Health News. Lots of resources and information

Moles, better known as pigmented naevi, are benign tumours of the skin. They arise as a localized abnormality of the pigment cells in the skin. Moles are uncommon at birth, and their incidence increases throughout childhood, reaching a peak at about puberty, and gradually declining with increasing age. Moles are common in all races and in both sexes. The average number per person in adolescence is about 20. They frequently increase in number during pregnancy. By the age of 70, however, very few moles remain.

The natural history or evolution of moles is both interesting and important. The earliest, or youngest type of mole, is the junctional naevus. This is situated completely within the epidermis, at the junction of the epidermis with the dermis. It appears as a flat, brown-black mark without any substance to it. The border is usually irregular, but normal skin markings are visible through it. By a process of maturation termed ‘dropping off, cells begin to appear within the dermis.

The mole is then termed a compound naevus. It appears as a raised, brown-black lump with, on occasions, a coarse hair projecting from it. As the mole ages, more and more cells appear in the dermis and eventually, as seen in older people, there is no cell activity in the epidermis. The mole has now developed into an intra-epidermal naevus. These naevi appear more regular in outline, frequently raised, but much less pigmented than compound naevi. The maturation process continues and eventually, in old age, there is disintegration of the mole which is replaced by fibrous tissue forming a skin tag; this may simply drop off.

However, if a mole is subjected to certain stimuli-as yet unknown-it may not undergo this usual ageing process; instead, at any level of maturation, it may develop into a malignant melanoma. It must be stressed, however, that only ;about one mole in every 500000 becomes malignant. Only about 25 per cent of malignant melanomas arise from a preceding mole.

*72\44\4*