Concurrent occurrence of squamous cell carcinoma in a cerebellopontine angle epidermoid cyst: A case report and review of the literature

BACKGROUND: Intracranial epidermoid cysts are rare benign lesions. Cases of malignant transformation (MT) into squamous cell carcinoma (SCC) have rarely been reported. We present a case of concurrent occurrence of SCC diagnosed during primary resection of epidermoid cyst (EC) and a relevant literature review. CASE DESCRIPTION: A 61-year-old patient was diagnosed with a right cerebellopontine angle (CPA) lesion after suffering from vertigo, diplopia, and right trigeminal (V2) hypoesthesia. Brain magnetic resonance imaging (MRI) showed a lesion consistent with an EC, demonstrating restricted diffusion with rim-enhancing area on the medial side of the cyst. During resection, two different tissue pathologies were observed, one consistent with an epidermoid (which was completely removed) and an additional firm tissue adherent to the brainstem, preventing gross total resection. Pathological evaluation confirmed two separate histologies – epidermoid and SCC. The patient never recurred to complete the recommended radiotherapy. Eleven months following surgical resection, a follow-up MRI showed local massive recurrence of the enhancing lesion. He was, further, treated with radiotherapy and is currently being followed up. CONCLUSION: MT of an intracranial EC to SCC is rare and associated with poor prognosis. SCC may be found incidentally at time of primary resection or arise from a remnant of previously operated EC. Thus, aggressive complete resection should be intended, and separate pathological specimens should be sent from any abnormal region of the tumor.