Leptomeningeal metastasis from an intracranial epidermoid cyst

Epidermoid tumors are benign and constitute 1% of all intracranial tumors. Squamous cell carcinoma (SCC) arising in an epidermoid is rare, and leptomeningeal metastasis (LM) from malignant degeneration of an epidermoid is even less common; we have identified only three such patients in the literature.1-3⇓⇓ Demonstration of cancer cells in the CSF is the diagnostic “gold standard” for LM. Sensitivity of a single test is 50 to 60%, but improves to 85% with repeated testing.4 Typical findings on MRI scan can establish the diagnosis of LM without CSF cytology, but only in patients with a known cancer. CSF tumor marker analysis may improve diagnostic sensitivity.5,6⇓ We report a patient who developed LM from malignant degeneration of an epidermoid cyst, had elevated CSF tumor markers, and had persistently negative CSF cytology. A 53-year-old man presented in October 1998 with facial spasms. His neurologic examination was normal. Brain MRI scanning revealed a nonenhancing, cystic mass anterior to the …