epidermoid cysts of the skull are rare, benign lesions, with fewer than 100 reported cases. These cysts typically present as expansile bone lesions but can exhibit atypical imaging featuresthat may complicate diagnosis. Case Presentation We describe a case of a 30-year-old womanwho presented with right-sided tinnitus, earache, and a palpable peri-auricular mass. High-resolution computed tomography and magnetic resonance imaging demonstrated a cystic lesion within the right temporal bone, extending into the cerebellopontine angle, jugular foramen, and external auditory canal. The lesion caused lytic destruction of adjacent bony structuresand exhibited peripheral contrast enhancement without restricted diffusion, which is atypical for epidermoid cysts. Histopathological examination confirmed an intra-diploic epidermoid cyst. Conclusion This case highlights the radiological variability of intra-diploic epidermoid cysts, particularly the potential for enhancement and absence of diffusion restriction, which can mimic more aggressive pathologies. Radiologists should consider epidermoid cysts in the differential diagnosis of cerebellopontine angle masses, especially when encountering lesions with bone destruction and atypical enhancement patterns.