[Malignant transformation of epidermoid cyst]

The paper presents a rare case of malignant transformation of an epidermoid cyst to the keratinizing type of squamous cell carcinoma. In a 47-year-old female patient with severe visual disturbances, MRI scans revealed a large supracellular tumor spreading to the third ventricle and medial portions of temporal lobes. The tumor was removed. A histological study of its biopsy specimen showed signs of both a benign process (epidermoid cysts) and its malignant epidermoid degeneration to the keratinizing type of squamous cell carcinoma. After 12-month combined therapy there was a continuous tumor growth with a significant dissemination within the base of the skull. The pathogenesis of epidermoid cysts, possible causes of malignant transformation, modalities of treatment and prognosis are briefly discussed.