In the human body, there are 2 sponge-like organs found in the chest called lungs. The lungs help in inhaling and exhaling of air in and out of the body, taking in oxygen and getting rid of carbon dioxide gas, a waste product.

The lining around the lungs, pleura, protects the lungs and allows them to move during breathing. The windpipe (trachea) brings air into the lungs and divides into tubes called bronchi, which divide into smaller branches called bronchioles. At the end of these small branches are tiny air sacs known as alveoli where carbon dioxide and oxygen exchange takes place.

Lung cancer, a malignant tumour of the lungs, is the leading cause of cancer deaths in the United States, amongst both men and women. It has claimed more lives than colon, prostate, lymph and breast cancer combined. The most important risk factor for lung cancer is tobacco smoking.

The beginning of most lung cancers is the lining of the bronchi, though they may start in other parts of the lung. Generally, lung cancer takes many years to develop. To begin with, there may be areas of pre-cancerous changes in the lung. These can?t be seen on an x-ray and they don?t cause any symptoms. However these changes can be detected by certain special tests of cells in the lining of the airways of lungs damaged by smoke. Slowly these pre-cancerous areas develop to become true cancer. They make chemical changes that cause new blood vessels to form nearby. The cancerous growth takes nourishment from these vessels and develops into a tumor. Once lung cancer has occurred, cancer cells start breaking away and spread to other parts of the body in a process called metastasis. Lung cancer is a life-threatening disease because it spreads in this way.

Lung cancer is often advanced by the time it is diagnosed as it shows minimal symptoms in the beginning. The most common symptom is cough, which occurs when a tumor irritates the lining of the airways or blocks the passage of air. In addition to cough, other symptoms could be:

• Smoker's cough
• Blood in cough, even a small amount
• Chest pain
• Shortness of breath
• New onset of wheezing
• Repeated bouts of pneumonia or bronchitis
• A hoarseness that lasts more than two weeks

Lung cancer may cause fatigue, loss of appetite and weight loss. If it has spread to other parts of your body, headaches or bone pain can also be a symptom.

Smoking and lung cancer go hand in hand. Thus quitting smoking is the best prevention for lung cancer. Few other measures include ?