Leptomeningeal carcinomatosis with normal CSF features.

We report two cases of leptomeningeal carcinomatosis in which CSF-positive cytologic features were present but other CSF measurements were normal--a most unusual combination. In both cases, the results of the cytologic examination led to substantial therapeutic alterations. Cytologic examination of the CSF should be performed in any case with unexplained CNS symptoms or signs, regardless of the character of the CSF.