What is melanoma? Your questions about the skin cancer answered after Sarah Ferguson's diagnosis - including how to check your moles

Sarah Ferguson has been diagnosed with the most serious type of skin cancer - a malignant melanoma.

The Duchess of York, 64, had a mole removed from her body while undergoing breast reconstruction surgery last year, one of which was found to be cancerous.

The cancer occurs after the DNA in skin cells is damaged, triggering mutations that can form malignant tumours - which can be deadly. 

Around 17,000 people are diagnosed with melanoma each year, according to the latest figures published on the Cancer Research UK website. 

There is an annual average of 2,300 deaths from the skin cancer, according to the charity, with it accounting for around 1 per cent of cancer deaths. 

 Here, MailOnline looks at what melanoma is, how to spot it and how to prevent it. 

Sarah Ferguson has been diagnosed with malignant melanoma. Pictured: The Duchess of York at Christmas Morning Service at Sandringham Church

Malignant melanoma is a serious form of skin cancer that begins in melanocytes (file image)

What is malignant melanoma? 

Malignant melanoma is a serious form of skin cancer that begins in melanocytes, cells found in the upper layer of skin that produce melanin, which gives skin its colour.

It is typically caused by harmful UV rays and then not repaired so it triggers mutations that can form malignant tumours.

While less common that other types of skin cancer, it is more dangerous because of its ability to spread to other organs more rapidly if it is not treated at an early stage.

What causes melanoma? 

• Sun exposure: UV and UVB rays from the sun and tanning beds are harmful to the skin.

• Moles: The more moles you have, the greater the risk for getting melanoma.

• Skin type: People with fairer skin have a higher risk of getting melanoma.

• Hair colour: Red heads are more at risk than others.

• Personal history: If you've had melanoma once, then you are more likely to get it again.

• Family history: If relatives have been diagnosed previously,you can be at higher risk.

How do I prevent it?

• Use sunscreen with a high SPF or cover up to avoid sunburn. 
• Avoid tanning outside and using sunbeds 
• Apply sunscreen 30 minutes before going outside.
• Keep babies and children out of the sun.
• Examine your skin every month and visit your GP every year for a skin examination.

How do I check for it?

Check your skin for any unusual changes. Use a mirror or ask a partner or friend to check any areas you cannot see.

In particular, look for: 

• Moles with an uneven shape or edges 
• Moles with a mix of colours 
• Large moles - melanomas often tend to be more than 6mm wide 
• Moles that change size, shape or colour over time

What signs should I look for in my moles?

Cancer Research UK recommends following its ABCDE approach when checking your moles.

A - Asymmetrical - look at the shape of the mole

• Melanomas are likely to have an uneven shape. The two halves of the area may be different shapes.
• This contrasts with normal moles, which are usually symmetrical and have a more even shape.

 B - Border - look at the edges of the mole

• Melanomas are more likely to have irregular edges that might be blurred or jagged.
• This contrasts with normal moles that are more likely to have even borders. 

C - Colour - Look at the colour of the mole

• Melanomas are often have an uneven colour and contain more than one shade, possibly appearing to be black, brown or pink.
• Meanwhile, normal moles are usually even in colour. 

D - Diameter - Look at how wide the mole is

• Most melanomas are more than 6mm in diameter.
• Meanwhile, normal moles are usually about the size of the end of a pencil or smaller.

E -  Evolving - Check it regularly to see if it is changing

• Melanomas can change in size, shape or colour. They may also begin to bleed, itch or become crusty.
• Normal moles, meanwhile, usually stay the same size, shape, and colour. 

It's important to examine your skin every month and visit your GP regularly for a skin examination (file image)

How can melanoma be treated?

Removal

This can be done by removing the entire section of the tumor or by the surgeon removing the skin layer by layer. 

When a surgeon removes it layer by layer, this helps them figure out exactly where the cancer stops so they don't have to remove more skin than is necessary.

Skin grafting

The patient can decide to use a skin graft if the surgery has left behind discoloration or an indent.

Immunotherapy, radiation treatment or chemotherapy

This is needed if the cancer reaches stage III or IV. That means that the cancerous cells have spread to the lymph nodes or other organs in the body.