Malignant tumors have now surpassed cardiovascular diseases and become the number one killer of urban residents’ health in China. According to statistics, malignant tumors account for 25% of urban deaths and 21% of rural deaths in China, which means that one out of every four to five people will eventually die from tumors. Tumors themselves are divided into different types depending on the location and tissue, but no matter what type of tumors they are, they can cause harm to people and even bring the threat of death. Tumors are not usually inherent or transmitted from others. It often arises from a genetic mutation in our own body cells. Therefore, if you are at high risk for a certain tumor, it often means that the genes you inherited from your parents may be slightly more susceptible to the tumor than others. Of course, there are many clear cancer-causing factors, such as smoking, radiation, viral hepatitis, etc., but this does not mean that tumors can be prevented, and there are still people who develop tumors with a problem-free lifestyle. The essence of tumor is a group of uncontrolled and uncontrollable cells in the body. Under normal circumstances, our body tells the body cells when to grow and when to divide through some microscopic pathways. However, sometimes some genetic mutations can interfere with this connection and cause the somatic cells to divide and proliferate continuously. This exponential growth of one into two or two into four causes the mutated cells to quickly form cell masses, which is what we call “solid tumors” in our daily life. The unrestricted expansion of tumor is just like the primitive development of city, which requires both large amount of resources and sufficient space. In modern society, we all pursue a rational and sustainable development, but tumors are crazy and endlessly plundering for resources. On the one hand, they seize oxygen and other nutrients from the body through the original blood vessels in the body or new blood vessels of their own, on the other hand, they expand and spread outward to occupy more space through continuous growth, and sometimes even spread directly to other parts of the body through blood vessels, lymphatic vessels and other structures, and continue to take root and germinate and act arbitrarily. In fact, tumor also causes various harm to people’s body through the above two main behaviors. Malignant tumor can cause obstruction in a short period of time due to its rapid growth and outward expansion, and the degree of obstruction is high; for example, esophageal cancer can cause difficulty in swallowing and even develop to complete inability to eat; the progress of colorectal cancer can change patients’ defecation habit and stool shape, which can cause intestinal obstruction and threaten life when the degree is serious. For example, when liver cancer grows rapidly and presses the liver envelope, it can cause severe pain in the right upper abdomen, which is one of the main reasons why more liver cancer patients find out the disease. In addition, if the tumor presses or invades the brain or peripheral nerves, it will cause various corresponding symptoms including pain, numbness, limb weakness, blindness and so on. 2.Invasion and destruction of organ functions Tumor can not only affect the functions of surrounding organs through outward extrusion, but also can infiltrate or penetrate the primary organs, causing more serious consequences. For example, the infiltrative growth of stomach cancer cells can cause malignant ulcer, interfere with the normal peristalsis of stomach, and then affect the digestive function; if the cancer cells further grow and penetrate the stomach wall, it can lead to acute gastric perforation and cause life-threatening consequences; advanced esophageal cancer can also penetrate the esophageal wall and pass through the trachea at the front of esophagus, causing the esophagus and trachea to connect, so that when eating, food can easily enter the trachea, causing inflammation of lung and even suffocation. It may even cause asphyxia. In addition, tumor cells encroaching on the blood vessels in the organs will also cause bleeding of different degrees. Although hemorrhage caused by tumor invasion is not very common, once it happens, the consequences are often fatal. Tumor itself can release some factors that can suppress appetite, lower immune function and damage normal cells of surrounding organs. In addition, due to the rapid growth of malignant tumor, sometimes the new blood vessels and the nutrients plundered cannot meet the needs of tumor itself, then some tumor tissues will often have necrosis, bleeding and infection due to insufficient blood supply. With the death of tumor cells, a large amount of inflammatory factors will be released, which will cause obvious poisoning to the surrounding tissues and enter the blood circulation, causing the dysfunction of immune system of the body. Tumor cells have a strong metabolism, and their endless plundering of nutrition will inevitably cause the lack of nutrition and heat in the body, which will often lead to fatigue, poor appetite, severe emaciation, anemia and even cachexia when the disease is prolonged. Cachexia, also called cachexia, refers to the serious dysfunction of human body caused by chronic diseases such as malignant tumor, and the phenomenon of systemic organ failure, which is one of the main causes of death in the late stage of malignant tumor. In addition, due to the deterioration of systemic nutritional status, the immunity of the patient’s body will be significantly reduced or disrupted, thus weakening or losing the protective function of the body, which is clinically manifested as persistent fever and easy to occur secondary bacterial or viral infection, which is difficult to control. 5.Secretion of hormones affects endocrine function Some tumors of endocrine organs or tumors with neuroendocrine function can secrete hormones and cause endocrine function disorders in human body, thus causing corresponding clinical symptoms. For example, adrenal pheochromocytoma can secrete epinephrine and norepinephrine, which can cause symptoms such as spontaneous increase in blood pressure, severe headache and arrhythmia, while carcinoid tumors in different parts can secrete 5-hydroxytryptamine, histamine and other substances, which can cause typical symptoms such as abdominal pain and diarrhea, skin flushing, tachycardia and asthma. In addition to the physical damage caused by tumor, the psychological impact of tumor on patients is also getting more and more attention. The diagnosis of tumor is a catastrophic news to most of people, and people often have a blank mind, or even the feeling of “the doctor’s lips are still moving, but they can’t hear anything”. After learning the news, patients usually experience a series of strong emotions, such as denial, anger, fear, anxiety, depression, and even despair. At this time, it often takes a while for patients to come to terms with this fact and try to adjust their mindset. If the feeling of anxiety or depression is beyond the scope of self-regulation, then one should take the initiative to seek help, such as confiding in friends and relatives or consulting a psychologist. The above-mentioned are some common hazards of tumors. I hope that through learning, we can further deepen our understanding of tumors’ tricks. In fact, clinically, due to the differences of growth site, tissue type, differentiation degree and disease duration, the manifestations of tumor can be various and varied. We should pay attention to any new symptoms that appear in our body in our daily life and be alert to the possibility of tumor. If we encounter symptoms that are difficult to explain, we should actively seek medical consultation to facilitate early diagnosis and treatment of the disease.