What is Melanoma?
Melanoma is a cancer which usually starts in the skin, either in a mole or in normal looking skin. It develops in skin cells called melanocytes. These are cells which produce a pigment called melanin. Melanin helps determine the colour of our skin. Moles are groups of melanocytes that lie close together. Most pale-skinned people have about 20-30 moles on their skin.
What causes Melanoma?
One of the causes of melanoma is ultraviolet (UV) rays from the sun. These damage the skin. People whose skin burns easily are at most risk of developing melanoma – typically people with fair skin, fair or red hair and blue eyes.
Melanoma is very rare in childhood. However, children and young adults who are overexposed to the sun and have severe burning or blistering are at risk of developing melanoma in later life. It is less common in Asian or black people, but more common in women, particularly between the ages of 40 and 60.
The trend to take sunny holidays abroad is leading to an increase in the number of people developing melanoma and other skin cancers. Melanoma and skin cancer are also rising in those who take part in outdoor sports. In some parts of the world, damage to the ozone layer is contributing to the increase in the numbers of people developing melanoma.
Special clothing made of closely woven material can be obtained to protect the skin from the sun. These are particularly useful in protecting children at the seaside. Cotton T shirts offer no protection when wet. A high factor sunscreen (SPF 30 or higher and a minimum of four stars) should be used on any exposed areas of the skin.
If someone in a family develops a melanoma, other family members may be at risk of developing melanoma. Therefore, other close family members should limit their exposure to the sun and report any suspicious moles to their GP. If the GP is concerned that a mole may be suspicious then he/she will refer to a hospital specialist who is experienced at diagnosing and managing melanoma, usually a dermatologist or plastic surgeon. People who have a lot of abnormal moles (known as dysplastic naevus syndrome or atypical mole syndrome) have a higher risk of developing melanoma than other people.
Using sunbeds leads to premature ageing of the skin – wrinkling and liver spots. Sunbeds also increase the risk of developing skin cancer including melanoma. For these reasons, sunbeds should not be used, and it will soon be illegal for those aged younger than 18 years to do so.
Although the number of people who develop melanoma is rising, it is still an uncommon type of cancer.
Types of Melanoma
There are four main types of melanoma which occur in the skin. These are known as cutaneous melanoma:
Superficial spreading melanoma is the most common type of melanoma. About 7 out of 10 (70%) are this type. They occur mostly in middle-aged people. The most common place in women is on the legs, while in men it is more common on the trunk, particularly the back.
They tend to start by spreading out across the surface of the skin. If the melanoma is removed at this stage whilst it is very thin, there is a very high chance of cure. If the melanoma is not removed, it will start to grow down deeper into the layers of the skin. There is then a risk that it will spread in the bloodstream or lymph system to other parts of the body.
Nodular melanoma occurs most often on the chest or back. It is most commonly found in middle-aged people. It tends to grow deeper into the skin quite quickly if it is not removed. This type of melanoma is often raised above the rest of the skin surface and feels like a bump. It may be very dark brown-black or black.
Lentigo maligna melanoma is most commonly found on the face, particularly in older people. It grows slowly and may take several years to develop.
Acral melanoma is usually found on the palms of the hands, soles of the feet or around the toenails.
Other very rare types of melanoma of the skin include amelanotic melanoma (in which the melanoma loses its pigment and appears as a white area) and desmoplastic melanoma (which contains fibrous scar tissue).
Melanoma can start in parts of the body other than the skin but this is very rare. The parts of the body that may be affected are the eye, the mouth, under the fingernails (known as subungual melanoma), the vulval or vaginal tissues or internally.
What are the symptoms of malignant melanoma?
Most melanomas start with a change in the appearance of normal skin. This can look like an abnormal new mole. Less than a third develop in existing moles.
It can be difficult to tell the difference between a mole and a melanoma, but the following checklist can be used to help. It is known as the ABCD list.
Asymmetry – Ordinary moles are usually symmetrical in shape. Melanomas are likely to be irregular or asymmetrical.
Border – Moles usually have a well-defined regular border. Melanomas are more likely to have an irregular border with jagged edges.
Colour – Moles are usually a uniform brown. Melanomas tend to have more than one colour. They may be varying shades of brown mixed with black, red, pink, white or a bluish tint.
Diameter – Moles are normally no bigger than the blunt end of a pencil (about 6mm across). Melanomas are usually more than 6mm in diameter.
Normal moles can be raised up from the skin and/or may be hairy.
Itching, crusting or bleeding may also occur in melanomas – these are less common signs but should not be ignored.
Very few ordinary moles become melanomas but it is best to discuss any changes with your doctor – the earlier melanoma is discovered, the more successful the treatment.