In this issue, we talk about another branch of pathology, cytopathology. Cytopathology, also known as clinical cytology, is a discipline that diagnoses disease by observing changes in cellular morphology. Determining disease by observing cell morphology began in 1838 when Miller first observed morphological changes in cells taken from tumor tissue under the microscope. Later, Beale, Sanders and Dufour discovered cancer cells in sputum, urine and cerebrospinal fluid, respectively. 1954 Papanicolaou edited Atlas of Exfoliative Cytology, which made cytology a real discipline. 1961 Koss wrote Diagnostic Cytology and its Pathological Basis, which brought cytology and pathology closely together and It gradually developed into an important branch of pathology, DD cytopathology (Cytopathology). The most important application of cytopathology is the diagnosis of tumors, i.e., the presence or absence of tumor cells in cytology specimens such as sputum, urine, chest and abdominal fluid, cervical smear and needle aspiration, and the type of tumor cells if the cell morphology is typical. Therefore, cytopathology can be used for tumor screening, that is, to screen out cancer and precancerous lesions in healthy people through appropriate methods and diagnosis, so as to achieve the purpose of tumor prevention. In the Yellow Emperor’s Classic of Internal Medicine more than two thousand years ago, there is a saying that “the superior doctor treats the untreated disease”, which means that the person who is highly skilled in medicine (superior doctor) is the one who can prevent the disease. An example of its successful application is cervical cancer cytology screening, i.e., the detection of cervical cancer and precancerous lesions by observation of cervical exfoliated cells, which has significantly reduced the incidence and mortality of cervical cancer worldwide since its application. It also plays an important role in lung cancer screening (sputum cytology) and esophageal cancer screening (esophageal pull-down and esophageal brush smear cytology). Cytopathology can also provide a diagnostic basis for the treatment of tumor patients who require preoperative radiotherapy or chemotherapy or those with chest and abdominal fluid onset; it can also be conveniently used for follow-up observation after tumor treatment, such as determining whether there is recurrence through the diagnosis of cervical smear after cervical cancer treatment, and determining whether there is recurrence through needle aspiration cytology diagnosis of chest wall nodules after breast cancer surgery. In addition, cytopathology can also diagnose certain benign lesions, such as pathogenic bacteria and related cytopathological changes found in specimens of infectious diseases (tuberculosis, mycobacteria, etc.). In contrast to histopathology, cytopathology is the study of cytological specimens that can be derived from almost all tissues and organs of the body. Depending on the type of specimen, it can be divided into two major parts: exfoliative cytology and pinprick cytology. Exfoliative cytology specimens are spontaneously shed cells or exfoliated cells obtained by scraping, brushing or flushing methods, including plasma membrane cavity fluid (pleural fluid, ascites, pericardial fluid, cerebrospinal fluid), thoracic or abdominal flush fluid, cervical smear, urine, sputum, endoscopic brushings (esophageal brushings, tracheal brushings, gastric brushings, intestinal brushings), alveolar lavage fluid, papillary overflow, papillary scrapings, and secretion smears. It is required that the specimens be sent for examination as soon as possible after sampling to prevent cell degeneration. Different specimens also have special requirements, such as pleural fluid, ascites, pericardial fluid specimens require more than 100ml to be sent for examination (special cases such as encapsulated fluid can also be in smaller amounts), add anticoagulant (heparin or citrate), place in a clean and dry container and send for examination as soon as possible. If the specimen cannot be sent for examination in time under special circumstances, it should be refrigerated at 4°C. Sputum specimens should be routinely sent three times to improve the detection rate, and generally require a second mouthful of sputum to be left in the morning after gargling and placed in a sputum box or sputum tube for testing as soon as possible. Needle aspiration cytology specimens are cells aspirated through puncture needles, including needle aspiration of body surface masses such as lymph nodes, ultrasound or CT-guided needle aspiration specimens and endoscopic needle aspiration specimens, which can be taken from a wide range of organs throughout the body. According to the inner diameter of the puncture needle, there are fine needle aspiration (inner diameter less than 0.9mm) and coarse needle aspiration (inner diameter greater than 0.9mm) specimens. Needle aspiration cytology has its indications: deep lesions, surgical sampling is difficult or too costly; surgical sampling will interfere with subsequent treatment; there is a risk of local or systemic spread of lesions through surgical wounds; surgical procedures have the risk of causing hemorrhage or infection; the patient’s health condition is not suitable for surgical procedures; patients or family members refuse to accept surgical procedures, etc. Patients with bleeding tendency, suspected vascular lesions (such as arteriovenous malformations, hemangiomas, etc.), patients with suspected cysticercosis, etc. are contraindicated to do coarse needle aspiration; patients with severe pulmonary insufficiency (such as emphysema, pulmonary hypertensive heart disease, severe hypoxemia) and patients with uncontrollable cough are contraindicated to do thoracic needle aspiration; patients who cannot cooperate, are overly sensitive and have too much concern also try to avoid needle aspiration. Needle aspiration can also have complications such as a small amount of bleeding, thyroid needle aspiration may occasionally result in injury to the recurrent laryngeal nerve (rare), thyroid cysts and isthmus lesions may occasionally result in transient toxicity, chest wall lesions may occasionally result in pneumothorax, and a very small number of patients may experience a vasoneurotic reaction after needle aspiration resulting in mild headache or even fainting (commonly known as dizziness). Complications of needle aspiration in deeper lesions are more frequent and relatively serious, such as internal bleeding, pneumothorax, infection, etc., but life-threatening cases are rare. Will the tumor metastasize along the needle tract? This is a question that most people are concerned and doubtful about. On this point, a lot of studies have been conducted at home and abroad, and tens of thousands of cases of fine needle aspiration have accumulated clinical follow-up data, and no metastasis has been seen. The risk of 0.4% for coarse needle aspiration biopsy has been reported in the literature, but when the cytologic or histopathologic diagnosis is malignant, there is usually a standardized follow-up treatment for the lesion such as surgical excision, radiation therapy or chemotherapy. Most cytopathology specimens can be smear directly, some specimens still require pre-processing, such as plasma cavity fluid and urine specimens need to be centrifuged to take precipitate before smear preparation. In the last decade or so, a new filming technique, ThinlayerCellTest (TCT), has emerged, which is a computerized chip-controlled programmed filming with uniform, thin smears and can preserve almost all specimens obtained on the sampler, greatly reducing the coverage of blood, mucus and inflammatory cells on the It also facilitates the development and quality control of ancillary diagnostic techniques such as immunohistochemical examination. Regardless of the method of smear preparation should be immediately fixed in 95% ethanol, otherwise the cells will degenerate and affect the diagnosis. Then HE or Pap staining is performed, the smear is sealed, and the cytopathologist reads the smear to make a diagnosis. In decidual cytology specimens, abnormal cells are scattered in varying numbers in the background of cells at the original site (e.g., cancer cells in cancerous thoracic and abdominal waters are scattered in the background of a large number of mesothelial cells in the thoracic or abdominal cavity), which may make diagnosis difficult when the number of abnormal cells is small or the morphology is atypical, or when the background abnormalities mask the cell morphology. Needle aspiration cytology specimens, on the other hand, can be viewed as tiny biopsies composed of individual cells and cell populations, but are more limited than the small specimen sampling we described in the previous issue. Most cytopathology specimens are available in about 24 hours, and in emergency situations, such as intraoperative thoracic and abdominal irrigation fluid, in about 30 minutes. In a few cases, molecular biology and immunohistochemistry tests are also needed to assist in the diagnosis, which may take about a week to produce results. Through the above introduction, we know that cytopathology is easy to perform, convenient and fast, with little or no damage to the patient, and can be repeatedly performed at relatively low cost. However, cytopathology specimens also have their inherent drawbacks – the lesion is limited, the cells are scattered, and the tissue structure of the lesion cannot be seen, nor can the adjoining relationships be seen (histopathology has the advantage of this). Therefore, the diagnosis of cytopathology may be uncertain, such as “suspicious cancer”, “not excluding malignancy”, “further examination is recommended to exclude malignancy”, etc., and sometimes it is necessary to retrieve the material again or do auxiliary tests such as immunohistochemistry. In some cases, it is necessary to retrieve the material again or do auxiliary tests such as immunohistochemistry. Cytopathology and histopathology can complement and corroborate each other. Some lesions cannot be biopsied for histopathological examination, such as plasma cavity effusion without primary foci, lesions without clear occupancy, lung cancer in small bronchi, etc., which usually require cytopathology to determine the nature of the lesion before proceeding to the next step of treatment; cytopathological examination is convenient and quick, with little or no damage, and is more suitable than histopathology for tumor screening and follow-up of tumor patients after treatment. The cytopathological examination is convenient and quick, with little or no damage. In contrast, histopathology specimens have tissue structures that are not available in cytopathology specimens, and the diagnosis is often more certain; lesions detected by cytology screening often require further confirmation by histopathology. Since the establishment of the first cytology laboratories in China by Professor Yang Dawang in the early 1950s, cytopathology has made great development in China, but there is still a gap compared with developed countries. We know that cytopathology has unique advantages in tumor screening, but our medical system is not sound and our people have little awareness of health care, so they often seek medical treatment only after they get sick, which to a certain extent has caused our medicine to be in the state of “lower medicine” (from “Huangdi Neijing”: “lower medicine treats On the other hand, cellular pathology has not been taken seriously. However, with the deepening of medical reform, the application of new technologies and the change of people’s health consciousness, our medicine will be developed rapidly, and cytopathology will also have a great development.