Fine needle aspiration cytology is a method of aspirating cells or tissues from certain suspicious lesions on the body with a fine needle for microscopic diagnosis, mainly for neoplastic diagnosis, but also for non-neoplastic diagnosis, such as infectious diseases, metabolic disorders, granulomatous diseases, etc. Fine needle aspiration is used for a wide range of applications, including palpable surface masses, such as thyroid masses, lymph node tissue, breast masses, and subcutaneous masses, as well as deep tissue masses, such as pancreatic, renal, and retroperitoneal masses. Fine needle aspiration cytology is relatively simple, less invasive, generally does not require anesthesia, and the processing time of the specimen is very short, allowing for rapid pathological diagnosis, as well as a high sensitivity and specificity of diagnosis. Fine needle aspiration cytology can be performed not only for cytological morphological observation, but also, if necessary, to make cell blocks for sectioning and staining, and finally to give a diagnosis under the microscope.