Comparison between cytospin and liquid-based cytology in cerebrospinal fluid diagnosis of neoplastic diseases: A single institution experience.

OBJECTIVE: The current tools available for detecting malignant neoplasms in the cerebrospinal fluid (CSF) are neurological examination, followed by neuroimaging, cytology and molecular techniques. To highlight the role of cytology the diagnosis of metastatic tumours in CSF samples, we present our experience using cytospin and ThinPrep liquid-based cytology. METHODS: A retrospective analysis was conducted using the pathological records of 8181 cytological specimens of CSF, which were diagnosed over a 17-year period. Between 2000 and 2014, a total of 6994 CSF samples were processed using cytospin method and 1187 specimens were examined using ThinPrep method in the period between 2015 and 2017. RESULTS: The most frequent metastatic neoplasm of the first period was non-Hodgkin lymphoma; in the second period the commonest malignancy found was brain tumour (glioblastoma and medulloblastoma). The samples processed by cytospin revealed cytolysis and haemorrhage, while the cases processed by ThinPrep had a clear background. Ten false-positive cases belonging to the suspicious category were processed by cytospin, while there was only one false positive case in the group processed by ThinPrep. The positive predictive value was 95% in cytospin and 100% in Thin Prep with comparable sensitivity, specificity, diagnostic accuracy and negative predictive values. CONCLUSIONS: CSF cytology is a reliable technique for identifying malignancy in CSF. ThinPrep technology can be applied with good results in terms of clear background, cell enrichment, better nuclear details and high cellularity per slide.