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Nevi (management)

4 June 2012, by GROB J.-J. & GAUDY-MARQUESTE C.


• What is a nevus? Nevi, or benign melanocytic tumors, are not limited to “beauty marks” or moles, which implies the notion of a raised lesion; instead, they more often are small, flat, brown or black spots on the skin. Everyone has nevi, ranging from just a few to over a hundred. Most nevi appear in childhood but their final number depends on genetic factors and sun exposure, especially during the first decades of life. Some nevi eventually disappear over the course of a lifetime and new ones may appear.

• From nevus to melanoma: In the majority of cases, melanoma does not arise from a nevus. Therefore, it makes no sense to remove loads of nevi in order to one day avoid developing melanoma. This is an unnecessary measure which would also be extremely costly.

Indeed, the transformation of a nevus is a very rare event: we all have a large number of nevi (from 5 to over 100) but only one person in 10,000 will develop melanoma each year. The transformation rate is estimated at 1 in 20,000 in men and 1 in 20,000 in women.

The only nevi with a high risk of becoming melanoma are congenital melanocytic lesions. Large nevi ranging in size from 5 cm across to covering large areas of the body are very rare. They are often already present at birth (congenital) or appear early in life. The transformation rate is probably related to the size of the lesion. Giant nevi and those overlying the spine are at higher risk of degeneration which may occur on the skin but also within a possible nevus component in the central nervous system. For so-called “giant” nevi, rapid referral to a dermatologist as soon as possible after birth is essential. 

 • Nevi as indicators of melanoma risk: Individuals with an exceptionally high number or atypical (irregular) appearance of their nevi have a high lifetime risk of developing melanoma.

The general profile of an individual’s nevi (nevus phenotype), that is to say, the number and appearance of the nevi, is a good indicator of that individual’s risk of developing melanoma. This is because this general profile is probably a good reflection of the state of the melanocytic system, which results from both genetic factors and sun exposure.

An individual with many nevi, especially when large or with morphologically irregular features, can be considered to have a particularly high lifetime risk of developing melanoma and should undergo surveillance. Such individuals should be advised to see their primary physician or dermatologist for an opinion. The same is true for individuals with a family history of multiple nevi.

• How to detect melanoma among thousands of nevi: The great majority of brown or black spots are nevi or, in subjects aged over 50 years, seborrheic keratosis. Nonetheless, vigilance is required because an early melanoma may initially resemble these benign lesions. One cannot afford to detect this melanoma when it’s too late, at which point it may have already metastasized.

 Know when to see a doctor in situations where a lesion thought to be a “nevus” might actually be a melanoma:

– A “nevus” which rapidly changes appearance (shape, size, color) with a few weeks or months;

– A new “nevus” that recently appeared after childhood or adolescence;

– A “nevus” that gets irritated or bleeds after a minor trauma, or becomes inflamed or itchy;

– A “nevus” that does not look like the others (“ugly duckling”). Everyone has his own specific nevus profile. A lesion is all the more suspicious when it is different from the other nevi.

 • Therefore, everyone should monitor their nevi and those of the people dear to them.
It should also be noted that many melanomas do not resemble a nevus at all, but this will be discussed in another chapter.

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