1.What is tumor and what is cancer? Under normal circumstances, the growth and proliferation of each cell are strictly controlled. However, under the effect of carcinogenic factors, a certain cell loses the normal regulation of its growth at the genetic level, resulting in its excessive proliferation, which will form a mass of new organisms, which is a tumor. Tumors are divided into benign and malignant tumors – benign tumors grow only locally, while malignant tumors spread to other parts of the body. Among malignant tumors, they are further divided into carcinoma and sarcoma according to the origin of cells — carcinoma usually originates from superficial cells, such as skin, mucous membrane, etc., while sarcoma originates from middle layer of tissues, such as fat, muscle, bone, etc. So to be exact, cancer is only a part of malignant tumors. However, most people are used to call malignant tumors collectively as cancer. 2.What is precancerous lesion? Precancerous lesion is in the stage of “plausible but not real”, which may or may not be cancer. It has the tendency to become malignant, but not all precancerous lesions will develop into cancer, most of them will be stable for a long time and even recede and recover. At this time, if timely treatment is given, it can be almost 100% cured; if no intervention is made, it may progress to cancer. 3.Where do cancer cells come from? There are two kinds of genes closely related to the occurrence of cancer, namely, proto-oncogene and oncogene. Under normal circumstances, the police (oncogene) is more powerful than the thief (oncogene) and the cell can grow normally. If the thief (oncogene) is “powerful” or the policeman (oncogene) fails to do his job, the normal cells will turn into cancer cells. 4.What factors can cause cancer? Cancer-causing factors can be divided into external and internal factors. Exogenous factors include chemical, physical and biological factors. Common chemical carcinogens include benzene, aflatoxin and nitrosamines; ultraviolet light and ionizing radiation are physical factors; while hepatitis B virus, human papilloma virus and schistosomiasis are biological factors that may cause cancer. Not only the external factors mentioned above are at work, but also the decline of human immunity, long-term depression, depression and serious mental trauma, and other internal factors such as neurological and endocrine disorders are also important reasons for cancer to occur in normal cells. 5.Will everyone get cancer? Although there are many carcinogenic factors in the environment, not all people who are exposed to carcinogens will get cancer because the metabolism of human cells can turn carcinogens into waste and then be discharged from the body. However, they may be transformed into carcinogens that can cause gene mutation by the biological transformation of enzymes. This is the first stage of the cancer formation process, which may take only a few seconds to a few hours. And in the second stage, the final carcinogen acts on the cell. If there is a defect in gene repair, the gene mutates, changing the inherited properties. When the cell divides and multiplies, the next generation of daughter cells receives the wrong information and the morphology changes, becoming cancerous, which in turn slowly develops into a cancerous mass of cells. When it becomes a cancer visible to the naked eye, it appears to be the size of a match head, but already contains 30 million cancer cells. The second stage is quite long, taking about 15-30 years. Because of the long latent period of cancer, cancer patients are mostly elderly.