Lung cancer is the uncontrolled growth of malignant (cancerous) cells in lung tissue and can be caused by numerous environmental carcinogens, exposure to asbestos and radon gas, scarring from a previous lung disease (e.g. tuberculosis), family history of lung cancer and past cancer treatment.
The tissues of the lung, like the rest of the body, are made up of cells. Normally, these cells divide and grow in an orderly and controlled way as part of the normal growth and repair process. But sometimes the body's control mechanisms get damaged and cells grow and divide in an uncontrolled way forming a mass of tissue called a tumour.
In lung cancer the tumour starts as a small cluster of cells in the lungs.
There are two main types of lung cancer:
- Small-cell lung cancer (SCLC);
- Non-small cell lung cancer (NSCLC).
They are differentiated based on how they look under a microscope. NSCLC is the most common form of lung cancer, making up about 85 – 95% of all lung cancer cases.
It is important to distinguish between NSCLC and SCLC because the two types of cancer are treated differently. Your doctor will recommend the best course of treatment for your particular type of lung cancer.
How your lungs works
Air enters the lungs through the trachea (windpipe). The trachea divides into tubes called bronchi, which divide into smaller branches called bronchioles. At the end of the bronchioles are tiny air-filled sacs known as alveoli. In the alveoli, air is absorbed into the blood stream and the waste gas filters back, to be breathed out.
Most lung cancers start in the bronchi, but they can also begin in other areas such as the trachea, bronchioles or alveoli.