Lung Cancer Pathogenesis Interactions between host and environmental factors that can lead to chromosomal deletions and oncogene inactivation are in the preliminary stages of research. Common types of lung cancer include adenocarcinoma, squamous cell carcinoma, large cell undifferentiated carcinoma, and small cell lung cancer. Currently, adenocarcinoma is the most common histopathologic type, accounting for 30-40% of lung cancers; squamous carcinoma was the most common in the past, but has been replaced by adenocarcinoma today. Large-cell undifferentiated carcinoma belongs to the large-cell tissue type but is histologically difficult to classify as squamous or adenocarcinoma. Small cell lung cancer, which is derived from a neuroendocrine cell line, has a faster growth rate, is highly aggressive, and has a poor prognosis. In current lung cancer management strategies, it is not important to distinguish between squamous, adenocarcinomas or large cell carcinomas, but rather between small cell and non-small cell lung cancers. With the continuous growth of lung cancer tissues, and due to the different locations of tumor growth and biological characteristics, various clinical symptoms and outcomes can appear: 1. Space-occupying effect. Tumor tissues cause damage to the organism through the compression of normal tissue structures, such as superior vena cava syndrome or hoarseness caused by compression of the recurrent laryngeal nerve. 2.Invasion of normal tissues, directly leading to tissue damage. For example, the erosion of bones and blood vessels by tumor can cause pain and bleeding; the invasion of pleura and pericardium can cause pleural effusion or pericardial effusion respectively. 3.Obstructing airway, causing obstructive pneumonia, cough and respiratory distress. 4.Produce biological active substances leading to paraneoplastic syndromes, such as syndrome of antidiuretic hormone secretion disorder (SIADH), hypertrophic pulmonary osteoarthropathy, hypercalcemia. Lung cancer can also lead to consumptive changes in the body, weight loss and fatigue, the pathogenesis of which is still unclear. 5.Extrapulmonary metastasis, so that distant organs are involved. Liver, adrenal gland, cranial brain and bones are common extrapulmonary metastatic sites of lung cancer.