Tuberculosis is a chronic infectious disease caused by Mycobacterium tuberculosis. The human body does not necessarily develop the disease after infection with the tubercle bacilli, but may cause clinical development when resistance is reduced or cell-mediated metaplasia is increased. Patients with TB combined with lung cancer are often found in clinical work, and related studies have found that the risk of finding lung cancer is more than 2.5 times higher than that of the general population with a history of TB for more than 20 years. So what are the causes of TB combined with lung cancer? Immune dysfunction: The TB immune response is a three-stage process of cellular immunity, infection, translation and effect. Sensitized lymphocytes, monocytes, macrophages and NK cells are involved in phagocytosis to kill Mycobacterium tuberculosis, which leads to tuberculosis when their action is diminished. To maintain the stability of the organism’s environment, the immune system can distinguish subsets of T lymphocytes that play an immune surveillance role, recognize mutated cancer cells and senescent cells, and eliminate them through cellular immune mechanisms. Qian Lian et al. showed that lung cancer patients have abnormal cellular immunity, and when cellular immunity is low, cancer cells proliferate and form tumors in the body. It is presumed that tuberculosis combined with lung cancer is the cause of low cellular immune function. Tuberculosis chemotherapy drugs: Wang Deyuan et al. showed that isoniazid has a potential carcinogenic effect on animals. The major metabolite of isoniazid significantly increased the incidence of lung tumors in mice. Rifampin is a potent immunosuppressive agent that blocks the proliferation of human lymphocytes, macrophages and antibodies. When the body is immunocompromised, long-term use of anti-tuberculosis drugs is more likely to inhibit the proliferation of human lymphocytes and macrophages, accelerating and promoting cancer. Tuberculosis chronic lung injury and inflammatory changes: can lead to necrosis, shedding and growth of bronchoalveolar epithelial cells, increasing the possibility of genetic mutations and providing a pathological basis for smoking or other carcinogens. Lung cancer can originate from tuberculosis and the sequelae of pleurisy. Tuberculosis scars can block drainage of the lymphatic system, leading to local accumulation of carcinogens. Calcifications of TB are local mechanical irritants that predispose to carcinogenesis of old scars of TB. The treatment of pulmonary tuberculosis also needs to pay attention to the following aspects: (1) Immune-enhancing agents, such as thymidine, transfer factor and interleukin, can be added to anti-tuberculosis to improve the cellular immune function of the body. (2) In addition to pleurisy, tuberculous meningitis can be treated with hormones for a short period of time. (3) Long-term anti-tuberculosis treatment can induce malignant consequences, and choosing various short-term chemotherapy regimens can reduce the adverse effects of anti-tuberculosis drugs. In conclusion, the occurrence of lung cancer involves many factors and complex processes, and is the result of accumulation of a series of causative factors. The causes of tuberculosis combined with lung cancer are mainly due to the depressed cellular immune function of the body, long-term chronic inflammatory stimulation of tuberculosis lesions, local aggregation of carcinogens in the scar, and on this basis, the prolonged use of anti-TB drugs is also one of the causes of carcinogenesis.