[A case of meningeal melanomatosis diagnosed by immunostaining of cerebrospinal fluid].

A 49-year-old woman was admitted to our hospital with suspected hypertensive encephalopathy. On the basis of MRI showing leptomeningeal enhancement and Class V cytology of the CSF, she was diagnosed as having leptomeningeal carcinomatosis. Although no primary site was detected, a few melanin granules were observed at the third CSF examination. The atypical cells in the CSF demonstrated immunoreactivity for HMB-45 and S-100, which are specific markers of malignant melanoma. There have been few reports of meningeal melanomatosis in Japan. This case illustrates that immunostaining is diagnostically useful in patients with leptomeningeal carcinomatosis from neoplasms with unknown primary sites.