Re-evaluation of cerebrospinal fluid cytology for diagnosis of leptomeningeal metastasis based on radiological features, patient symptoms/signs, and clinical follow-up.

purposeCerebrospinal fluid (CSF) cytology presents challenges in the diagnosis of leptomeningeal metastasis (LM) due to frequent false negatives. We re-evaluated the diagnostic accuracy of CSF cytology with reference to accompanying magnetic resonance imaging (MRI) findings and LM symptoms/signs, incorporating longitudinal follow-up data.

methodsIn total, 697 consecutive CSF samples obtained for LM diagnosis from 234 patients were analyzed. The final determination of LM was made using 3-month follow-up data, considering therapeutic interventions.

resultsConcordance among the three diagnostic factors—CSF cytology, MRI findings, and LM symptoms/signs—was observed in 70% of LM-positive cases and 53% of LM-negative cases. Clinical scenarios with longitudinal data were classified into 13 categories, with final diagnoses of true positive (n = 238, 34.1%), false positive (n = 30, 4.3%), true negative (n = 261, 37.4%), and false negative (n = 168, 24.1%). CSF cytology alone yielded an area under the curve (AUC) of 0.737; the combined three-factor model achieved an AUC of 0.981. Diagnostic evaluation of eight combinations derived from the dichotomized three factors showed that cases concordant for all three factors had a 100% positive predictive value (PPV) and 97.8% negative predictive value. Among discordant cases, LM symptoms/signs demonstrated the highest predictive value (PPV: 97.1% with negative cytology findings and 100% with negative MRI findings). MRI findings alone showed limited diagnostic value (PPV: 45.3%) when the other two factors were discordant.

conclusionThe relatively high discordance among the three diagnostic factors highlights the need for a new combined diagnostic method for LM that incorporates therapeutic interventions and longitudinal follow-up data.