Skin cancer is the uncontrolled growth of abnormal cells in the skin. Cancer that only affects cells in the skin's top layer is called superficial cancer. Cancer that spreads deeply into the skin or to other parts of the body is known as invasive cancer.
There are three main types of skin cancer: basal cell carcinoma (BCC), squamous cell carcinoma (SCC) and melanoma. There are other rare skin cancers, such as those that start in the sweat glands and hair follices.
BCC makes up about 70% of non-melanoma skin cancers.
BCCs tend to grow slowly and don't usually spread to other parts of the body. However, if BCC is left untreated or grows larger than 5cm, it may grow deeper into the skin and damage nearby tissue. This may make treatment more difficult and increase the chance of the BCC returning.
SCC accounts for about 30% of non-melanoma skin cancers.
SCCs tend to grow quickly over several weeks or months. It is possible for SCCs to spread to other parts of the body - SCC on the lips, ears, scalp or temples has a high risk of spreading and should be seen by a doctor immediately.
Bowen's disease is an early skin cancer that is often called squamous cell carcinoma-in-situ. The SCC cells are confined to the epidermis, and they usually appear as a red scaly patch.
Melanoma is the least common type of skin cancer but is the most serious. Normal, healthy freckles or moles usually have a smooth edge and an even colour. Melanoma often has an irregular edge or surface, and it may be blotchy and brown, black, blue, red, white or light grey.
Left untreated, a melanoma may spread deeper into the skin where cancer cells can escape and be carried in lymph vessels or blood vessels to other parts of the body.
For information about melanoma, call the Cancer Council Helpline on 12 11 20 for a free copy of the Understanding Melanoma booklet.
A freckle or mole that itches, bleeds or becomes larger or irregular in shape may be a melanoma and should be seen by a doctor without delay.
Last Reviewed: 01 March 2011