The etiology and pathogenesis of mediastinal lymph node hyperplasia are extremely complex, and the main etiological factors include chemical exposure, physical rays, biological factors, and genetic factors. It is prevalent in middle-aged and old people, immunocompromised people, patients with mediastinal tumors, and those with a history of the disease in their immediate family members, and patients with lymphomas tend to be at high risk. I. Main etiological factors 1. Chemical factors: deficiency and lack of DNA methylation ability, thus activating oncogenes and inactivating oncogenes, which has obvious organ specificity. There is a wide variety of chemical carcinogens with different results. At present, it is believed that the most important chemical carcinogens for the total cancer risk of human beings are a variety of carcinogenic factors in cigarettes; 2. Physical factors: so far the physical carcinogenic factors that have been affirmed mainly include ionizing radiation, which can be divided into electromagnetic radiation and particle radiation, ultraviolet radiation and some mineral fibers. The important feature of ionizing radiation is that it can release a large amount of energy locally, leading to the breakage of chemical bonds with important biological roles; 3. Biological factors: infectious agents are one of the main causes of human tumors, including viruses, bacteria, parasites, etc.; 4. Hereditary factors: at present, it is believed that the vast majority of the tumors are caused by the above environmental carcinogens, but the same is the same as the exposure to a specific carcinogen, and some people develop tumors, while others do not develop tumors. However, when exposed to the same specific carcinogens, some people develop tumors, while others do not develop tumors. Among them, the genetic characteristics of individuals play an important role in the process of tumor development, therefore, it is an important factor in determining tumor susceptibility, including congenital embryonic dysplasia, which leads to growth, development, differentiation and maturation disorders. Second, predisposing factors 1, viral infection and autoimmune abnormality: infection may directly or indirectly damage pancreatic islet tissues by stimulating autoimmune reaction; 2, long-term staying up late and smoking: long-term staying up late and smoking will lead to disorders of the body’s immune system, which will increase the morbidity rate of patients.