Colorectal cancer can reach the lung through bloodstream metastasis. Clinical symptoms of lung metastasis of colorectal cancer are manifested in the following aspects: a. Chest tightness and breathlessness, which is caused by the formation of pleural fluid and pericardial effusion due to the obstruction of airway by metastases or widespread dissemination, thus causing severe breathing difficulties. Fever, which is caused by metastases with infection or caused by tumor fever. Chest pain, which is mostly caused by metastases causing extensive pleural or local chest wall invasion. Coughing up blood, coughing up blood can be coughing up sputum with blood or small amount of blood or large amount of blood. Cough, which can be dry cough without sputum or with white foamy sputum, can also occur in patients with lung metastasis of intestinal cancer.