Metastasis is a challenge for most lung cancer patients during the diagnosis and treatment process, and it is also an important cause of eventual death. Some reports suggest that 90% of lung cancer patients die because of metastasis. How does lung cancer actually metastasize? First, direct diffusion: infiltrative growth of tumor cells to its surrounding tissues is a more common metastatic route for all types of lung cancer. The most common way of metastasis for squamous carcinoma is direct diffusion. Second, hematologic metastasis: After cancer cells return to the heart with the pulmonary veins, they can metastasize to any distant parts of the body, most commonly to the brain, bone, liver, adrenal gland and intrapulmonary metastasis. Adenocarcinoma and small cell lung cancer mostly see blood metastasis! Third, lymphatic metastasis: it is the most common metastasis pathway of lung cancer. No matter small cell lung cancer or non-small cell lung cancer, lymphatic metastasis exists in the later stage. Whether small cell lung cancer or non-small cell lung cancer, lymphatic metastasis exists in late stage.