Clinical symptoms can be artificially divided into pulmonary symptoms directly produced by the primary lesion, symptoms of invasion of adjacent tissues caused by invasion of the primary lesion or metastatic lymph nodes and compression of local adjacent organs, and extra-thoracic organ or systemic symptoms produced by distant metastases and paraneoplastic syndromes, which are often interrelated. (a) Pulmonary symptoms 1. cough. This is the most common initial symptom, and cough almost always occurs in the course of disease development. Initially, it is mostly a dry and mild cough that worsens with time. Sometimes a metallic cough sound can be heard. Pleural invasion is often a painful dry cough. Invasion of the upper mediastinum may be followed by a paroxysmal cough when lying down, and is often convulsive. Sometimes the cough is episodic, or only at night. Sometimes the cough is persistent and persists for a long time. The cough usually worsens with increased activity. 2. Coughing sputum. Coughing sputum is the first symptom in about 15% of patients, and later almost all patients will have different degrees of coughing sputum. The nature and volume of sputum varies. Hematochezia is very common, accounting for about 50% of cases, and hemoptysis with large mouths accounts for about 5% of cases. 3. Chest pain or discomfort. Chest fullness, pain or pressure, aggravated by exertion, position change, coughing or deep breathing, may be wandering. Sometimes it radiates to the neck, back or upper abdomen. Invasion, pressure or irritation of mediastinum, pleura, nerve plexus, intercostal nerve, trachea, bronchus, pulmonary vessels and hilar tissue may cause chest pain. 4. Wheezing. Bronchospasm, tracheal or bronchial partial obstruction resulting in narrowing, may appear asthmatic sound. 5.Shortness of breath. Shortness of breath may occur due to bronchospasm, obstruction, or lung infection, dysplasia, or pleural effusion. The degree of dyspnea varies depending on the pre-disease lung function, the extent of lung lesions and the patient’s tolerance. 6. Fever. Bronchial obstruction and poor drainage of distal secretions can cause different degrees of inflammatory fever, which accounts for about 10% of the initial symptoms and 20%-30% of all lung cancer patients. If lung abscess occurs, it can be manifested as persistent high fever. The possibility of lung cancer should be considered in the case of long-standing pneumonia. (B) Symptoms of adjacent tissue invasion 1. Vocal cord paralysis. The left side may be affected by metastasis to the left upper mediastinal lymph node, and the right side may be affected by metastasis to the supraclavicular lymph node, resulting in hoarseness, swallowing and choking, etc. 2.Septal muscle palsy. If the phrenic nerve is involved, the septal muscle on the affected side is elevated and paradoxical movements occur. 3.Horner syndrome (cervical sympathetic nerve paralysis syndrome). Invasion of the cervical sympathetic nerve pathway is manifested by entropion of the affected eye, ptosis, narrowing of the eyelid, narrowing of the pupil, absence of sweating and hot flushing on the affected side of the face, etc. 4. Difficulty in swallowing. It is caused by compression and invasion of the esophagus. Mediastinal metastatic lymph nodes invade the esophagus and are easily misdiagnosed as esophageal cancer, which is more common in squamous lung cancer. 5.Superior vena cava syndrome (SVCS). It is caused by the obstruction of superior vena cava or saphenous vein. The main symptoms are shortness of breath, cough, edema of the face and neck, chest and upper extremities and headache, which are aggravated in the prone and anterior arch position. Other symptoms are hoarseness, nasal congestion, drowsiness, lethargy, amnesia, dizziness, dysphagia, vertigo, chest pain and rhinorrhea in that order. Clinical signs are edema of the upper extremities and head and neck, jugular venous anger, conjunctival congestion, cyanosis of the lips and mouth, and dark red and cyanotic capillary dilatation of the skin, which is evident in the prone position, with occasional optic disc edema due to nonspecific elevated cranial pressure, possible tongue and laryngeal edema, and possible pleural effusion. The compression above the entrance of the odd vein is manifested only by varicose veins of the head, neck and chest, while compression below the entrance of the odd vein or the vein itself is manifested by dilated veins of the upper arm, lower chest and middle and upper abdominal wall, and occasionally varicose veins of the lower abdominal wall and groin. 6.Pancoast syndrome. Pain in the back of the shoulder and upper limbs caused by carcinoma in the lung tip may be accompanied by abnormal skin sensation (burning-like) and muscle atrophy of different degrees (mainly in the small muscles of the hand, but the upper arm muscles may also be involved), and nerve paralysis may occur in severe cases. The tumor mostly involves the 1st or 2nd rib and vertebral body, and the spinal canal and spinal cord may also be invaded, and spinal cord tumor symptoms are manifested, along with Horner syndrome. Occasionally, it may be combined with superior vena cava syndrome. 7. Cardiac symptoms. The direct involvement or metastasis of pericardium or myocardium may cause cardiac symptoms, such as pericardial effusion, tachycardia, arrhythmia or heart failure. (iii) Extra-thoracic symptoms 1. Extra-pulmonary metastasis. It is not uncommon for lung cancer to have hematogenous metastasis as the first symptom. Metastases to bone (mainly bone pain), liver (mainly hepatomegaly), brain (increased cranial pressure, neurological or psychiatric symptoms), supraclavicular lymph nodes (enlarged and hard), skin (subcutaneous nodules), etc. each have their own manifestations. 2. Paraneoplastic syndrome (1) Systemic symptoms (31%). Anorexia, cachexia, weight loss, fever, wandering thrombophlebitis, upright hypotension, non-bacterial thrombotic endocarditis, polymyositis, systemic lupus erythematosus. (2) Skin symptoms (1%). Secondary hirsutism, acromegaly, pestle and mortar fingers, toes, dermatomyositis, runner’s annular erythema, desquamative erythroderma, hypertrophic osteoarthropathy, superficial thrombophlebitis, hepatic palm, acanthosis nigricans, secondary ichthyosis, secondary palmar toe keratosis, centrifugal annular erythroban, herpes-like dermatitis, extranodal mammary piebald disease, cauliflower skin papilloma, aspergillosis, furunculosis, pruritus, lei – characteristic Sweet’s syndrome, herpes. (3) Endocrine or metabolic symptoms (1%) Cushing’s syndrome, hypercalcemia, hyponatremia, hyperglycemia, hypertension, acromegaly, hyperthyroidism, hypercalcemia, gynecomastia, overflowing breast, carcinoid syndrome, hypoglycemia, hypokalemia, lactic acidosis, hypouricemia, hyperamylasemia. (4) Hematologic symptoms (8%). Anemia, hypercoagulability, thrombocytopenic purpura, amyloidosis, leukocytosis, eosinophilia. (5) Neurological symptoms (1%). Peripheral neuritis, myasthenia gravis syndrome, necrotizing myelopathy, cerebral white matter degeneration, loss of vision, autonomic disorders. (6) Renal symptoms (1%). Glomerulopathy, renal tubulopathy.