Malignant transformation of an intracranial large epidermoid cyst with leptomeningeal carcinomatosis: case report.

A 64-year-old female presented with rapid onset of left ophthalmoplegia and truncal ataxia, after experiencing diplopia due to left abducens nerve palsy for a year. She had undergone surgery twice for left trigeminal neuralgia caused by a large intracranial epidermoid cyst at the age of 48 and 52 years. The intracranial epidermoid cyst grew and became predominantly enhanced by contrast medium on computed tomography (CT) and T(1)-weighted magnetic resonance (MR) imaging, which had not been observed earlier. The tumor was partially removed and the histological diagnosis was squamous cell carcinoma (SCC). Radiation therapy was administered, but she presented with paraplegia of the bilateral lower extremities and anesthesia due to spinal multiple metastases of SCC one year later. Radiation therapy was administered for the spinal lesions, but she died of multiple metastases to the cerebellum and medulla oblongata with hydrocephalus 2 years after the third surgery. Transformation of intracranial epidermoid cysts to SCC appears as predominant enhancement on CT or T(1)-weighted MR imaging with rapid deterioration of neurological features. All reported cases of malignant transformation of intracranial epithelial cysts to SCC with leptomeningeal carcinomatosis have occurred in intracranial epidermoid cysts.