Although biochemical, immunological and imaging diagnoses of tumors have been greatly developed, pathological diagnosis is still the main way to determine the nature of tumors. Pathological examination is one of the most standard and reliable methods to diagnose tumors, and is the “gold standard” of tumor diagnosis at present. Pathology is usually divided into two major parts: histopathology and cytopathology. It is to take the secretion of the diseased organ or the scraping of the tissue surface to make cytological smear, or to take the section or print of the diseased tissue directly to observe the cell shape and structure under the microscope to determine the nature of the tumor. Pathological diagnosis can not only determine the benignity and malignancy of tumor and its prognosis, but also provide a reliable basis for treatment. However, pathological diagnosis also has limitations. Because the biopsy specimen, specific sampling and sectioning are all sample examinations, what is finally seen under the light microscope is only a very small part of the lesion and sometimes cannot represent the whole lesion. In addition, the reliability of pathological diagnosis is also related to the selection of pathological specimens. Sometimes there are also false negative results. If the clinical diagnosis does not match with the pathological diagnosis, the pathological diagnosis should be reviewed in time, and if the pathological diagnosis is correct, the appropriateness of the selection of the pathological specimen should be considered, and if necessary, the material should be retrieved and the pathological diagnosis should be made again. What are the methods of pathological diagnosis? 1.Exfoliative cytological examination: to take secretions (sputum, papillary overflow), aspirate (chest and ascites), scrapings (vaginal secretions) and urine, etc. and make smears for microscopic examination. It is commonly used for cervical cancer, esophageal cancer, cardia cancer, lung cancer, bladder cancer, breast cancer and cancerous chest and ascites examination. 2.Clamp biopsy: taking small piece of biopsy from the lesion for examination is called biopsy for short. It is taken directly through small surgery or endoscopically as the main means. It is commonly used for skin cancer, nasopharyngeal cancer, oral cancer, esophageal cancer, cardia cancer, gastric cancer, bladder cancer, lung cancer, penile cancer, cervical cancer, colon cancer, rectal cancer or enlarged lymph nodes, etc. 3.Aspiration (fine needle aspiration) biopsy: For large tumors without ulcers and in superficial parts of the body, aspiration biopsy can often be used instead of excisional biopsy, which is simple and easy to perform without complicated processes such as surgical incision and can reduce patient pain. This method is simple and easy to perform, without the complicated process of surgical incision, and can reduce the patient’s pain. It is commonly used in the diagnosis of thyroid tumor and breast tumor. 4.Percutaneous puncture biopsy for pathological diagnosis: With the guidance of B-ultrasound, X-ray TV, CT, etc., the puncture needle is inserted into the lesion and biopsies are taken for pathological diagnosis, which can be clinically used to confirm the diagnosis of lung cancer, liver cancer, gallbladder cancer and pancreatic head cancer.