I. Principles of TNM staging At the early stage of TNM formation in the mid-20th century, surgery was the main or even the only means of tumor treatment.TNM staging was mainly developed to accommodate surgical treatment.T represents the condition of the primary tumor itself, N represents the invasion of draining lymph nodes, and M represents distant metastasis. Some numbers are appended to the lower right of the three letters of TNM to indicate the extent of deterioration of a specific tumor, such as T0, T1, T2, T3, T4; N0, N1, N2, N3; M0, M1 . T indicates the primary tumor and is divided into four grades (T1, T2, T3, T4) according to the size and local extent of the tumor. The criteria for this grade vary in each site (organ) of the tumor, and two other grades can be added in many departments: Tis (carcinoma in situ) and T0 (no primary tumor seen). N is used to describe the condition of regional lymph nodes and can be classified into four grades (N0, N1, N2, N3) according to the extent of lymph node involvement, the criteria of which vary from site to site. For most tumors, M stands for distant metastasis, M0 for no distant metastasis, and M1 for distant metastasis. Early stage is the absence of lymph node metastasis, intermediate stage is the presence of local lymph node metastasis but still resectable, and advanced stage is synonymous with inoperable resection. These concepts are still in use today, and it can be seen that some of them are inadequate though, and from the present perspective, there should be M2 and M3 again to represent which tissues or organs are invaded respectively, and the degree of invasion should also be indicated. Over the past half century, under the organization of the International Union Against Cancer (UICC) and the American Cancer Society (AJCC), this system has been continuously enriched and improved, and has become the “common language” of clinical oncology. However, from the perspective of clinical research and treatment development in oncology, there are still many shortcomings. In addition, there should be indicators that can reflect the trend (speed) of tumor development and body aspects in order to guide the treatment and predict the possible prognosis more comprehensively. A precise description and histological classification of the extent of cancer invasion at each site can serve the following purposes: 1) to guide clinicians in treatment planning; 2) to predict patient prognosis to a certain extent; 3) to help evaluate the efficacy; 4) to facilitate the exchange of information among treatment centers; and 5) to facilitate the continuous study of human cancers. The scope of tumor invasion can be concisely described by T0, T1, T2, T3, T4; N0, N1, N2, N3; M0, M1. The basic rules applicable to cancers in all parts of the body are: 1. All cases in the TNM classification of each site should be histologically confirmed, and those without histological confirmation should be reported separately. At the same time, necessary tests should be performed to meet the needs of determining T, N and M. There are two classifications for each tumor: (1) Clinical classification (pre-treatment clinical classification): expressed as TNM (or cTNM). This classification is based on evidence obtained from physical examination, imaging, endoscopy, biopsy and various other relevant examinations and surgical exploration before treatment. If detailed classification is needed, subdivision method (T1a, T1b or N2a, N2b, etc.) can be used. (2) Pathological classification (post-surgical histopathological classification): denoted by pTNM. This classification is based on the diagnostic basis obtained before untreated, which is supplemented or modified by other diagnostic bases obtained by surgery and pathological examination. The pathological diagnosis of primary tumor (pT) requires resection of the primary tumor or an examination of the or tissues that provides a maximum estimate of the primary tumor. For pathologic diagnosis of regional lymph nodes (pN), a sufficient number of lymph nodes need to be removed to confirm the most severe grade of regional lymph node free of metastasis (pNO or pN). For pathological diagnosis of distant metastasis (pM), histological examination is required. pT – primary tumor pTx: postoperative histopathological estimation of the primary tumor cannot be made. pTo: No primary tumor was found on postoperative histopathological examination. pTis: carcinoma in situ. pT4: postoperative histologically confirmed extent of primary tumor (in ascending order). pN a regional lymph node pNx: postoperative histopathological estimation of the regional lymph node could not be made. pN0: No regional lymph node metastasis was found on postoperative histopathological examination. PN1,pN2,pN3: the extent of regional lymph node involvement confirmed by histopathology after surgery (in increasing order). (Note: Direct spread of the primary tumor invading lymph nodes is classified as lymph node metastasis. When lymph node size is used as a criterion for pN classification (e.g., breast cancer), the size of the metastatic portion is measured, not the entire lymph node. pM – distant metastasis pMx. No histopathological estimate of distant metastasis can be made; pMo: no distant metastasis on histopathological examination; pMl: histopathological confirmation of distant metastasis. Further designations specifying the site of PMl metastasis are described previously. 2. staging After determining T, N, M and/or PT, PN, PM, the staging can be done accordingly. once the TNM classification and staging are determined, they cannot be changed in the case record. Clinical staging is necessary for selecting treatment plans and evaluating outcomes, while pathological staging provides the most accurate information to estimate prognosis and predict final regression. The TNM system classification is precise and reasonable and documents the anatomical extent of the disease at a glance. For a given tumor, T is classified into four grades, N into three grades, and M into two grades. Thus, there are 24 groups of TNM. Therefore, in order to facilitate analysis and tabular display, it is necessary to group these groups into several appropriate TNM stages. Such staging is adopted in order to make the cancer cases in the same period have a certain degree of consistency in terms of the basis of survival as far as possible, while the survival rates of different periods differ significantly. There are other tumors where TNM staging does not accurately reflect the relationship with prognosis or where the disease is systemic at the time of diagnosis, and therefore a separate staging system is needed to address the treatment issue. Some of the more important ones are small cell lung cancer, lymphoma, leukemia, multiple myeloma, etc.