[Tips and tricks for the cytological management of cysts]

Fine needle aspiration is a well-known procedure for the diagnosis and management of solid lesions. The approach to cystic lesions on fine needle-aspiration is becoming a popular diagnostic tool due to the increased availability of high-quality cross-sectional imaging such as computed tomography and ultrasound guided procedures like endoscopic ultrasound. Cystic lesions are closed cavities containing liquid, sometimes partially solid with various internal neoplastic and non-neoplastic components. The most frequently punctured cysts are in the neck (thyroid and salivary glands), mediastinum, breast and abdomen (pancreas and liver). The diagnostic accuracy of cytological cyst sampling is highly dependent on laboratory material management. This review highlights how to approach the main features of superficial and deep organ cysts using basic cytological techniques (direct smears, cytocentrifugation), liquid-based cytology and cell block. We show the role of a multimodal approach that can lead to a wider implementation of ancillary tests (biochemical, immunocytochemical and molecular) to improve diagnostic accuracy and clinical management of patients with cystic lesions. In the near future, artificial intelligence models will offer detection, classification and prediction capabilities for various cystic lesions. Two examples in pancreatic and thyroid cytopathology are particularly developed.