Nevoids are commonly referred to as moles or birthmarks and in the majority of cases are benign proliferations. They are aggregates of cells, melanocytes, which contain a dark pigment called melanin. They appear clinically as small, flat, rounded, slightly raised lesions.

The colour varies from black to light brown depending on the density and distribution of melanin within the cells. Nevoids can be located in any part of the body, on the skin and the mucous membranes, on the conjunctiva (inside of the eyelids) and even on the sclera (the white area of ​​the eye).

Some are present at birth, most of them, however, appear within the first few years of life until puberty. It is also possible for them to appear in adulthood, normally within 40 years of age. Their number depends on hereditary factors and sun exposure. Generally speaking nevoids do not differ much from person to person and this makes it easier to identify those which have significantly different characteristics, what we refer to in medical jargon as an ugly duckling.

On the contrary, nevoids in​children do not need checking frequently. Melanomas before puberty are an extremely rare event, with an annual rate of incidence of 0.8 cases per million in the first ten years of life. On the other hand, considerable attention should be paid to giant congenital melanocytic nevoids in children under 12 as there is a major risk factor of possible transformation. In both cases, the use of dermoscopic tests can help in differentiating between benign pigmented growths and melanomas hence decreasing the number of unnecessary surgical removals of perfectly normal moles. In addition, it provides a safe and simple method of extremely important outpatient screening for the early diagnosis of melanoma in individuals at risk.