Under normal circumstances, the human body’s development process is closely controlled and orderly. After the total number of tissue and organ cells proliferates to a certain number, while a few new cells proliferate and differentiate, some of the cells will die under the regulation of genes, which is called “programmed death” or “apoptosis” in medical science. The total number of cells in a tissue or organ is maintained at a certain number without overgrowth. If there are genetic defects in the genes of human body (e.g. reduced ability to remove carcinogenic substances or insufficient ability to repair gene mutations caused by carcinogenic substances, etc.), and the human body is exposed to the action of carcinogenic factors, which causes the body to undergo gene mutations (or other changes), so that the body loses control of cell proliferation and differentiation, the number of cells will exceed the level that it should be at normal time and “grow like crazy”. The number of cells will exceed the normal level and “grow like crazy”, forming tissue clusters locally, thus forming tumors. Therefore, tumor formation is the result of the organism’s loss of control over the growth and differentiation of tissue cells. So what is a benign tumor and what is a malignant tumor? Tumors are formed when a large number of tumor cells accumulate together. Some tumors are still subject to certain control in the process of growth, the growth of the tumor generally will not detach from the original site, the tumor and the surrounding tissues are clearly demarcated, will not infiltrate into the normal tissues, and show expansive growth, this kind of tumor is called benign tumor. This kind of tumor is called benign tumor. Generally, benign tumors grow slowly and are not easy to recur after surgical resection. Some tumors in the process of growth, infiltrative growth (cells easily invade into the surrounding normal tissues), there will be part of the tumor cells out of the original growth site, to reach some new places to settle down and grow into new tumor foci (this process is called “metastasis”), this kind of infiltrative growth, easy to metastasize the tumor called malignant tumors. Malignant tumors are also commonly known as “cancer”. According to the different tissue sources, malignant tumors (cancer) are divided into two categories: carcinoma (note that it is different from cancer) and sarcoma. Carcinomas are malignant tumors originating from epithelial cells, commonly found in lung cancer, esophageal cancer, and liver cancer. Sarcomas are malignant tumors originating from mesodermal mesenchymal tissues, such as osteosarcoma, rhabdomyosarcoma, and so on. Here is a brief summary of the classification of tumors: Tumor = Benign tumor + Malignant tumor (cancer) Malignant tumor (cancer) = Carcinoma + Sarcoma.