There are 2 main types of skin cancer. Non melanoma skin cancer that includes basal cell skin cancer, squamous cell skin cancer and other rare types. The second is melanoma skin cancer.
This section is about non melanoma skin cancer.
The skin and what it does
The skin does several jobs including:
- protecting the inside of the body from damage
- helping to keep our body temperature more or less the same
- getting rid of some body waste products through sweat
- making vitamin D (this helps form and maintain our bones)
The skin is made up of 2 main layers: the epidermis on the outside and the dermis beneath.
The thickness of the epidermis and the dermis varies depending on the part of the body the skin is covering. For example, the skin on the soles of your feet is quite thick, with an epidermis and dermis of about 5mm. The skin on your eyelids is much thinner, about 0.5mm.
The cells of the skin
Sun damage is the cause of most skin cancers. The cells in the epidermis are most at risk of sun damage.
The most common type of cells found in the epidermis are called keratinocytes. Basal cells are a type of keratinocyte found at the bottom of the epidermis. The basal layer is where all normal skin cells come from, and where basal cell cancer (BCC) develops.
BCC is the most common type of skin cancer. It mostly develops in areas of skin exposed to the sun such as the head, face, ears and neck.
The top two layers of the skin are made up of cells that have died and pushed up from the basal layer. They're filled with keratin made from keratinocytes. It's a tough waxy substance that helps to make the skin strong to protect the body.
Squamous cell cancer (SCC) also develops from keratinocytes in the epidermis. These develop in the cell layer just above the basal layer.
Melanoma skin cancer starts in the skin cells called melanocytes. These are cells in the deeper layers of the epidermis. Melanocytes make melanin. This is the brown substance that the melanocytes produce when the skin is exposed to the sun.
Skin cancers can grow slowly and it can take some years before a cancer is noticed. But sometimes a skin cancer can grow very quickly, within a few months.
Who gets it?
Most skin cancers are caused by exposure to the sun. This may be long term exposure, or short periods of intense sun exposure and burning. There are several factors that affect your risk from sun exposure including:
- how much time you spend outdoors
- your natural skin colour
Sun exposure can also be in the form of sunbeds (artificial UV radiation). People who use sunbeds are also at risk of developing skin cancer.
Age is also a factor. The older you are, the more likely you are to get non melanoma skin cancer.
How common is it?
Around 147,000 cases of non melanoma skin cancer are diagnosed in the UK each year. The number could be higher as we know that they are under reported. This makes it the most common type of cancer by far. Because non melanoma skin cancers are easy to treat and cure, they're often left out of national cancer statistics.