Causes of lung cancer:
The exact cause of lung cancer is still unknown. After years of investigation and study, people realize that the following factors are closely related to the etiology of lung cancer.
(1) Smoking According to a large number of survey data in various countries, the cause of lung cancer is closely related to smoking. The increase in the incidence of lung cancer is in step with the increase in cigarette sales. Cigarettes contain many carcinogens such as benzopyrene. The incidence of lung cancer in smokers is 10 times higher than that in non-smokers, and that in heavy smokers is 20 times higher than that in non-smokers. At the end of this century, with the increase of female smokers in western European countries, the incidence of lung cancer among female patients has also increased significantly. Among the clinically diagnosed cases of lung cancer, more than 80% smoked more than 20 cigarettes a day for more than 30 years.
(2) The incidence of lung cancer in developed countries with air pollution is higher in cities than in rural areas, and in factories and mining areas than in residential areas. The main reason is that the combustion of petroleum, coal and internal combustion engine is related to the air pollution caused by harmful substances such as benzopyrene carcinogenic hydrocarbons produced by asphalt pavement dust in developed industrial and transportation areas. Investigation materials show that the incidence of lung cancer increases in areas with high concentration of benzopyrene in the atmosphere.
(3) Occupational factors After years of investigation and study, it has been recognized that long-term exposure to radioactive substances such as uranium, radium and its derivatives, carcinogenic hydrocarbons, arsenic, chromium, nickel, copper, tin, iron, coal tar, asphalt, petroleum, asbestos, mustard gas and other substances can induce lung cancer, mainly squamous cell cancer and undifferentiated small cell cancer.
(4) Chronic lung diseases such as tuberculosis, silicosis and pneumoconiosis can coexist with lung cancer. The incidence of cancer in these cases is higher than that in normal people. In addition, chronic inflammation of lung and bronchus and fibrous scar of lung may cause squamous metaplasia or hyperplasia during the healing process, and on this basis, some cases may develop into cancer.
(5) Internal factors such as family inheritance, decreased immune function, metabolic activity and endocrine dysfunction may also play a certain role in promoting the incidence of lung cancer.
Clinical manifestations of lung cancer patients;
The clinical manifestations of lung cancer are closely related to the location, size, compression, invasion of adjacent organs and metastasis of the tumor. Early lung cancer, especially peripheral lung cancer, often does not produce any symptoms, most of which are found during chest X-ray examination. After the cancer grows up in the larger bronchus, it often produces irritating cough, mostly paroxysmal dry cough or only a small amount of white foam sputum, which is easily mistaken for a cold. When the cancer continues to grow and affects bronchial drainage and secondary lung infection, pus and phlegm can appear and the amount of sputum also increases. Another common symptom is blood sputum, usually a small amount of hemoptysis, with blood spots, bloodshot or intermittent sputum, while a large amount of hemoptysis is rare. Some lung cancer patients may have chest tightness, wheezing, shortness of breath, fever, mild chest pain and other symptoms due to tumor-induced bronchial obstruction.
When advanced lung cancer compresses and invades adjacent organs and tissues or has distant metastasis, it can produce the following symptoms: compressing or invading phrenic nerve, causing ipsilateral phrenic paralysis. Compression or invasion of recurrent laryngeal nerve causes vocal cord paralysis and hoarseness. The superior vena cava is compressed, the veins of face, neck, upper limbs and upper chest are dilated, the tissue is edema, and the venous pressure of upper limbs is increased. Invasion of pleura can cause pleural effusion, which is often bloody. A large amount of fluid accumulation can lead to shortness of breath. In addition, cancer invades the pleura and chest wall, which can cause persistent and severe chest pain. Cancer invades mediastinum and compresses esophagus, which may cause dysphagia. The lungs at the top of the upper lobe can invade and compress organs and tissues located at the upper thoracic orifice. Such as the first rib, subclavian artery and vein, brachial plexus nerve, cervical sympathetic nerve, etc. , severe chest pain, upper limb vein swelling, edema, arm pain and upper limb dyskinesia, ipsilateral upper eye and facial ptosis, pupil contraction, enophthalmos, facial anhidrosis and other cervical sympathetic nerve syndrome groups. After hematogenous metastasis of lung cancer, different symptoms are produced according to the invasion of organs.
In addition, there are a few cases of lung cancer with non-metastatic systemic symptoms due to endocrine substances produced by cancer, such as osteoarthrosis syndrome (clubbing, osteoarthralgia, periosteum hyperplasia, etc. ), Cushing's syndrome, myasthenia gravis, male mammary gland enlargement, multiple muscular neuralgia, etc. These symptoms may disappear after lung cancer resection.
Various examination methods of lung cancer and their significance;
X-ray examination: X-ray examination is one of the most commonly used and important means to diagnose lung cancer. Including fluoroscopy, plain film, tomography, chest computer-aided tomography (CT), magnetic resonance imaging (MRI), bronchography and other methods. The location and size of lung cancer can be known by X-ray examination. The common chest radiograph shows relatively large lesions (slightly larger than the actual volume, which can clearly show density changes, boundary changes, pleural changes, central liquefaction, etc. ), so it is necessary to take plain film first, and then do chest CT if there is confusion. It is superior to ordinary chest film in understanding the lesion site and its relationship with surrounding organs, small pleural implantation or a small amount of effusion, segmental atelectasis, mediastinal lymph node enlargement, and tiny metastasis of lung immortals.
Cytological examination: Most patients with primary lung cancer can find exfoliated cancer cells in sputum and determine the histological types of cancer cells. Therefore, sputum cytology is a simple and effective screening and diagnosis method for lung cancer. The positive rate is only 50% ~ 80%, and there is a false positive of 1% ~ 2%. This method is suitable for the diagnosis of high-risk groups. In order to improve the detection rate, we should pay attention to it from the beginning of expectoration. First of all, we should teach patients to cough up real sputum from the "deep" of the lungs, not just saliva, and stimulate sputum with drugs when necessary. Secondly, when the sputum is fresh, the smear should be fixed before staining and reading.
The positive detection rate of fiberoptic bronchoscopy in bronchoscopy is 60% ~ 80%, and the positive detection rate is far better than that of hard bronchoscopy when the image is enlarged by optical fiber illumination. The pathological changes of endobronchial membrane and lumen can be observed directly through bronchoscope. If you see cancer or cancer infiltration, you can take tissue for pathological examination, or take bronchial secretions for cytological examination to make a clear diagnosis and determine the histological type. Pay attention to the activity of vocal cords, the shape and activity of carina, and the changes of bronchial orifice at all levels (generally up to grade 4 ~ 5) such as tumor, stenosis and ulcer. This kind of inspection is generally complete.
Percutaneous lung puncture is suitable for peripheral lesions, and other methods fail to establish histological diagnosis. At present, fine needle is the first choice, which is safer and has fewer complications. The positive rate of malignant tumor is 74% ~ 96%, and that of benign tumor is 50% ~ 74%. Complications include pneumothorax 20% ~ 35% (about14 needs to be treated), a small amount of hemoptysis 3%, fever 1.3%, air embolism 0.5% and needle implantation 0.02%.
Mediastinoscopy: it is mainly used to determine the extent of mediastinum invasion by central lung cancer. Through the short transverse incision on the upper edge of sternal notch, the cervical girdle muscle and the anterior tracheal fascia were cut longitudinally along the midline. After the innominate artery and aortic arch, the anterior tracheal fascia was separated with fingers by blunt method, and the swollen lymph nodes beside the trachea, tracheobronchial angle and under the carina were observed, and the lymph nodes were punctured, aspirated or cut for pathological examination.
Biopsy of metastatic lesions: when superficial lymph node metastasis or subcutaneous metastatic nodules of clavicle, neck and armpit occur in advanced lung cancer cases, the metastatic lesions can be cut open for pathological section examination or puncture smear examination to make a clear diagnosis.
Bone imaging or emission computed tomography (ECT): Bone imaging can detect bone metastasis earlier because of the increased blood flow, active osteogenesis and vigorous metabolism in bone lesions, and 99mTc-MDP (dimethyl diphosphate) is concentrated in bone lesions, which is found 3 ~ 6 months earlier than ordinary X-ray films. If the lesion has reached the middle stage, the decalcification of bone lesions has reached more than 30% ~ 50% of its content, and both X-ray and bone imaging have positive findings. If the osteogenic reaction is static, metabolism is inactive, bone imaging is negative and X-ray is positive, they can complement each other and improve the diagnostic degree.
Positron computed tomography (PET): Using 2 [18F] fluoro -2- deoxy -d- glucose (FDG) as whole-body positron emission tomography (PET), unexpected chest metastasis can be found. There is no false positive rate in cases of chest metastasis, but there are false positive findings in PET examination of mediastinal granuloma or other inflammatory lymph node lesions. This condition needs to be diagnosed by cytology or biopsy. But there is no doubt that PET can make preoperative periodicity more accurate.
Pathological types of lung cancer:
At present, there is no consensus on the histological classification of lung cancer. According to the morphological characteristics of cancer cells, lung cancer is usually divided into the following main types:
(1) Squamous cell carcinoma is short for squamous cell carcinoma. Squamous cell carcinoma is the most common type of lung cancer, accounting for about 50%. Squamous cell carcinoma mostly originates from larger bronchi, usually central lung cancer. Squamous cell carcinoma has different degrees of differentiation, but generally grows slowly. Squamous cell carcinoma has a long course of disease and its metastasis occurs late. Generally, it first passes through lymphatic metastasis, and then passes through blood metastasis later. The surgical resection rate is high, and the sensitivity to radiotherapy and chemotherapy is not as good as that of undifferentiated cancer.
(2) The undifferentiated small cell cancer cell is similar in shape to the ear of oat, so it is also called oat cell cancer. Undifferentiated small cell carcinoma accounts for about 20% of all types of lung cancer. The onset age is younger, male is more common, and most patients have a history of smoking. Generally originated from the larger bronchi, mostly central lung cancer. Small cell carcinoma has the characteristics of low differentiation, rapid growth, early lymphatic metastasis and invasion of blood vessels, and extensive metastasis to distant organs and tissues in the body, so among all kinds of lung cancer, small cell carcinoma has the worst prognosis. Small cell carcinoma is highly sensitive to radiotherapy and/or anticancer drugs.
(3) Adenocarcinoma Most adenocarcinoma originated from the small mucous epithelial cells of bronchial mucosa, so most adenocarcinoma is located in the peripheral part of the lung, which is spherical and close to the pleura. Female patients are more common and the onset age is younger. It accounts for about 20% of all kinds of lung cancer. Adenocarcinoma is not closely related to smoking, and some cancers occur on the basis of pulmonary fibrous scar lesions. Adenocarcinoma usually has no obvious clinical symptoms in the early stage, which is more common in chest X-ray examination. Cancer grows slowly, but some cases have blood metastasis earlier, and primary lung cancer is often found after symptoms of brain metastasis appear.
(4) Bronchioalveolar carcinoma is a special type of adenocarcinoma with low incidence. It accounts for about 3% of all kinds of lung cancer, which is more common in women. Cancer is often located around the lung field, with good differentiation and slow growth. This type of lung cancer may be closely related to scar lesions caused by lung inflammation. Bronchioalveolar carcinoma is mostly isolated or multiple round nodules, often involving pleura, and a few cases are diffuse infiltration, covering one lung segment, lobe or both lungs, similar to pneumonia or miliary tuberculosis. Cancer cells grow along bronchioloalveolar ducts and alveolar walls and often secrete mucus. Bronchioalveolar carcinoma rarely metastasizes through lymph or blood channels, but it often invades the pleura, produces pleural effusion, or spreads widely through the airway, leading to respiratory failure.
(5) Undifferentiated large cell carcinoma This type of lung cancer is rare, and about half of it originated from the larger bronchus. The tumor is large in size and high in malignancy. Metastasis through lymph or blood occurs earlier, and sometimes the prognosis is poor after brain metastasis is found.
(VI) Bronchial adenoma Bronchial adenoma is a group of primary lung and bronchial tumors originating from mucous glands and glandular duct epithelial cells under bronchial mucosa. The incidence rate is low, accounting for only about 2%. This group of tumors grows slowly, and the boundaries are clear with naked eyes, but they are often eroded.
Adjacent tissues, distant metastasis can occur. Incomplete resection is prone to local recurrence and should be classified as low-grade malignant tumor. Bronchial adenoma often occurs in the larger bronchus, and the tumor is rich in blood vessels, and the onset age is young, which is more common in women. The common clinical symptoms are cough, hemoptysis and pulmonary infection caused by obstructive emphysema, atelectasis or tumor blocking bronchial cavity. There are several types of bronchial adenoma:
1. Bronchial carcinoid is the most common bronchial adenoma. Argyrophilic cells derived from bronchial mucosa containing neurosecretory granules. 90% of the tumor occurred in the large bronchus, which was a central tumor, and 10% occurred in the small bronchus, which was a peripheral tumor.
Carcinoid mainly grows under the bronchial mucosa, and forms a polypoid mass when it protrudes into the bronchial cavity, with smooth surface, rich blood vessels and easy bleeding. In some cases, the tumor grows inside and outside the bronchial wall at the same time, forming masses in the bronchial cavity and lung respectively, which can produce symptoms such as cough, hemoptysis, bronchial obstruction, paraneoplastic syndrome and so on. Bronchial carcinoid generally grows slowly, and the course of disease can be as long as 5 ~ 8 years. However, some cases, especially a few atypical carcinoids, can be transferred to local lymph nodes or distant metastasis through blood. The surgical treatment of bronchial carcinoid tumor has a good effect, and the 5-year survival rate after operation can reach over 80%.
2. Adenoid carcinoma of bronchial cyst, also known as columnar adenoma, is relatively rare in bronchial adenoma. Originated from glandular duct or bronchial mucosa secretory gland. Most of them occur in the lower trachea or proximal main bronchus. The malignant degree is high, and it often erodes the trachea or bronchial wall and its surrounding tissues, which can lead to bronchial cavity obstruction and lymph node or distant metastasis.
3. Mucoepithelioid carcinoma is the rarest of all types of bronchial adenoma. The secretory gland, which originated from the mucous membrane of lung and bronchus, is often polypoid with intact surface mucosa and secretes mucus.
In addition, a few lung cancers may have different histological types in different parts of the same tumor. Squamous cell carcinoma is common in adenocarcinoma, but there may be adenocarcinoma or squamous cell carcinoma coexisting with undifferentiated small cell carcinoma. This kind of lung cancer is called mixed lung cancer. It is rare that two or more primary lung cancer lesions appear in the ipsilateral lung or both lungs at the same time or successively, which is called multiple primary lung cancer. The histological types of these lesions are different from each other, or although the histological types are the same, the origins of the lesions are different and the scope of the lesions exists independently.