The study aimed to demonstrate rapid and effective molecular testing on liquid-based cytology (LBC) samples for EGFR, KRAS and BRAF mutations using the Biocartis Idylla™. Rapid on-site evaluation (ROSE) LBC samples for patients with non-small cell lung carcinoma (NSCLC) or pancreatic ductal adenocarcinoma (PDAC) were tested for EGFR, KRAS and BRAF mutations based on the relevance to tumour subtype. The quantification values (Cq values) and mutation detection status were compared between LBC samples and routine formalin-fixed paraffin-embedded (FFPE) clot samples. ROSE LBC samples (n = 54) showed a higher yield of well-preserved tumour and wild type (WT) DNA, demonstrated by lower quantification cycles, no false positives or false negatives, and a higher sensitivity for low allele frequency mutations when compared with FFPE clot samples. The Biocartis Idylla™ provides highly sensitive, reliable and rapid testing for LBC samples for the detection of EFGR and KRAS mutations. BRAF mutations were not detected in the participant cohort; however, all LBC WT BRAF results correlated with the results from the FFPE clot samples. Access to rapid molecular testing using LBC samples can detect the most frequent driver mutations closer to the time of diagnosis, enabling the selection of the most effective first-line targeted therapy sooner, reducing delays or side effects from suboptimal treatments, patient anxiety and costs to healthcare systems, whilst improving patient outcomes.

Background: This invited review for the special issue is a celebration of the continued growth of knowledge in the field of serous fluid cytopathology. Summary: The review begins by addressing the value of cytological examination of the fluid samples in conjunction with clinical, radiological and biochemical data interpreted by the treating physician. It then covers the advances in cytopreparatory techniques with special reference to existing and emerging ancillary techniques available to obtain maximal diagnostic, prognostic & therapeutic information for the practice of precision medicine. The concept of mesothelioma as a cytological diagnosis has been made possible in recent years through clinical research and advocacy by experts and this has added value to serous fluid samples especially when this is the only sampling method available for a patient. Advances in the recommended repertoire of immunostains and a standardised approach through the use of diagnostic categories has been made possible by the International system for reporting serous fluid cytopathology. The reporting system has found application to other types of fluid samples, most recently, cerebrospinal fluid cytology which will be included in the forthcoming edition of the terminology system and is introduced in this special issue. Key messages. The review charts a journey commemorating important landmarks in our current understanding of serous fluids in diagnostic cytopathology.