Moles (melanocytic nevi)
What are the aims of this leaflet?
This leaflet has been written to help you understand more about melanocytic naevi. It tells you what they are, what causes them, what can be done about them, and where you can find out more about them.
What are melanocytic naevi?
The lay term for a melanocytic naevi is a “mole”. The word ‘melanocytic’ means that they are made up of the cells (melanocytes) which produce the dark pigment (melanin) that gives the skin its normal colour. Melanocytes cluster together to form naevi. In other words, moles are localised and benign accumulations of melanocytes.
Some moles (congenital melanocytic naevi) are present at birth. Most come up later (acquired melanocytic naevi). Most people have at least one acquired mole and many people have several moles. Some come up in early childhood, and others come up later, particularly during adolescence and pregnancy. Some even go away in old age.
What causes melanocytic naevi?
Their cause is not fully understood. A genetic factor is likely. Another factor is exposure to too much sun in childhood, as those who grow up in the sunniest countries tend to have the most moles. Moles are most common in people with fair skin.
Are melanocytic naevi hereditary?
A tendency to have many ordinary melanocytic naevi runs in some families. ‘Dysplastic naevi’ (see below), in particular, tend to run in families.
What are the symptoms of melanocytic naevi?
Usually there are none. Some people do not like the appearance of their moles. Raised moles may catch on things. Moles may become sore and inflamed after hairs have been plucked out of them.
What do melanocytic naevi look like?
Those that are present at birth (congenital melanocytic naevi) are seldom less than 1 cm in diameter but can be much larger. They grow in proportion with you as you grow. They are dark and tend to become more raised and hairy with age.
There are three main types of acquired melanocytic naevi:
- Junctional melanocytic naevi are flat, and usually circular. Their colour is usually even, and ranges from mid to dark brown.
- Compound melanocytic naevi are raised brown bumps, most of which are hairy. Some have a slightly warty surface.
- Dermal melanocytic naevi are raised, often hairy, bumps, looking like compound naevi, but are more pale coloured.
In childhood, most moles are of the junctional type. Later in life some become raised and more hairy.
There are several other, less common, types of mole. They include the ‘blue naevus’ (a harmless mole that has a dark blue colour), the ‘halo naevus’ (a mole surrounded by a pale ring which may gradually go away by itself), and ‘dysplastic naevi’ (these are usually multiple, with irregular pigmentation and shape, and run in some families. They have a greater tendency than most moles to change into a melanoma, which is a cancer of moles).
How will melanocytic naevi be diagnosed?
Most moles can be recognised easily by their appearance. If there are any worries over the diagnosis, particularly over the possibility of a melanoma (see below), your doctor will arrange for the mole to be removed and checked in the laboratory. It may occasionally be hard to tell a mole from a ‘seborrhoeic keratosis’ (a harmless dark warty area that is common in older people).
Can melanocytic naevi be cured?
Yes. They can be removed surgically if necessary, but most are best left alone.
How can melanocytic naevi be treated?
There are three main reasons for removing moles:
- The most important reason is doubt about the diagnosis. The mole then has to be checked under the microscope. The main worry is usually whether or not the mole is a melanoma. The changes that suggest this are described in more detail in the British Association of Dermatologists’ information leaflet entitled Melanoma. In brief, they include changes in size (getting bigger), shape (becoming asymmetrical with an irregular ragged edge) or colour (an uneven colour with different shades of black brown or pink). Suggestive symptoms include itching and a tendency to bleed, ooze or crust. melanomas.
- The mole has become a nuisance by catching on clothing or being cut while shaving.
- Cosmetic reasons.
If there is any doubt about the diagnosis, the mole should be cut out completely under a local anaesthetic. Other techniques can be used for moles being removed because of their cosmetic appearance or have become a nuisance. These include shaving the mole off, if it is raised (shave excision) and then touching the raw area left behind with a hot point (cautery).
What can I do?
If you have a large number of moles:
- You should examine your skin monthly for moles that are growing, or changing in the ways described above. If you find any worrying changes, or one that is clearly different from the rest, you must contact your doctor immediately.
- You must also protect yourself from too much sun exposure. This does not mean that you can’t ever go on a sunny holiday again; it just means that you need to be careful to avoid sunbathing and burning. You should cover yourself up and use sun protection creams.
- To cover up wear long sleeves, use a hat when out in the sun, and wear long trousers rather than shorts. Use clothing with a tight weave that will block ultraviolet light.
- Avoid the sun particularly from 10a.m. until 3p.m. when sunrays are the strongest. Seek shade whenever possible.
- Use a high factor sunscreen (minimum sun protection factor 30) on areas you can’t cover. A broad spectrum one is best, as it will block both types of ultraviolet radiation (UVA and UVB). Put it on half an hour before going out and reapply it at least every 2 hours, but don’t use these sunscreens as an excuse to stay out in the sun or not to bother with protective clothing.
- Avoid sun beds and tanning lamps.
Where can I get more information about melanocytic naevi?
Web links to detailed leafets: