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Naevi or Moles

Why are some people born with moles while others develop them later in life?

Moles or Naevi are benign growths on the skin. Skin cells called melanocytes produce pigment that gives skin its natural colour. Moles develop when melanocytes grow in a cluster. Moles often darken after exposure to the sun, during the teen years, and during pregnancy. They appear singly or in groups anywhere on the body.

Although most moles develop in early childhood and during the first 20 years of life, others do not appear until later in life. It is quite normal to have anything up to 40 moles by adulthood. While some moles slowly fade over time, others change slowly, becoming raised and lighter in colour. Often, hairs develop on the mole. Moles that appear at birth are known as congenital naevi. These occur in about one in 100 people and are more likely to develop into melanoma than are moles that appear after birth.

Moles that are larger than the size of a pencil rubber and irregular in shape are called dysplastic naevi. These types of moles tend to be hereditary. People with dysplastic naevi might have more than 100 moles and have a greater chance of developing malignant (cancerous) melanoma.

Should I keep an eye on my moles and, if so, what should I be looking for?

Most moles are benign but should be routinely monitored. Seek medical advice if you notice any changes in a mole or if they bleed, become itchy, are painful or appear scaly. When examining your moles, use a mirror or ask someone to help you. Pay particular attention to areas that are often exposed to the sun. What you are looking for is change in size, shape and colour. Check for asymmetry – does one half of the mole match the other half? Look at the edges of the mole – are they ragged, blurred or irregular? Is the colour of the mole the same throughout? Monitor the diameter of a mole and check if it appears raised or elevated.

If your doctor thinks a mole needs further evaluation, he will carry out a biopsy – a small tissue sample of the mole to be examined under a microscope. If the mole is found to be cancerous, the entire mole will be removed by cutting out the mole and a section of normal skin around it.

The wound will then be closed with small stitches. Some people may elect to have unsightly moles, which are completely normal, removed for cosmetic reasons.