DETECTION OF MALIGNANT-CELLS IN CEREBROSPINAL-FLUID USING FLUORESCENCE IN-SITU HYBRIDIZATION

Cytologic examination of cerebrospinal fluid (CSF) is the diagnostic g old standard for leptomeningeal metastasis (LMM). However, this techni que is only moderately sensitive when routine staining procedures are applied. The use of fluorescence in situ hybridization (FISH) to ident ify malignant cells may have an additional value in diagnosing LMM, si nce numerical chromosomal aberrations (NCA) can be detected at the sin gle cell level. We tested the feasibility of FISH to detect tumor cell s in CSF by analyzing 22 samples with proven LMM with a probe for chro mosome 1 (1q12) to detect NCA in the cells. A control group consisted of samples from 10 patients with inflammatory neurologic disease. In 7 LMM samples no cells or only lysed cells were found, due to lime dela y before fixation. Of the other 15 LMM samples analyzed, 13 showed NCA (87%), while no NCA were found in the control group. Our results indi cate that FISH may be a useful additional diagnostic tool to the cytod iagnosis of CSF in cases of LMM. We expect that FISH can become an add itional marker for malignancy at the single cell level in patients wit h LMM, which may also be of use to determine the effect of therapy for LMM.