Serous fluid cytopathology: landmark developments in techniques, terminology & clinical application

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.