the epidermis is the top or outer layer. It contains two main types of cells : squamous cells and melanocytes
the melanocytes produce melanin, the substance that gives skin its colour (pigment). When the skin is exposed to sunlight it gets darker because the melanocytes produce more melanin under this situation.
Types of skin cancer
Basal cell carcinoma (BCC)
BCC is the most common form of skin cancer, making up 70-85% of all skin cancers.
It usually occurs in people over 40 years of age but can develop in younger people.
Most BCCs develop on areas exposed to the sun such as the head, neck and upper body. Some appear on the arms and legs.
BCCs can be red, pale or pearly in colour.
They tend to grow slowly and don't spread to other parts of the body. But if left untreated, BCCs can grow deeper into the skin and damage nearby tissue. This may make treatment more difficult and increase the chance of skin cancer coming back.
Squamous cell carcinoma (SCC)
SCCs are less common and account for about 15-20% of cases. It occurs mostly in people over 50, and usually appears on the head, neck hands and forearms. Less often, it can also develop on the upper body or the legs.
SCCs may appear as thickened red, scaly spots, which later may bleed easily or be tender to touch. SCCs tend to grow quickly overall several months and can spread to other parts of the body. SCCs on the lips or ears have a high risk of spreading and should be seen by a doctor immediately.
Melanoma is the least common skin cancer but the most serious. It accounts for about 5% of cases. It can be treated successfully when diagnosed early.
The first sign of melanoma is usually the appearance of a new spot, or a change in an existing freckle or mole. The change may be in size, shape or colour and is normally noticed over several weeks or months rather than days.