Lung cancer is any type of malignant (cancerous) growth in the lungs. There are two main types of lung cancer: non-small cell cancer and small cell cancer. Diagnosis, treatment and prognosis differ for small cell and non-small cell lung cancers. Smoking cigarettes is the number one cause of lung cancer. The lung is the main organ of the respiratory system.Within the lungs and the tracheobronchial system is a lining called the epithelium, and within the epithelium are cells. The function of the cells is to divide, reproduce and repair worn-out or injured lung tissue and to allow for growth. If the cells lose their ability to control division, excess growth takes place, tumors form, and lung cancer emerges.

Causes

Most lung cancer is caused by smoking. Harmful substances in tobacco smoke damage the lung cells. Secondhand smoke is also a risk factor for lung cancer. Besides smoking, exposure to harmful substances such as arsenic, asbestos, radioactive dust, or radon can increase the risk for lung cancer.

A person is "at risk" of developing lung cancer if they:

• Smoke
• Are over the age of 50
• Have or have had a lung disease
• Have a family history of lung cancer
• Have been exposed to secondhand smoke over many years
• Have been exposed to radon

Symptoms

Symptoms of lung cancer vary according to what type of lung cancer you have and where it is located in the lungs. Some symptoms of lung cancer, when and if they occur, are persistent coughing, shortness of breath, blood in the sputum and wheezing.
If the cancer originated and grew in the bronchi and spread to nearby lymph nodes, the symptoms may include:

• Coughing
• Coughing up blood
• Chest pain
• shortness of breath
• Pneumonia
• Hoarseness
• Difficulty in swallowing
• Fatigue
• Loss of appetite
• Loss of weight

Treatment

For non-small cell lung cancer:
Surgery is recommended if the patient is a viable candidate. The stage of the lung cancer and general health determine whether a patient will be considered for surgery. Only 25 percent of lung cancer patients are considered to be surgical candidates at the time of diagnosis.

Chemotherapy and Radiation therapy may be considered after surgery for cancer that has progressed to advanced stages.
Radiation plus Cisplatin-based chemotherapy are recommended if the patient is not a surgical candidate.

For small cell carcinoma:
Combination chemotherapy is typically used to treat the cancer. Surgery is not considered helpful because small cell carcinoma has usually spread at the time of diagnosis. The brain is commonly treated with radiation to treat micrometastases that may have already occurred.

Palliative treatment:
This type of treatment may involve radiation therapy and is geared toward alleviating symptoms, even if the disease is not considered to be curable.
Research about alternative therapies, such as vaccines and immunotherapy, are currently in progress.