What is a mole?
A mole (or melanocytic naevus) is an abnormal collection of pigment cells present within the skin. These cells are known as melanocytes. Moles are extremely common. Most people are born with a few moles and develop others during their lives.

What causes moles?
Most moles are simply the result of a harmless proliferation of the pigment cells within the deeper layer of the skin. A few of these moles, called congenital melanonaevi, are usually present at birth. But most develop spontaneously or are caused by exposure to sunlight and tend to appear on those areas of the skin that catch the most sunlight.

Most of these moles appear during the first 20 years of life, although they may continue to develop into the 30s and 40s. However, the majority disappear with age.

What are the symptoms of malignancy?

• The mole is itchy and painful.
• Increased size or an increasingly irregular appearance, especially at the edges.
• A change in colour, particularly if the mole gets darker or becomes mottled.
• Spontaneously bleeding.
• Satellite pigmented lesions.

How is malignancy diagnosed?

Although most changes in the size, shape and colour of moles are due to a benign, non-cancerous increase in number of pigment cells, any mole that looks unusual should be examined. Your doctor will probably request information on recent changes to the mole along with a family history to assess your risk.

If only mild changes are found, your doctor will usually only need to take a clinical photograph of it. The mole's appearance may be reviewed in a later appointment. But if your doctor is concerned, an excision biopsy will be arranged, if necessary following a consultation with a plastic surgeon or a dermatologist.