The lungs are part of the body’s respiratory system. They are made up of a series of airways called bronchi and bronchioles that end in tiny air sacs called alveoli. The lungs allow blood to carry oxygen around the body.
Lung cancer forms within the cells of the lung and usually develops in the lining of the airway.
There are several types of lung cancer, each beginning in a different type of cell in the lung. The two main groups include:
Small cell carcinoma: This type of cancer accounts for about 12 per cent of all lung cancer cases. It usually arises from epithelial cells that line the surface of the middle of the lung. This type of cancer is associated with a history of smoking. Sometimes the cancer will stay confined to the place in the chest in which it originated; this cancer type is described as ‘limited’. Once the cancer has spread it is described as ‘extensive’.
Non-small cell carcinoma: This cancer type accounts for over 60 per cent of lung cancer and is the most common form. It consists of a different group of cancers that tend to grow and spread more slowly than small cell carcinomas. There are three main types of non-small cell carcinomas. They are:
- Squamous cell lung cancer: The most common type of non-small cell carcinomas. Squamous cell lung cancer develops from the cells that line the airways and it is often found near the centre of the lung in one of the main airways.
- Adenocarcinoma: Develops from the cells that line the airways that produce mucus (phlegm). It is often found in the outer areas of the lungs.
- Large cell carcinoma: Called large cell carcinoma because the cells look large and rounded under a microscope. This type of lung cancer does tend to grow rapidly.
While not strictly a lung cancer, mesothelioma is a rare chest and abdominal lining cancer mainly affecting people exposed to asbestos particles.
Although the causes of lung cancer are not fully understood, there are a number of factors associated with the risk of developing the disease. These factors include: tobacco smoking, a family history of lung cancer and previous lung diseases such as lung fibrosis, chronic bronchitis, emphysema, and pulmonary tuberculosis.