Image result for information about lung cancer disease

Lung cancer, also known as lung carcinoma,[7] is a malignant lung tumor characterized by uncontrolled cell growth in tissues of the lung.[10] This growth can spread beyond the lung by the process of metastasis into nearby tissue or other parts of the body.[11] Most cancers that start in the lung, known as primary lung cancers, are carcinomas.[12] The two main types are small-cell lung carcinoma (SCLC) and non-small-cell lung carcinoma (NSCLC).[3] The most common symptoms are coughing (including coughing up blood), weight loss, shortness of breath, and chest pains.[1]

The vast majority (85%) of cases of lung cancer are due to long-term tobacco smoking.[4] About 10–15% of cases occur in people who have never smoked.[13] These cases are often caused by a combination of genetic factors and exposure to radon gas, asbestos, second-hand smoke, or other forms of air pollution.[4][14][5][15] Lung cancer may be seen on chest radiographs and computed tomography (CT) scans.[7] The diagnosis is confirmed by biopsy which is usually performed by bronchoscopy or CT-guidance.[6][16]

Avoidance of risk factors, including smoking and air pollution, is the primary method of prevention.[17] Treatment and long-term outcomes depend on the type of cancer, the stage (degree of spread), and the person's overall health.[7] Most cases are not curable.[3] Common treatments include surgery, chemotherapy, and radiotherapy.[7] NSCLC is sometimes treated with surgery, whereas SCLC usually responds better to chemotherapy and radiotherapy.[18]

Worldwide in 2012, lung cancer occurred in 1.8 million people and resulted in 1.6 million deaths.[12] This makes it the most common cause of cancer-related death in men and second most common in women after breast cancer.[19] The most common age at diagnosis is 70 years.[2] Overall, 17.4% of people in the United States diagnosed with lung cancer survive five years after the diagnosis,[2] while outcomes on average are worse in the developing world.[20]


Respiratory symptoms: coughing, coughing up blood, wheezing, or shortness of breath
Systemic symptoms: weight loss, weakness, fever, or clubbing of the fingernails
Symptoms due to the cancer mass pressing on adjacent structures: chest pain, bone pain, superior vena cava obstruction, or difficulty swallowing
If the cancer grows in the airways, it may obstruct airflow, causing breathing difficulties. The obstruction can lead to accumulation of secretions behind the blockage, and predispose to pneumonia.[1]

Depending on the type of tumor, paraneoplastic phenomena—symptoms not due to the local presence of cancer—may initially attract attention to the disease.[21] In lung cancer, these phenomena may include hypercalcemia, syndrome of inappropriate antidiuretic hormone (SIADH, abnormally concentrated urine and diluted blood), ectopic ACTH production, or Lambert–Eaton myasthenic syndrome (muscle weakness due to autoantibodies). Tumors in the top of the lung, known as Pancoast tumors, may invade the local part of the sympathetic nervous system, leading to Horner's syndrome (dropping of the eyelid and a small pupil on that side), as well as damage to the brachial plexus.[1]

Many of the symptoms of lung cancer (poor appetite, weight loss, fever, fatigue) are not specific.[6] In many people, the cancer has already spread beyond the original site by the time they have symptoms and seek medical attention.[22] Symptoms that suggest the presence of metastatic disease include weight loss, bone pain and neurological symptoms (headaches, fainting, convulsions, or limb weakness).[1] Common sites of spread include the brain, bone, adrenal glands, opposite lung, liver, pericardium, and kidneys.[22] About 10% of people with lung cancer do not have symptoms at diagnosis; these cancers are incidentally found on routine chest radiography.[16]

Causes

Relationship between cigarette consumption per person (blue) and male lung cancer rates (green) in the US over the century.

Risk of death from lung cancer is strongly correlated with smoking
Cancer develops following genetic damage to DNA and epigenetic changes. These changes affect the normal functions of the cell, including cell proliferation, programmed cell death (apoptosis) and DNA repair. As more damage accumulates, the risk of cancer increases.[23]

Smoking
Tobacco smoking is by far the main contributor to lung cancer.[4] Cigarette smoke contains at least 73 known carcinogens,[24] including benzo[a]pyrene,[25] NNK, 1,3-butadiene and a radioactive isotope of polonium, polonium-210.[24] Across the developed world, 90% of lung cancer deaths in men during the year 2000 were attributed to smoking (70% for women).[26] Smoking accounts for about 85% of lung cancer cases.[7]

Passive smoking—the inhalation of smoke from another's smoking—is a cause of lung cancer in nonsmokers. A passive smoker can be defined as someone living or working with a smoker. Studies from the US,[27][28][29] Europe[30] and the UK[31] have consistently shown a significantly increased risk among those exposed to passive smoke.[32] Those who live with someone who smokes have a 20–30% increase in risk while those who work in an environment with secondhand smoke have a 16–19% increase in risk.[33] Investigations of sidestream smoke suggest it is more dangerous than direct smoke.[34] Passive smoking causes about 3,400 deaths from lung cancer each year in the USA.[29]

Marijuana smoke contains many of the same carcinogens as those in tobacco smoke.[35] However, the effect of smoking cannabis on lung cancer risk is not clear.[36][37] A 2013 review did not find an increased risk from light to moderate use.[38] A 2014 review found that smoking cannabis doubled the risk of lung cancer.[39]

Radon gas
Radon is a colorless and odorless gas generated by the breakdown of radioactive radium, which in turn is the decay product of uranium, found in the Earth's crust. The radiation decay products ionize genetic material, causing mutations that sometimes turn cancerous. Radon is the second-most common cause of lung cancer in the USA,[40] causing about 21,000 deaths each year.[41] The risk increases 8–16% for every 100 Bq/m³ increase in the radon concentration.[42] Radon gas levels vary by locality and the composition of the underlying soil and rocks. About one in 15 homes in the US has radon levels above the recommended guideline of 4 picocuries per liter (pCi/l) (148 Bq/m³).[43]

Asbestos
Asbestos can cause a variety of lung diseases, including lung cancer. Tobacco smoking and asbestos have a synergistic effect on the formation of lung cancer.[5] In smokers who work with asbestos, the risk of lung cancer is increased 45-fold compared to the general population.[44] Asbestos can also cause cancer of the pleura, called mesothelioma (which is different from lung cancer).[45]

Air pollution
Outdoor air pollutants, especially chemicals released from the burning of fossil fuels, increase the risk of lung cancer.[4] Fine particulates (PM2.5) and sulfate aerosols, which may be released in traffic exhaust fumes, are associated with slightly increased risk.[4][46] For nitrogen dioxide, an incremental increase of 10 parts per billion increases the risk of lung cancer by 14%.[47] Outdoor air pollution is estimated to account for 1–2% of lung cancers.[4]

Tentative evidence supports an increased risk of lung cancer from indoor air pollution related to the burning of wood, charcoal, dung or crop residue for cooking and heating.[48] Women who are exposed to indoor coal smoke have about twice the risk and a number of the by-products of burning biomass are known or suspected carcinogens.[49] This risk affects about 2.4 billion people globally,[48] and is believed to account for 1.5% of lung cancer deaths.[49]

Genetics
About 8% of lung cancer is due to inherited factors.[50] In relatives of people with lung cancer, the risk is doubled. This is likely due to a combination of genes.[51] Polymorphisms on chromosomes 5, 6 and 15 are known to affect the risk of lung cancer.[52]

Other causes
Numerous other substances, occupations, and environmental exposures have been linked to lung cancer. The International Agency for Research on Cancer (IARC) states there is "sufficient evidence" to show the following are carcinogenic in the lungs:[53]

Some metals (aluminum production, cadmium and cadmium compounds, chromium(VI) compounds, beryllium and beryllium compounds, iron and steel founding, nickel compounds, arsenic and inorganic arsenic compounds, underground hematite mining)
Some products of combustion (incomplete combustion, coal (indoor emissions from household coal burning), coal gasification, coal-tar pitch, coke production, soot, diesel engine exhaust)
Ionizing radiation (X-radiation, gamma radiation, plutonium)
Some toxic gases (methyl ether (technical grade), Bis-(chloromethyl) ether, sulfur mustard, MOPP (vincristine-prednisone-nitrogen mustard-procarbazine mixture), fumes from painting)
Rubber production and crystalline silica dust
Pathogenesis
See also: Carcinogenesis

False-color scanning electron micrograph of a lung cancer cell dividing
Similar to many other cancers, lung cancer is initiated by activation of oncogenes or inactivation of tumor suppressor genes.[54] Carcinogens cause mutations in these genes which induce the development of cancer.[55]

Mutations in the K-ras proto-oncogene are responsible for 10–30% of lung adenocarcinomas.[56][57] About 4% of non-small-cell lung carcinomas involve an EML4-ALK tyrosine kinase fusion gene.[58]

Epigenetic changes—such as alteration of DNA methylation, histone tail modification, or microRNA regulation—may lead to inactivation of tumor suppressor genes.[59]

The epidermal growth factor receptor (EGFR) regulates cell proliferation, apoptosis, angiogenesis, and tumor invasion.[56] Mutations and amplification of EGFR are common in non-small-cell lung carcinoma and provide the basis for treatment with EGFR-inhibitors. Her2/neu is affected less frequently.[56] Other genes that are often mutated or amplified are c-MET, NKX2-1, LKB1, PIK3CA, and BRAF.[56]

The cell lines of origin are not fully understood.[1] The mechanism may involve abnormal activation of stem cells. In the proximal airways, stem cells that express keratin 5 are more likely to be affected, typically leading to squamous-cell lung carcinoma. In the middle airways, implicated stem cells include club cells and neuroepithelial cells that express club cell secretory protein. Small-cell lung carcinoma may be derived from these cell lines[60] or neuroendocrine cells,[1] and may express CD44.[60]

Metastasis of lung cancer requires transition from epithelial to mesenchymal cell type. This may occur through activation of signaling pathways such as Akt/GSK3Beta, MEK-ERK, Fas, and Par6.[61]

Diagnosis

CT scan showing a cancerous tumor in the left lung
Performing a chest radiograph is one of the first investigative steps if a person reports symptoms that may suggest lung cancer. This may reveal an obvious mass, widening of the mediastinum (suggestive of spread to lymph nodes there), atelectasis (collapse), consolidation (pneumonia) or pleural effusion.[7] CT imaging is typically used to provide more information about the type and extent of disease. Bronchoscopy or CT-guided biopsy is often used to sample the tumor for histopathology.[16]

Lung cancer often appears as a solitary pulmonary nodule on a chest radiograph. However, the differential diagnosis is wide. Many other diseases can also give this appearance, including metastatic cancer, hamartomas, and infectious granulomas such as tuberculosis, histoplasmosis and coccidioidomycosis.[62] Lung cancer can also be an incidental finding, as a solitary pulmonary nodule on a chest radiograph or CT scan done for an unrelated reason.[63] The definitive diagnosis of lung cancer is based on histological examination of the suspicious tissue[1] in the context of the clinical and radiological features.[6]

Clinical practice guidelines recommend frequencies for pulmonary nodule surveillance.[64] CT imaging should not be used for longer or more frequently than indicated as extended surveillance exposes people to increased radiation.[64]

Classification

Pie chart showing incidences of non-small cell lung cancers as compared to small cell carcinoma shown at right, with fractions of smokers versus non-smokers shown for each type.[65]
Age-adjusted incidence of lung cancer by histological type[4]

Lung cancers are classified according to histological type.[6] This classification is important for determining management and predicting outcomes of the disease. Lung cancers are carcinomas—malignancies that arise from epithelial cells. Lung carcinomas are categorized by the size and appearance of the malignant cells seen by a histopathologist under a microscope. For therapeutic purposes, two broad classes are distinguished: non-small-cell lung carcinoma and small-cell lung carcinoma.[66]

Nearly 40% of lung cancers are adenocarcinoma, which usually originates in peripheral lung tissue.[6] Although most cases of adenocarcinoma are associated with smoking, adenocarcinoma is also the most common form of lung cancer among people who have smoked fewer than 100 cigarettes in their lifetimes ("never-smokers")[1][67] and ex-smokers with a modest smoking history.[1] A subtype of adenocarcinoma, the bronchioloalveolar carcinoma, is more common in female never-smokers, and may have a better long-term survival.[68]

Squamous-cell carcinoma accounts for about 30% of lung cancers. They typically occur close to large airways. A hollow cavity and associated cell death are commonly found at the center of the tumor.[6] About 9% of lung cancers are large-cell carcinoma. These are so named because the cancer cells are large, with excess cytoplasm, large nuclei and conspicuous nucleoli.[6]

Small-cell lung carcinoma

Small-cell lung carcinoma (microscopic view of a core needle biopsy)
In small-cell lung carcinoma (SCLC), the cells contain dense neurosecretory granules (vesicles containing neuroendocrine hormones), which give this tumor an endocrine/paraneoplastic syndrome association.[69] Most cases arise in the larger airways (primary and secondary bronchi).[16] Sixty to seventy percent have extensive disease (which cannot be targeted within a single radiation therapy field) at presentation.[1]

Others
Four main histological subtypes are recognised, although some cancers may contain a combination of different subtypes,[66] such as adenosquamous carcinoma.[6] Rare subtypes include carcinoid tumors, bronchial gland carcinomas and sarcomatoid carcinomas.[6]

Metastasis
The lung is a common place for the spread of tumors from other parts of the body. Secondary cancers are classified by the site of origin; e.g., breast cancer that has spread to the lung is called metastatic breast cancer. Metastases often have a characteristic round appearance on chest radiograph.[70]

Primary lung cancers themselves most commonly metastasize to the brain, bones, liver and adrenal glands.[6] Immunostaining of a biopsy is often helpful to determine the original source.[71] The presence of Napsin-A, TTF-1, CK7 and CK20 are helpful in confirming the subtype of lung carcinoma. SCLC derived from neuroendocrine cells may express CD56, neural cell adhesion molecule, synaptophysin or chromogranin.[1]

Staging
Lung cancer staging is an assessment of the degree of spread of the cancer from its original source.[72] It is one of the factors affecting the prognosis and potential treatment of lung cancer.[1][72]

The evaluation of non-small-cell lung carcinoma (NSCLC) staging uses the TNM classification. This is based on the size of the primary tumor, lymph node involvement, and distant metastasis.[1]

Lung Cancer

Image result for information about lung cancer disease

Lung cancer, also known as lung carcinoma,[7] is a malignant lung tumor characterized by uncontrolled cell growth in tissues of the lung.[10] This growth can spread beyond the lung by the process of metastasis into nearby tissue or other parts of the body.[11] Most cancers that start in the lung, known as primary lung cancers, are carcinomas.[12] The two main types are small-cell lung carcinoma (SCLC) and non-small-cell lung carcinoma (NSCLC).[3] The most common symptoms are coughing (including coughing up blood), weight loss, shortness of breath, and chest pains.[1]

The vast majority (85%) of cases of lung cancer are due to long-term tobacco smoking.[4] About 10–15% of cases occur in people who have never smoked.[13] These cases are often caused by a combination of genetic factors and exposure to radon gas, asbestos, second-hand smoke, or other forms of air pollution.[4][14][5][15] Lung cancer may be seen on chest radiographs and computed tomography (CT) scans.[7] The diagnosis is confirmed by biopsy which is usually performed by bronchoscopy or CT-guidance.[6][16]

Avoidance of risk factors, including smoking and air pollution, is the primary method of prevention.[17] Treatment and long-term outcomes depend on the type of cancer, the stage (degree of spread), and the person's overall health.[7] Most cases are not curable.[3] Common treatments include surgery, chemotherapy, and radiotherapy.[7] NSCLC is sometimes treated with surgery, whereas SCLC usually responds better to chemotherapy and radiotherapy.[18]

Worldwide in 2012, lung cancer occurred in 1.8 million people and resulted in 1.6 million deaths.[12] This makes it the most common cause of cancer-related death in men and second most common in women after breast cancer.[19] The most common age at diagnosis is 70 years.[2] Overall, 17.4% of people in the United States diagnosed with lung cancer survive five years after the diagnosis,[2] while outcomes on average are worse in the developing world.[20]


Respiratory symptoms: coughing, coughing up blood, wheezing, or shortness of breath
Systemic symptoms: weight loss, weakness, fever, or clubbing of the fingernails
Symptoms due to the cancer mass pressing on adjacent structures: chest pain, bone pain, superior vena cava obstruction, or difficulty swallowing
If the cancer grows in the airways, it may obstruct airflow, causing breathing difficulties. The obstruction can lead to accumulation of secretions behind the blockage, and predispose to pneumonia.[1]

Depending on the type of tumor, paraneoplastic phenomena—symptoms not due to the local presence of cancer—may initially attract attention to the disease.[21] In lung cancer, these phenomena may include hypercalcemia, syndrome of inappropriate antidiuretic hormone (SIADH, abnormally concentrated urine and diluted blood), ectopic ACTH production, or Lambert–Eaton myasthenic syndrome (muscle weakness due to autoantibodies). Tumors in the top of the lung, known as Pancoast tumors, may invade the local part of the sympathetic nervous system, leading to Horner's syndrome (dropping of the eyelid and a small pupil on that side), as well as damage to the brachial plexus.[1]

Many of the symptoms of lung cancer (poor appetite, weight loss, fever, fatigue) are not specific.[6] In many people, the cancer has already spread beyond the original site by the time they have symptoms and seek medical attention.[22] Symptoms that suggest the presence of metastatic disease include weight loss, bone pain and neurological symptoms (headaches, fainting, convulsions, or limb weakness).[1] Common sites of spread include the brain, bone, adrenal glands, opposite lung, liver, pericardium, and kidneys.[22] About 10% of people with lung cancer do not have symptoms at diagnosis; these cancers are incidentally found on routine chest radiography.[16]

Causes

Relationship between cigarette consumption per person (blue) and male lung cancer rates (green) in the US over the century.

Risk of death from lung cancer is strongly correlated with smoking
Cancer develops following genetic damage to DNA and epigenetic changes. These changes affect the normal functions of the cell, including cell proliferation, programmed cell death (apoptosis) and DNA repair. As more damage accumulates, the risk of cancer increases.[23]

Smoking
Tobacco smoking is by far the main contributor to lung cancer.[4] Cigarette smoke contains at least 73 known carcinogens,[24] including benzo[a]pyrene,[25] NNK, 1,3-butadiene and a radioactive isotope of polonium, polonium-210.[24] Across the developed world, 90% of lung cancer deaths in men during the year 2000 were attributed to smoking (70% for women).[26] Smoking accounts for about 85% of lung cancer cases.[7]

Passive smoking—the inhalation of smoke from another's smoking—is a cause of lung cancer in nonsmokers. A passive smoker can be defined as someone living or working with a smoker. Studies from the US,[27][28][29] Europe[30] and the UK[31] have consistently shown a significantly increased risk among those exposed to passive smoke.[32] Those who live with someone who smokes have a 20–30% increase in risk while those who work in an environment with secondhand smoke have a 16–19% increase in risk.[33] Investigations of sidestream smoke suggest it is more dangerous than direct smoke.[34] Passive smoking causes about 3,400 deaths from lung cancer each year in the USA.[29]

Marijuana smoke contains many of the same carcinogens as those in tobacco smoke.[35] However, the effect of smoking cannabis on lung cancer risk is not clear.[36][37] A 2013 review did not find an increased risk from light to moderate use.[38] A 2014 review found that smoking cannabis doubled the risk of lung cancer.[39]

Radon gas
Radon is a colorless and odorless gas generated by the breakdown of radioactive radium, which in turn is the decay product of uranium, found in the Earth's crust. The radiation decay products ionize genetic material, causing mutations that sometimes turn cancerous. Radon is the second-most common cause of lung cancer in the USA,[40] causing about 21,000 deaths each year.[41] The risk increases 8–16% for every 100 Bq/m³ increase in the radon concentration.[42] Radon gas levels vary by locality and the composition of the underlying soil and rocks. About one in 15 homes in the US has radon levels above the recommended guideline of 4 picocuries per liter (pCi/l) (148 Bq/m³).[43]

Asbestos
Asbestos can cause a variety of lung diseases, including lung cancer. Tobacco smoking and asbestos have a synergistic effect on the formation of lung cancer.[5] In smokers who work with asbestos, the risk of lung cancer is increased 45-fold compared to the general population.[44] Asbestos can also cause cancer of the pleura, called mesothelioma (which is different from lung cancer).[45]

Air pollution
Outdoor air pollutants, especially chemicals released from the burning of fossil fuels, increase the risk of lung cancer.[4] Fine particulates (PM2.5) and sulfate aerosols, which may be released in traffic exhaust fumes, are associated with slightly increased risk.[4][46] For nitrogen dioxide, an incremental increase of 10 parts per billion increases the risk of lung cancer by 14%.[47] Outdoor air pollution is estimated to account for 1–2% of lung cancers.[4]

Tentative evidence supports an increased risk of lung cancer from indoor air pollution related to the burning of wood, charcoal, dung or crop residue for cooking and heating.[48] Women who are exposed to indoor coal smoke have about twice the risk and a number of the by-products of burning biomass are known or suspected carcinogens.[49] This risk affects about 2.4 billion people globally,[48] and is believed to account for 1.5% of lung cancer deaths.[49]

Genetics
About 8% of lung cancer is due to inherited factors.[50] In relatives of people with lung cancer, the risk is doubled. This is likely due to a combination of genes.[51] Polymorphisms on chromosomes 5, 6 and 15 are known to affect the risk of lung cancer.[52]

Other causes
Numerous other substances, occupations, and environmental exposures have been linked to lung cancer. The International Agency for Research on Cancer (IARC) states there is "sufficient evidence" to show the following are carcinogenic in the lungs:[53]

Some metals (aluminum production, cadmium and cadmium compounds, chromium(VI) compounds, beryllium and beryllium compounds, iron and steel founding, nickel compounds, arsenic and inorganic arsenic compounds, underground hematite mining)
Some products of combustion (incomplete combustion, coal (indoor emissions from household coal burning), coal gasification, coal-tar pitch, coke production, soot, diesel engine exhaust)
Ionizing radiation (X-radiation, gamma radiation, plutonium)
Some toxic gases (methyl ether (technical grade), Bis-(chloromethyl) ether, sulfur mustard, MOPP (vincristine-prednisone-nitrogen mustard-procarbazine mixture), fumes from painting)
Rubber production and crystalline silica dust
Pathogenesis
See also: Carcinogenesis

False-color scanning electron micrograph of a lung cancer cell dividing
Similar to many other cancers, lung cancer is initiated by activation of oncogenes or inactivation of tumor suppressor genes.[54] Carcinogens cause mutations in these genes which induce the development of cancer.[55]

Mutations in the K-ras proto-oncogene are responsible for 10–30% of lung adenocarcinomas.[56][57] About 4% of non-small-cell lung carcinomas involve an EML4-ALK tyrosine kinase fusion gene.[58]

Epigenetic changes—such as alteration of DNA methylation, histone tail modification, or microRNA regulation—may lead to inactivation of tumor suppressor genes.[59]

The epidermal growth factor receptor (EGFR) regulates cell proliferation, apoptosis, angiogenesis, and tumor invasion.[56] Mutations and amplification of EGFR are common in non-small-cell lung carcinoma and provide the basis for treatment with EGFR-inhibitors. Her2/neu is affected less frequently.[56] Other genes that are often mutated or amplified are c-MET, NKX2-1, LKB1, PIK3CA, and BRAF.[56]

The cell lines of origin are not fully understood.[1] The mechanism may involve abnormal activation of stem cells. In the proximal airways, stem cells that express keratin 5 are more likely to be affected, typically leading to squamous-cell lung carcinoma. In the middle airways, implicated stem cells include club cells and neuroepithelial cells that express club cell secretory protein. Small-cell lung carcinoma may be derived from these cell lines[60] or neuroendocrine cells,[1] and may express CD44.[60]

Metastasis of lung cancer requires transition from epithelial to mesenchymal cell type. This may occur through activation of signaling pathways such as Akt/GSK3Beta, MEK-ERK, Fas, and Par6.[61]

Diagnosis

CT scan showing a cancerous tumor in the left lung
Performing a chest radiograph is one of the first investigative steps if a person reports symptoms that may suggest lung cancer. This may reveal an obvious mass, widening of the mediastinum (suggestive of spread to lymph nodes there), atelectasis (collapse), consolidation (pneumonia) or pleural effusion.[7] CT imaging is typically used to provide more information about the type and extent of disease. Bronchoscopy or CT-guided biopsy is often used to sample the tumor for histopathology.[16]

Lung cancer often appears as a solitary pulmonary nodule on a chest radiograph. However, the differential diagnosis is wide. Many other diseases can also give this appearance, including metastatic cancer, hamartomas, and infectious granulomas such as tuberculosis, histoplasmosis and coccidioidomycosis.[62] Lung cancer can also be an incidental finding, as a solitary pulmonary nodule on a chest radiograph or CT scan done for an unrelated reason.[63] The definitive diagnosis of lung cancer is based on histological examination of the suspicious tissue[1] in the context of the clinical and radiological features.[6]

Clinical practice guidelines recommend frequencies for pulmonary nodule surveillance.[64] CT imaging should not be used for longer or more frequently than indicated as extended surveillance exposes people to increased radiation.[64]

Classification

Pie chart showing incidences of non-small cell lung cancers as compared to small cell carcinoma shown at right, with fractions of smokers versus non-smokers shown for each type.[65]
Age-adjusted incidence of lung cancer by histological type[4]

Lung cancers are classified according to histological type.[6] This classification is important for determining management and predicting outcomes of the disease. Lung cancers are carcinomas—malignancies that arise from epithelial cells. Lung carcinomas are categorized by the size and appearance of the malignant cells seen by a histopathologist under a microscope. For therapeutic purposes, two broad classes are distinguished: non-small-cell lung carcinoma and small-cell lung carcinoma.[66]

Nearly 40% of lung cancers are adenocarcinoma, which usually originates in peripheral lung tissue.[6] Although most cases of adenocarcinoma are associated with smoking, adenocarcinoma is also the most common form of lung cancer among people who have smoked fewer than 100 cigarettes in their lifetimes ("never-smokers")[1][67] and ex-smokers with a modest smoking history.[1] A subtype of adenocarcinoma, the bronchioloalveolar carcinoma, is more common in female never-smokers, and may have a better long-term survival.[68]

Squamous-cell carcinoma accounts for about 30% of lung cancers. They typically occur close to large airways. A hollow cavity and associated cell death are commonly found at the center of the tumor.[6] About 9% of lung cancers are large-cell carcinoma. These are so named because the cancer cells are large, with excess cytoplasm, large nuclei and conspicuous nucleoli.[6]

Small-cell lung carcinoma

Small-cell lung carcinoma (microscopic view of a core needle biopsy)
In small-cell lung carcinoma (SCLC), the cells contain dense neurosecretory granules (vesicles containing neuroendocrine hormones), which give this tumor an endocrine/paraneoplastic syndrome association.[69] Most cases arise in the larger airways (primary and secondary bronchi).[16] Sixty to seventy percent have extensive disease (which cannot be targeted within a single radiation therapy field) at presentation.[1]

Others
Four main histological subtypes are recognised, although some cancers may contain a combination of different subtypes,[66] such as adenosquamous carcinoma.[6] Rare subtypes include carcinoid tumors, bronchial gland carcinomas and sarcomatoid carcinomas.[6]

Metastasis
The lung is a common place for the spread of tumors from other parts of the body. Secondary cancers are classified by the site of origin; e.g., breast cancer that has spread to the lung is called metastatic breast cancer. Metastases often have a characteristic round appearance on chest radiograph.[70]

Primary lung cancers themselves most commonly metastasize to the brain, bones, liver and adrenal glands.[6] Immunostaining of a biopsy is often helpful to determine the original source.[71] The presence of Napsin-A, TTF-1, CK7 and CK20 are helpful in confirming the subtype of lung carcinoma. SCLC derived from neuroendocrine cells may express CD56, neural cell adhesion molecule, synaptophysin or chromogranin.[1]

Staging
Lung cancer staging is an assessment of the degree of spread of the cancer from its original source.[72] It is one of the factors affecting the prognosis and potential treatment of lung cancer.[1][72]

The evaluation of non-small-cell lung carcinoma (NSCLC) staging uses the TNM classification. This is based on the size of the primary tumor, lymph node involvement, and distant metastasis.[1]

1 comment:

Florence said...

I started on COPD Herbal treatment from Ultimate Health Home, the treatment worked incredibly for my lungs condition. I used the herbal treatment for almost 4 months, it reversed my COPD. My severe shortness of breath, dry cough, chest tightness gradually disappeared. Reach Ultimate Health Home via their email at ultimatehealthhome@gmail.com . I can breath much better and It feels comfortable!

30 April 2021 at 14:41

Post a Comment