Skin cancer is the most common form of cancer in humans. It consists of a malignant growth, which usually develops in the outermost layer of the skin called the epidermis, meaning that a tumour is generally clearly visible. It primarily develops on areas of skin that are exposed to the sun such as the scalp, face, ears, lips, neck, chest, arms and hands. Skin cancer rarely spreads beyond the skin, apart from malignant melanoma (See below).
The epidermis contains three different types of cells:
- Squamous cells – just below the outer surface.
- Basal cells – below the squamous cells, these produce new skin cells.
- Melanocytes – these are in the lower part of the epidermis and give the skin it’s normal colour.
There are three main types of skin cancer:
- Squamous cell carcinoma – about 25% of all skin cancers, this is quite aggressive but rarely spreads to local lymph nodes
- Basal cell carcinoma – 70-75% of all skin cancers, this is the most common. It progresses very slowly but can be destructive to local cells.
- Malignant melanoma – 1-5% of skin cancers – this is a very aggressive tumour and is very often seen with regional and / or distant metastasis (see below)
Skin cancer is more likely to develop in people that show the following risk factors:
- Lighter natural skin colour
- Family or personal history of skin cancer
- Exposure to the sun
- A history of sun burns early in life
- Skin that burns, freckles, reddens easily or becomes painful in the sun
- Blue or green eyes
- Blonde or red hair
- Certain types and a large number of moles