Lung cancer originates from tissues of the lung, usually from the cells lining of the air passages. The two major types are small cell lung cancer and non-small cell lung cancer. These types are diagnosed based on how the cells look under a microscope. More than 80°/o of ail lung cancers belong to the non-small cell type. The 3 main sub-types of non-small cell lung cancer are adenocarcinoma, squamous cell carcinoma and large cell carcinoma.

What causes it?
Doctors cannot always explain why one person develops lung cancer and another does not. However, we do know that a person with certain risk factors may be more likely than others to develop lung cancer.
Tobacco smoke is by far the most important and the main risk factor for lung cancer. It is responsible for more than 80°/o of all lung cancer worldwide. Harmful substances in smoke damage lung cells.

Over time, the damaged cells may become cancerous. This is why smoking cigarettes, pipes, or cigars can cause lung cancer. Inhaling such secondhand smoke can also cause lung cancer in nonsmokers. The more a person is exposed to smoke, the greater the risk of lung cancer.

Other risk factors for lung cancer include radon (a radioactive gas), asbestos, arsenic, chromium, nickel and air pollution. People with family members who had lung cancer may be at slightly increased risk of the disease. People who have had lung cancer are at increased risk of developing a second lung tumor. Most people are older than 65 years of age when diagnosed with lung cancer.

Symptoms
Early lung cancer often does not cause symptoms. But as the cancer grows, common symptoms may include:
A cough that gets worse or does not go away
Breathing trouble, such as shortness of breath
Constant chest pain
Coughing up blood
A hoarse voice
Frequent lung infections, such as pneumonia
Feeling very tired all the time
Weight loss with no known cause

Most often, these symptoms are not due to cancer. Other health problems can cause some of these symptoms. Anyone with such symptoms should see a doctor to be diagnosed and treated as early as possible.

Screening
Screening tests may help doctors find and treat cancer early. Several methods of detecting lung cancer have been studied as possible screening tests. These methods include tests of sputum (mucus brought up from the lungs by coughing), chest x-rays, or spiral (helical) CT scans.

You may want to talk with your doctor about your own risk factors and the possible-benefits and harms of being screened for lung cancer. Like many other medical decisions, the decision to be screened is a personal one. Your decision may be easier after learning the pros and cons of screening.

Diagnosis
If you have a symptom that suggests lung cancer, your doctor must find
out whether it originates from cancer or other health conditions. You
may be required to do some blood tests and diagnostic procedures:
Physical Examination
Chest X-ray
Computed Tomography (CT) Scan
Your doctor may order one or more of the following tests to collect samples:
Sputum cytology: Thick fluid (sputum) is coughed up from the lungs. The lab checks samples of sputum for cancer cells.
Thoracentesis: The doctor uses a long needle to remove fluid (pleural fluid) from the chest The lab checks the fluid for cancer cells.
Bronchoscopy: The doctor inserts a thin, lighted tube (a bronchoscope) through the nose or mouth into the lung. The doctor may take a sample of cells with a needle, brush, or other tool. The doctor also may wash the area with water to collect cells in the water.
Fine-needle aspiration:  The doctor uses a thin needle to remove tissue or fluid from the lung or lymph node.
Open biopsy: In cases where the tumor tissue is difficult to obtain, direct biopsy of the lung tumor or lymph nodes through an incision in the chest wall may be needed.

How is lung cancer assessed?
To plan the best treatment, your doctor needs to know the type of lung cancer and the extent (stage) of the disease. Staging is a careful attempt to find out whether the cancer has spread, and if so, to what parts of the body. Lung cancer spreads most often to the lymph nodes, brain, bones, liver, and adrenal glands.

Stages of small cell lung cancer
Doctors describe small ceil lung cancer using two stages:
Limited stage: Cancer is found only in one lung and its nearby tissues.
Extensive stage: Cancer is found in tissues of the chest outside of the lung in which it began. Or cancer is found in distant organs.

Stages of non - small cell lung cancer
Occult stage: Lung cancer cells are found in sputum or in a sample of water collected during bronchoscopy, but a tumor cannot be seen in the lung.
Stage 0: Cancer cells are found only in the innermost lining of the lung. The tumor has not grown through this lining. A Stage 0 tumor is also called carcinoma in situ. The tumor is not an invasive cancer.
Stage I: The lung tumor is an invasive cancer. It has grown through the innermost lining of the lung into deeper lung tissues. Cancer cells are not found in nearby lymph nodes.
Stage II: The lung tumor may be of any size but has not invaded surrounding organs. Cancer cells are found in nearby lymph nodes.
Stage III: The lung tumor has either spread to the nearby organs, chest wall, diaphragm, big vessels or lymph nodes on the same/opposite sides of the tumor.
Stage IV: Malignant growths may be found in more than one lobe of the same lung or in the other lung. Cancer cells may be found in other parts of the body, such as the brain, adrenal gland, liver, or bone.

Treatment for lung cancer
Depending on the stage of the lung cancer, the aims of treatment may be for cure, control of disease for prolongation of survival or management of symptoms and prevention of complications to improve quality of life. The following treatment modalities may be used singly or in combination.

Surgery - Surgery for lung cancer involves the removal of tissues that contain the tumor and nearby lymph nodes.

Radiation Therapy - Radiation therapy (also called radiotherapy) uses high- energy rays to kill cancer cells. It affects cells only in the treated area.

Chemotherapy - Chemotherapy uses anticancer drugs to shrink/kill cancer cells. The drugs enter the bloodstream and can affect cancer cells all over the body.

Targeted Therapy - Targeted therapy uses drugs to block the growth and spread of cancer cells. The drugs enter the bloodstream and can affect cancer cells all over the body. Some people with non-small cell lung cancer that has spread receive targeted therapy.
Source:ParkwayHealth