Melanoma is a type of skin cancer. It starts in cells in the skin called melanocytes.
There are 2 main categories of skin cancer. Non melanoma skin cancer (which includes basal cell skin cancer, squamous cell skin cancer and other rare types) and melanoma skin cancer. This page is about melanoma skin cancer.
The skin is a body organ. It 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 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 and the dermis.
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.
Where melanoma starts
Melanoma starts in cells in the skin called melanocytes. These cells are in the deep layer of the epidermis between the layer of basal cells.
Melanocytes make a pigment called melanin. This gives skin its natural colour. The pigment helps to protect the body from ultraviolet light (UV radiation) from the sun.
UV radiation can cause sunburn. This is a sign of damage to the genetic material (DNA) in skin cells. Over time, enough DNA damage can cause cells to grow out of control and lead to cancer.
People who originally come from hotter climates with more sunshine tend to have naturally darker skins. They do not have more of the melanocyte cells than people with pale skin. But their melanocytes are more active and make more of the pigment.
In paler people, the pigment gives you a sun tan. Exposing your skin to the sun makes the melanocytes make more pigment. The pigment is then transferred to the other skin cells to protect them against the sun's rays.
Melanoma can also develop in a mole, or more rarely in areas not exposed to the sun.
Who gets melanoma?
Melanoma may occur at any age, but it is more common in older people. In comparison to most other cancer types, it is also quite common in younger people.
Ultraviolet radiation from the sun or sunbeds is the main environmental factor that increases the risk of developing melanoma.
Other risk factors include:
- skin type
- hair and eye colour
- number of moles
- family history of melanoma
How common is it?
Around 16,700 people are diagnosed with melanoma in the UK each year. The number of people diagnosed with melanoma has increased over the last few decades.
Melanoma is the 5th most common cancer in the UK.