Cytological preparations for molecular analysis: A review of technical procedures, advantages and limitations for referring samples for testing

Minimally invasive procedures such as endobronchial ultrasound‐guided transbronchial needle aspiration (EBUS‐TBNA) must yield not only good quality and quantity of material for morphological assessment, but also an adequate sample for analysis of molecular markers to guide patients to appropriate targeted therapies. In this context, cytopathologists worldwide should be familiar with minimum requirements for refereeing cytological samples for testing. The present manuscript is a review with comprehensive description of the content of the workshop entitled Cytological preparations for molecular analysis: pre‐analytical issues for EBUS TBNA, presented at the 40th European Congress of Cytopathology in Liverpool, UK. The present review emphasises the advantages and limitations of different types of cytology substrates used for molecular analysis such as archival smears, liquid‐based preparations, archival cytospin preparations and FTA (Flinders Technology Associates) cards, as well as their technical requirements/features. These various types of cytological specimens can be successfully used for an extensive array of molecular studies, but the quality and quantity of extracted nucleic acids rely directly on adequate pre‐analytical assessment of those samples. In this setting, cytopathologists must not only be familiar with the different types of specimens and associated technical procedures, but also correctly handle the material provided by minimally invasive procedures, ensuring that there is sufficient amount of material for a precise diagnosis and correct management of the patient through personalised care. The success of molecular analysis lies in the optimum quality of the genetic material that may be obtained from smears, cytospin preparations, liquid‐based cytology and cell blocks. Each of these procedures has advantages and drawbacks in terms of efficacy, costs, standardization and infrastructure requirements. The structure of this review includes those cytology substrates and discusses their use for molecular analysis, explores the technical procedures (or requirements) that can be employed to achieve adequate DNA recovery and provides an analysis of their advantages and limitations.