Malignant transformation of an intracranial epidermoid cyst into squamous cell carcinoma: a case report and systematic review

Objective Intracranial epidermoid cysts (IECs) are rare, benign congenital lesions that occasionally undergo malignant transformation into squamous cell carcinoma (SCC). This study presents a rare case of an IEC in the anterior cranial fossa transforming into SCC and reviews existing literature to summarize clinical characteristics, treatment strategies, and survival outcomes. Methods We detail the clinical presentation, management and long-term follow-up of a 52-year-old female who developed SCC 75 months after initial subtotal resection of an anterior cranial fossa IEC. We also conducted a comprehensive systematic literature search across PubMed, MEDLINE and CNKI in accordance with PRISMA guidelines compiling 59 well-documented cases (including our index case) to analyze demographic features, transformation intervals, treatment modalities and overall survival. Results Our patient underwent repeat subtotal tumor resection followed by adjuvant intensity-modulated radiation therapy (IMRT). She maintained a disease-free survival (DFS) of 14 months post-radiotherapy (17 months post-reoperation) until July 2026, when she developed multifocal intraventricular recurrence. The literature review revealed a mean patient age of 54.7 years with an equal gender distribution (1.03:1). The cerebellopontine angle (CPA) was the most frequent tumor site (50.85%). The mean interval from IEC diagnosis to malignant transformation was 9.24 years. Prognosis for transformed SCC remains poor, with a median overall survival of 6 months. However, patients treated with surgery combined with radiotherapy demonstrated significantly improved outcomes (median survival 13 months) compared to those undergoing surgery alone (41 days). Conclusions Malignant transformation of IECs into SCC is a rare, aggressive complication. Long-term surveillance with contrast-enhanced MRI is vital for patients with previously resected IECs. Early detection, maximal safe surgical resection followed by adjuvant radiotherapy currently offers the most favorable survival benefit.