Lung cancer, also known as primary bronchogenic carcinoma, is the most common primary malignant tumor of the lung that originates from the bronchial mucosa or glands. Based on histopathological changes, it can be divided into small cell carcinoma and non-small cell carcinoma. Clinical symptoms are often subtle and mainly manifest as cough, expectoration, hemoptysis, and weight loss. Early detection, diagnosis, and treatment lead to a better prognosis, while inadequate early diagnosis can result in a poor prognosis.
Clinical classification
- Classified by anatomical location
(1) Central type lung cancer
Lung cancer that occurs in the bronchial segments and above is more common in squamous cell carcinoma and small cell lung cancer.
(2) Peripheral lung cancer
Adenocarcinoma is more common in lung cancer that occurs below the segmental bronchus.
- Classified by histopathology
(1) Non small cell lung cancer (NSCLC)
It is the most common, accounting for 85% of the total incidence rate of lung cancer.
① Squamous cell carcinoma (SCC): SCC often originates from segmental or subsegmental bronchial mucosa and has a tendency to grow into the lumen. In the early stages, it often causes bronchial stenosis, leading to atelectasis or obstructive pneumonia. Cancer tissue is volatile and necrotic, forming cavities or cancerous lung abscesses. Commonly seen in elderly men. Generally, it grows slower, metastasizes later, has more opportunities for surgical resection, and has a higher 5-year survival rate. However, it is less sensitive to chemotherapy and radiotherapy than small cell lung cancer.
② Adenocarcinoma: It is the most common type of lung cancer. Women are more common, mainly originating from bronchial mucinous glands, which can occur in small bronchi or central airways, and clinically present as peripheral type. Due to the abundance of blood vessels in adenocarcinoma, local infiltration and hematogenous metastasis occur earlier, which can easily involve the pleura and cause pleural effusion.
③ Large cell carcinoma: Large cell carcinoma is an undifferentiated non-small cell carcinoma, which is relatively rare and accounts for less than 10% of lung cancer. It lacks the characteristics of small cell carcinoma, adenocarcinoma, or squamous cell carcinoma in terms of cytology, tissue structure, and immune phenotype. Immunohistochemistry and mucin staining were negative for squamous epithelioid and adenoid differentiation markers. The metastasis of large cell carcinoma is relatively late, and there is a greater chance of surgical resection.
④ Others: Adenosquamous cell carcinoma, sarcomatoid carcinoma, lymphoepitheliomatous carcinoma, NUT carcinoma, salivary gland carcinoma, etc.
(2) Small cell lung cancer (SCLC)
SCLC is a poorly differentiated neuroendocrine tumor that accounts for approximately 15% of lung cancer, including small cell carcinoma and complex small cell carcinoma. Small cell carcinoma cells are small, round or oval in shape, with few cytoplasm and unclear cell edges. The nucleus is granular or deeply stained, with a lack or indistinct nucleolus, and nuclear fission is common. SCLC is characterized by rapid proliferation and early widespread metastasis. Most patients are male and closely related to smoking. It is the most malignant type of lung cancer, with 60% to 88% of patients having brain, liver, bone, or adrenal metastases at the time of initial diagnosis, and only about one-third of patients being confined to the chest. SCLC is mostly of the central type, characterized by pulmonary hilum masses and enlarged mediastinal lymph nodes leading to coughing and difficulty breathing. SCLC surgery has poor resection efficacy and is sensitive to chemotherapy and radiotherapy.
- Classification by clinical disease progression
(1) Staging of non-small cell lung cancer
① Stage I: Early stage of lung cancer, the tumor is located in the lung tissue and has not yet metastasized.
② Stage II: In the middle stage, cancer cells metastasize to lymph nodes near the hilum of the lung.
③ Stage III: In the middle and late stages, cancer cells further metastasize to mediastinal or extrapulmonary lymph nodes.
④ Stage IV: In the late stage, the tumor exhibits pleural metastasis, pleural effusion, or multiple systemic metastases such as brain, liver, bone, etc.
(2) Staging of small cell carcinoma
① Limited period: The tumor is confined to one side of the lung or may have metastasized to nearby lymph nodes, and has not yet metastasized to the other side of the lung or outside the lung. Radical radiotherapy with a radiation field can be accepted.
② Widespread stage: The tumor has already metastasized to both lungs and chest cavity, and may have metastasized to the periphery of the lungs or other areas outside the lungs (such as the liver, brain, bones, etc.).
epidemiology
contagious
Non infectious.
incidence rate
In 2022, there were 1.0606 million new cases of lung cancer, accounting for 22.0% of all malignant tumors.
mortality
In 2022, there were 733300 deaths from lung cancer, accounting for 28.5% of all malignant tumor deaths.
incidence trend
The incidence rate of lung cancer is on the rise.
Easy to reach people
- The population aged 55 to 65 has a high incidence.
- There are more males than females, with a male to female ratio of approximately 2.1:1.
Easy to develop areas
The incidence rate of lung cancer in urban residents is higher than that in rural areas, which may be related to the high level of carcinogens in air pollution and smoke.
cause of disease
executive summary
The etiology of lung cancer is still unclear, and the main pathogenic factors include smoking, occupational exposure, air pollution, ionizing radiation, diet and physical activity, genetics, etc.
underlying cause
- Smoking
Smoking is the most common cause of lung cancer, with approximately 85% of lung cancer patients having a history of smoking, including smokers and those who have quit smoking (defined as quitting smoking for at least 12 months before diagnosis). There is a clear relationship between smoking and lung cancer. The younger the age of starting to smoke, the longer the time of smoking, the larger the amount of smoking, and the higher the incidence rate and mortality of lung cancer. Environmental tobacco smoke, also known as secondhand smoke or passive smoking, is one of the causes of lung cancer. Tobacco has been classified as an A-class carcinogen, and smoking is associated with the risk of all pathological types of lung cancer.
- Occupational exposure
There are many carcinogens present in the working environment of certain professions. Confirmed carcinogens include asbestos, arsenic, dichloromethyl ether, chromium, mustard gas, nickel, polycyclic aromatic hydrocarbons, radon and radon gas produced during the decay of radioactive substances such as uranium and radium, microwave radiation, etc. Due to the long process of lung cancer formation, with a latent period of up to 20 years or longer, many patients develop lung cancer long after stopping exposure to carcinogens.
- Air pollution
(1) Outdoor environmental pollution: Industrial waste gas and automobile exhaust in cities contain carcinogenic substances such as benzo [a] pyrene, arsenic oxide, radioactive substances, nickel, chromium compounds, sulfur dioxide (SO2), nitric oxide (NO), and non combustible aliphatic hydrocarbons.
(2) Indoor environmental pollution: Carcinogens can be produced during fuel combustion and cooking processes. Indoor exposure to coal smoke or its incompletely burned substances is a risk factor for lung cancer, especially for female adenocarcinoma. The oil fume mist released during cooking is also an undeniable carcinogenic factor.
- Ionizing radiation
The lungs are more sensitive to radiation, and high doses of ionizing radiation can increase the risk of lung cancer.
- Diet and physical activity
Studies have shown that low intake of fruits and vegetables during adulthood increases the risk of developing lung cancer. People with low levels of beta carotene in their serum have a higher risk of developing lung cancer. There are also studies showing that moderate to high-intensity physical activity reduces the risk of developing lung tumors by 13% to 30%.
- Genetics
If someone in the family has lung cancer, the individual’s risk of developing lung cancer will increase.
- Other
Viral infections (such as HIV infection), certain chronic lung diseases (such as chronic obstructive pulmonary disease, tuberculosis, sarcoidosis, idiopathic pulmonary fibrosis, and scleroderma), may also be related to the occurrence of lung cancer.
symptom
executive summary
The clinical manifestations are related to the size, type, stage of development, location, presence of metastasis, and complications of the tumor. Lung cancer may have no obvious symptoms, and symptoms only appear when the condition develops to a certain extent. Currently, most lung cancer patients already have symptoms when they seek medical attention, with only 5% to 15% of patients finding lung cancer asymptomatic. The main symptoms of symptomatic patients include bloody sputum, irritating dry cough, wheezing, chest pain, etc.
Typical Symptoms
- Symptoms caused by primary tumor
(1) Cough: Early onset symptoms. It is often a dry cough with little or no phlegm, and can worsen when the tumor causes bronchial stenosis. Mostly persistent, presenting as a high pitched metallic cough or irritating cough. When there is secondary infection, the sputum volume increases and becomes mucopurulent.
(2) Phlegm or hemoptysis: Central type lung cancer is more common, often with blood in sputum or intermittent blood sputum, occasionally with severe hemoptysis.
(3) Asthma: Tumors can cause bronchial stenosis, resulting in partial obstruction and localized wheezing sounds.
(4) Chest tightness and shortness of breath: When a tumor causes bronchial stenosis, or compresses the airway, or spreads to the pleura causing a large amount of pleural effusion and to the pericardium causing pericardial effusion, or when the diaphragm is paralyzed, the superior vena cava is blocked, and the lungs are widely invaded, it can all cause chest tightness and shortness of breath.
(5) Fever: When a tumor compresses or blocks the bronchi, causing pneumonia, atelectasis, or tumor necrosis, it can lead to fever.
(6) Weight loss: a common manifestation of malignant tumors, characterized by loss of appetite due to tumor toxins, infection, and pain in the late stage, which may manifest as weight loss or cachexia.
- Symptoms caused by local expansion of tumors
(1) Chest pain: When a tumor invades the pleura or chest wall, it may present as dull or dull pain, which worsens with breathing and coughing. When invading the ribs and spine, the pain is persistent and significant, and is not related to breathing or coughing. Continuous pain in the shoulder or chest and back often indicates tumor invasion of tissues outside the chest wall.
(2) Dyspnea: Tumors can compress the airway and cause difficulty breathing.
(3) Dysphagia: caused by tumor invasion or compression of the esophagus.
(4) Hoarseness of voice: direct compression of the tumor or compression of the recurrent laryngeal nerve (often on the left side) after metastasis to mediastinal lymph nodes can cause vocal cord paralysis, leading to hoarseness of voice.
(5) Superior vena cava obstruction syndrome: Tumors that directly invade the mediastinum or metastasize to enlarged lymph nodes can compress the superior vena cava, causing obstruction of its reflux and resulting in chest wall varicose veins and upper limb, neck, and facial edema. Severe cases may have dark purple skin, conjunctival congestion, blurred vision, dizziness, and headache.
(6) Horner syndrome: Supranular groove tumor is a type of lung cancer located at the apex of the lung. Cancer invades or compresses the cervical sympathetic nervous system, causing ptosis of the affected eyelid, pupil constriction, and eyeball retraction. There is no or little sweating on the ipsilateral forehead and chest wall, and sensory abnormalities are known as Horner syndrome.
(7) Brachial plexus compression sign: Tumor compression of the brachial plexus can cause radiating and burning pain from the axilla to the inner upper limb on the same side.
Accompanied Symptoms
- Symptoms caused by distant metastasis of tumors
(1) Central nervous system metastasis
There are often signs of increased intracranial pressure such as headache, vomiting, etc. It can also present with neurological symptoms such as dizziness, ataxia, diplopia, personality changes, seizures, or weakness or even hemiplegia on one side of the body. If there is back pain, lower limb weakness, bladder or intestinal dysfunction, there should be a high suspicion of spinal cord compression.
(2) Liver metastasis
May manifest as decreased appetite, abdominal pain, jaundice (such as yellowing of the skin and mucous membranes), etc.
(3) Bone metastasis
Manifested as local pain and tenderness, pathological fractures may also occur. Common sites of bone metastasis include ribs, vertebrae, pelvis, and long bones of limbs.
(4) Adrenal gland metastasis
Symptoms and signs may appear depending on the patient’s hormone secretion, such as Cushing’s syndrome (central obesity, hypertension, etc.).
(5) Lymph node metastasis
The lymph nodes in the supraclavicular fossa are a common site, mostly located behind and below the attachment of the sternocleidomastoid muscle. They can be single or multiple, with a hard fixed mass, gradually increasing in size and quantity, and can fuse without pain or tenderness. Peritoneal lymph node metastasis is also common.
(6) Other
Lung cancer can also metastasize to multiple locations, such as the pancreas, gastrointestinal tract, and kidneys, leading to symptoms such as black stool, abdominal pain, and hematuria.
- Extrapulmonary manifestations of lung cancer
Some lung cancer patients may experience rare symptoms or signs, which are manifested in the external organs of the chest and are not caused by direct tumor action or metastasis. It can appear before or after the discovery of lung cancer, known as paraneoplastic syndrome, also known as extrapulmonary manifestations of lung cancer, with an incidence rate of about 10%.
(1) Endocrine syndrome
It refers to the secretion of bioactive peptides or amines by tumor cells, leading to endocrine abnormalities and corresponding clinical manifestations in patients. Common symptoms include limb pain and weakness, crooked walking, male breast development, abnormal penile erection, nausea, vomiting, abdominal pain, rapid heartbeat, asthma, and skin flushing.
(2) Other
① Hypertrophic osteoarthritis: 30% of patients have clubbed fingers (toes), which are characterized by hyperplasia, thickening, and clubbed swelling at the end of the fingers or toes, mostly NSCLC. Bone inflammation can occur in affected bones, characterized by pain, tenderness, swelling, and other symptoms.
② Multiple peripheral neuropathy: often accompanied by mixed sensory and motor impairments.
③ Abnormal blood system: manifested as skin bleeding points and anemia.
④ Skin manifestations: About 1% of patients may have accompanying skin manifestations, such as echinoderms, dermatomyositis, scleroderma, hyperkeratosis, etc.
complication
Lung cancer may lead to respiratory failure and death due to secondary infections such as pneumonia, pleural effusion, pericardial effusion, etc.