Visiting a hospital and hearing about chemotherapy is always daunting. This is because in most cases, chemotherapy is a treatment for malignant tumors. Many patients with lupus erythematosus visit hospitals, read the drug instructions, and find that they are also using anti-cancer drugs and chemotherapy, and are often shocked: is lupus erythematosus also a kind of cancer? Lupus erythematosus is indeed not cancer, but an autoimmune rheumatic disease. From the perspective of Western medicine, rheumatism is not a disease caused by wind and humidity, but an inflammatory disease caused by various non-infectious and non-neoplastic factors, such as lupus erythematosus, rheumatoid arthritis, dermatomyositis, vasculitis, osteoarthritis, gout and so on, all belong to the category of rheumatism. Most of these rheumatic diseases are caused by “autoimmune” diseases. The so-called “autoimmune”, simply understood, is the immune cells “turn the gun to fight themselves”. The immune system of the human body is like the military system of a country. Under normal circumstances, its main function is to eliminate foreign invaders, such as various bacteria and viruses; organ transplant rejection is also a reaction of the immune system in the rejection of foreign bodies; when there are cell mutations in the body, such as the emergence of cancer cells, the immune system will also work on them to remove the mutated cells. When the immune system is disrupted and “autoimmunity” occurs, it is like an army revolting and “turning its guns around to fight itself”. In this case, the more active the immune cells are, the greater the “killing power” is, and the more serious the disease is. Therefore, it is necessary to use anti-cancer drugs to kill these “rebellious” immune cells. The use of anti-cancer drugs to treat lupus erythematosus is a major advance in the treatment of lupus erythematosus in the past decade or so. Before the 1950s, getting lupus was almost like waiting for death. In the early 1950s, the treatment of lupus erythematosus with hormones began, which enabled many patients to have their acute symptoms controlled, but hormones could not fundamentally relieve the condition of lupus erythematosus and could only reduce the inflammatory damage. In the late 1980s, anti-cancer drugs began to be used in the treatment of lupus erythematosus, resulting in a significant improvement in efficacy. After more than ten years of clinical research and experience, in recent years, the goal of lupus treatment has changed from “prolonging life” in the past to “inducing remission”, allowing lupus to achieve complete remission. If the human body is compared to a city, the autoimmune cells are the terrorists, the body’s own regulatory functions are the security guards, the hormones are the firefighters, and the anti-cancer drugs are the armed forces. A very mild case of lupus erythematosus is like a few lunatics causing trouble in the city, and the security personnel are sufficient to deal with it. If the lunatics set fire to houses, the firefighting force is needed to put out the fire. If many terrorists are setting fires everywhere, relying only on the firefighting force to put out the fires will not solve the root of the problem and the armed police force must be mobilized to suppress the terrorists. In critical erysipelas, it is like a whole city full of terrorists, and relying only on hormones (firefighting forces) will not work at all. Therefore, the more severe lupus erythematosus needs to be treated with anti-cancer drugs, while the very mild patients do not need anti-cancer drugs, but they must be checked regularly and need to adjust their treatment once there are changes in their condition. It is important to know that mild lupus erythematosus can be suddenly aggravated by cold, allergy or for no reason. Under normal circumstances, the number of cells in each part of the body is relatively constant, and the balance of cell metabolism, proliferation and aging death is maintained. The so-called cancer is the mutation of a certain part of the body or a certain kind of cells, and the abnormal active proliferation of the cells, which forms a tumor. The therapeutic mechanism of anti-cancer drugs is to kill those abnormally active cells. Due to the recognition of the pathological mechanism of autoimmunity in lupus erythematosus, the immune cells against themselves in the body of lupus erythematosus patients are very active and proliferate rapidly, thus producing a large number of autoantibodies, which damage various organs of the body. Since anticancer drugs have strong killing power against cells that are actively proliferating, they can kill immune cells against themselves and are effective for lupus erythematosus. Since cells with more active proliferation are more sensitive to anti-cancer drugs, while cells with inactive proliferation are not sensitive to anti-cancer drugs, the majority of cells in normal tissues in the human body will not be harmed by anti-cancer drugs.