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INTRODUCTION TO CHAPTER
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Melanocytic nevi (moles) are common benign skin tumors. In most people, these are primarily of cosmetic significance. However, nevi can occasionally become irritated or subjected to trauma and may need to be removed for this reason. Atypical nevi are considered benign, but they have some features that resemble melanoma and can be a marker for the increased risk of developing melanoma.
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Melanoma is a potentially deadly cancer of melanocytes whose incidence is on the rise. It is unique among most serious cancers, because it can be detected by both patients and clinicians with a simple skin examination. When detected at early stages, melanoma is very treatable. Recognition of early melanomas by both patients and clinicians is key.
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Melanocytic nevi (moles) are among the most common benign tumors in humans. White individuals tend to have higher numbers of nevi than other populations. When nevi are present in Asian and Black individuals, they are more likely to be on the palms and soles. Interestingly, nevi are also less common in patients with light skin tones with the melanocortin-1 receptor (MC1-R) gene pigment variant (Fitzpatrick type I: red hair, fair skin, always burns, never tans skin type).1
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Nevi begin to appear in early childhood, reach a maximum number in the 3rd to 4th decade of life, and then subsequently decline in number.2 Genetic factors likely play a role in a person's potential for development of nevi and total nevi counts in adulthood. Nevi are more common on sun-exposed skin, as natural sunlight and artificial ultraviolet light are factors in their induction.
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Melanocytic nevi can be subdivided into two major categories: congenital and acquired.
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CONGENITAL MELANOCYTIC NEVI
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Key points for congenital melanocytic nevi
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✓ Congenital melanocytic nevi are present in 1% of Caucasian infants at birth and have no gender predilection.
✓ They represent as tan, brown or black plaques usually ranging in size from <1 cm to >20 cm.
✓ The lifetime risk of developing melanoma in all sizes of congenital melanocytic nevi is estimated to be only 1-2%. However, in giant congenital melanocytic nevi with multiple smaller satellites, the risk is estimated to be as high as 10-15%.
✓ Patients with large and giant congenital nevi should be referred to dermatology for evaluation and long-term monitoring of their nevi.
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Our understanding of congenital melanocytic nevi has recently evolved and now two variants are recognized: those present at birth and those that develop before puberty. Congenital melanocytic nevi are present in 1% of White infants at birth and have no gender predilection. Congenital melanocytic nevi present at birth are highly variable in size and appearance, ranging from millimeters in size to occupying up to ...