Recurrent epidermoid cyst with malignant transformation into squamous cell carcinoma.

A 50-year-old male presented with a recurrent epidermoid cyst with malignant transformation into squamous cell carcinoma. The patient was first hospitalized for intermittent seizures in 2000. Computed tomography (CT) showed a hypodense lesion with enhanced capsule but no peripheral edema in the right temporal lobe. Craniotomy was performed and the lesion was completely removed. The histological diagnosis was epidermoid cyst. Six years later, the patient experienced blurred vision and hemiparesis in the left extremities. CT showed a hyperdense mass with peripheral edema in the right temporal lobe. Repeat CT 2 months later revealed a larger mass. The recurrent lesion was removed, and the histological diagnosis was squamous cell carcinoma. Intracranial epidermoid cyst is a benign tumor which often appears hypodense on CT, so change to hyperdensity in the recurrent tumor may indicate malignant transformation.