The trachea, bronchi, fine bronchi and alveoli in the lungs are covered with an inner membrane composed of cells. Because the inner membrane is in direct contact with the atmosphere and because of its rapid growth and metabolism, the majority of lung cancers are malignant from this layer of epidermal cells. The development of malignant tumors in the lung requires many years of growth and evolution. First, precancerous lesions are formed, and then they develop and evolve into cancer cells, at which time the growth of cancer cells accelerates and many chemicals are secreted to stimulate the cancer cells to form blood vessels. Once the blood vessels are created, they will not only inject rich nutrients into the cancer cells to make them grow faster, but will also allow the cancer cells to metastasize to other parts of the body through these vessels. Lung cancer is divided into primary and metastatic. Primary is the malignant transformation of cancer cells from cells in the lung tissue, and metastatic is the migration of malignant tumors from other parts of the body to the lungs through the blood or lymphatic route. Primary bronchopulmonary cancer, referred to as lung cancer, is one of the most common malignant tumors, mostly seen in men over 40 years old, with peak age at 60-79 years old, and currently occupies the fourth place of all tumors in men and the fifth place in women in China. I. Abnormal manifestations 1. Cough is caused by the tumor itself and its secretions stimulating the bronchial mucosa, which is the first symptom of lung cancer, accounting for about 45%. It is characterized by paroxysmal irritating, uncontrollable dry cough with pressure, no sputum or a small amount of white foamy mucous sputum, which may be with blood, and does not heal within 2~3 weeks. If the tumor is located on the mucous membrane of small bronchial tubes, the patient often has no cough or cough is not obvious. 2. Hemoptysis and hematemesis is one of the first symptoms of lung cancer, accounting for 35.9%. It is characterized by intermittent and repeated small amount of bloody sputum, often with more blood than sputum and bright red color, and occasionally large hemoptysis. Because the tumor grows on the bronchial mucosa and the surface is rich in blood vessels, the blood vessels are easily collapsed after severe coughing, so hemoptysis is often the early symptom of central lung cancer. When peripheral lung cancer is small, hemoptysis is less common; when the tumor increases to a certain degree, hemorrhage often occurs when the tumor center is ischemic and necrotic. 3. Chest pain in early stage of lung cancer, there is often irregular chest tightness, pressure or dull pain, which accounts for 30%~40%. When the tumor invades and involves mediastinal pleura, diaphragm and chest wall, severe or persistent chest pain may appear. Peripheral type lung cancer often takes chest pain, back pain, shoulder pain, upper limb pain and intercostal neuralgia as the first symptoms, accounting for about 24%. 4.Shortness of breath is usually more obvious in the late stage of lung cancer, especially when a large amount of pleural fluid appears, and this is the first symptom of 6.6%. 5.Fever is the first symptom in about 21.2% of lung cancer cases. One kind of fever is inflammatory fever caused by bronchial obstruction or lumen compression, and the other is fever caused by infection due to lumen obstruction or narrowing caused by tumor compression of larger bronchus and retention of distal bronchial secretions. 6.Symptoms caused by lung cancer metastasis and tumor compression on adjacent organs, such as tumor compression on superior vena cava causes edema of upper limbs and neck, jugular vein anger, headache and difficulty in breathing. Compression of esophagus can cause difficulty in swallowing. Invasion of the recurrent laryngeal nerve may cause hoarseness. Lymph node metastasis may cause ipsilateral or contralateral supraclavicular mass. When the tumor invades the seventh cervical vertebra and the first thoracic vertebra, it can cause Horner syndrome. Patients present with sunken eyes on the affected side, ptosis of the upper eyelid, narrow pupils, narrow lid fissures, high upper chest temperature on the affected side, and absence of sweating. The symptoms of brachial plexus nerve compression can also be produced, manifested as severe burning-like pain in the upper limb of that side, radiating distally from the medial axilla, and abnormal local skin sensation, etc. 7, extra-pulmonary manifestations of some patients have pestle finger (toe) and bone joint pain, dermatomyositis, muscle weakness-like syndrome, endocrine disorders, carcinoid syndrome and Cushing’s syndrome, etc. These symptoms can even precede the appearance of respiratory symptoms, providing information for early diagnosis. Pestle finger (toe) and osteoarthrosis are more common in our patients, while others are rare. (1) Pestle finger: It is manifested as enlarged hypertrophy of the end of the finger or toe, which becomes pestle-like hypertrophy. It is generally believed to be related to chronic hypoxia, metabolic disorders and toxic damage at the end of the limb. Because lung cancer cells can produce certain special endocrine hormones (heterogenous hormones), antigens and enzymes, these substances operate on bone and joint parts, resulting in swelling and pain of bone and joint, often involving tibia, fibula, ulna, radius and other bones and joints, and the ends of fingers and toes are often enlarged to form pestle-like fingers. (2) Shoulder and back pain: Pulmonary peripheral type lung cancer often develops posteriorly, eroding the pleura and involving the ribs and chest wall tissues, thus causing shoulder and back pain. These patients rarely have respiratory symptoms. (3) Hoarseness: lung cancer metastases compress the laryngeal nerve, which may cause hoarseness due to vocal cord veneer paralysis. Since metastases of lung cancer can appear at an early stage, and the metastases can sometimes grow faster than the primary lesions, the clinical manifestations of metastases can appear before the primary lesions. (4) Neurological symptoms: Brain metastases of lung cancer may show neurological symptoms such as headache, vomiting, sudden coma, aphasia and hemiparesis, which are often misdiagnosed as thrombosis or brain tumor due to the lack of obvious lung symptoms. (5) Male breast hypertrophy: 10%-20% of male lung cancer patients develop breast hypertrophy, some unilateral hypertrophy, but most of them are bilateral hypertrophy, and this symptom appears earlier than pulmonary symptoms such as cough, blood in sputum, chest pain and shortness of breath. This is because some lung cancer cells can secrete chorionic gonadotropin, a hormone that can cause hyperplasia of breast tissue and make the breast enlarged. (6) Carcinoid syndrome: manifested as skin flushing, diarrhea, edema, wheezing, paroxysmal tachycardia, etc., caused by increased 5-hydroxytryptamine and other components. (7) Cushing’s syndrome: manifested as centripetal obesity, purple lines, polycythemia, osteoporosis, etc., caused by elevated adrenocorticotropic hormone. Prevention of lung cancer The epidemiology and etiology of lung cancer prove that the occurrence of lung cancer is closely related to environmental factors. Therefore, controlling and eliminating various carcinogenic factors in the internal and external environment can possibly reduce the incidence and mortality of lung cancer. General rule of prevention: on the one hand, we should reduce or avoid inhaling air and dust containing carcinogenic substances, on the other hand, we should conduct key screening for high-risk groups for early detection and early treatment. These substances not only pollute the air, water and soil, but also contaminate the food, vegetables, fruits, poultry, livestock and fish in these environments, so that many strong carcinogens in the three wastes enter human body through these foods and become potential risk factors for cancer. ① Strictly control harmful substances in the production environment, set up air pollution monitoring institutions, and dynamically observe the air pollution situation in each region. ②Study harmless energy in cities, develop electric vehicles, electrify civilian fuels, and develop solar energy, etc. ③Improve environmental sanitation and do a good job in the treatment of three wastes. 2.Strong control of ionizing radiation strengthen occupational protection, reform the process, do a good job in preventing smoke, dust and pollution, and limit and avoid workers’ exposure to known occupational carcinogens to the maximum extent. 3.Early detection and early treatment ①High-risk groups such as long-term smokers, industrial and mining workers and those with long-term exposure to radioactive substances and those with family history of tumors should be included in the key lung cancer screening population and examined once every 6 months to once a year. ② Actively prevent and treat precancerous lung cancer diseases, such as chronic inflammation of the respiratory tract and chronic respiratory diseases. ③Patients with suspicion should be given high priority, comprehensive examination and early diagnosis, such as cough, hemoptysis, chest pain, hypertrophic arthralgia, pestle-like finger (toe) and muscle weakness-like syndrome over 40 years old with long-standing treatment. ④Popularize the knowledge of lung cancer prevention and treatment, and let the general public understand the early danger signals of lung cancer. 4.Cultivate good living habits ① Limit alcohol consumption, do not eat fried, fried, smoked and baked food, do not eat moldy and spoiled food, pay attention to the frequent consumption of vegetables rich in vitamin A and C such as carotene, and avoid stimulating food and food that produces phlegm and hurts the lungs. ② regular life and living. Pay attention to personal hygiene and strengthen physical exercise. ③ Keep your mood relaxed, avoid worry, sadness and overwork. 5, control smoking, raise awareness of universal participation, the development of relevant regulations ① prohibit underage college, high school and elementary school students smoking, because adolescents are in the growth and development stage, the number of proliferating cells in the body than adults, these proliferating cells are more susceptible to the impact of carcinogens in smoke. ② Prohibit smoking in public places, in public transportation, or in sealed rooms with poor ventilation to reduce the risk to the many passive smokers. ③Severe smokers with a smoking index (number of cigarettes smoked per day x years of smoking) of 400 should be checked regularly to establish three preventions, namely, cancer prevention, consumption prevention and pneumoconiosis prevention. ④Promote vigorously to fully understand the dangers of smoking and encourage quitting. If a universal smoking ban can be achieved one day, about 85% of lung cancers will not arise. As individuals, do not smoke, avoid passive smoking, reduce air pollution in the kitchen improve indoor and outdoor air quality, etc. It has been proven that if you stop smoking, precancerous lesions in the lungs can be transformed into normal cells within 5 years, but the risk of lung cancer is still higher than that of nonsmokers, and if you have precancerous lesions, you are more likely to develop lung cancer from smoking. Passive smokers also have a higher incidence of lung cancer. Lung cancer can be diagnosed early. Early diagnosis is important because lung cancer is difficult to cure when metastases appear. For smokers who are over 40 years old and have the following symptoms, they should be alerted to the possibility of lung cancer and go to the hospital promptly. 1.A prolonged cough that does not resolve for more than 2 weeks. 2.Unexplained chest pain and hoarseness. 3.Loss of weight and decrease in food intake. 4.Hemoptysis or blood in sputum, shortness of breath. 5.Unexplained fever. 6.Recurrent lung infection