▶Congenital melanocytic nevi (CMN) are found at birth in about 1% of newborns.
▶Congenital melanocytic nevi have an increased risk of malignant transformation.
■The risk of small (<1.5 cm) and medium (1.5–20 cm) lesions is low (<1% risk over a lifetime—lower than the baseline risk of malignant melanoma).
■The risk of large (>20–40 cm) or “giant” lesions (>40 cm) is higher but less than 5% (and melanoma is most likely in “giant” lesions).
▶Congenital melanocytic nevi usually are present at birth but may appear during the first 6 months.
▶Most lesions are small (<1.5 cm in diameter).
■Typically are larger than acquired nevi (Figure 70.1)
■Usually are slightly elevated and have surface texture changes (Figure 70.2)
▶Occasionally, lesions are large (ie, giant), measuring 20 cm or more, and have significant hair (Figure 70.3).
▶Large and giant CMN are often accompanied by satellite lesions (Figure 70.4).
Look-alikes
Disorder | Differentiating Features |
•Small, hyperpigmented macules located in sun-exposed areas such as the face, upper chest, and back. •Ephelides become darker following sun exposure and may lighten during times of less sun exposure. •Unlike CMN, have no change in surface texture or malignancy potential. | |
•Small, hyperpigmented macules not limited to sun-exposed areas. •Unlike CMN, have no change in surface texture or malignancy potential. | |
Café au lait macules | •Hyperpigmented macules that are not elevated and have no change in surface texture or malignancy potential. |
▶The diagnosis is made clinically based on the history and typical appearance of the lesion.
▶Small CMN that are asymptomatic and not changing may be observed or excised at puberty (malignant change before puberty is extraordinarily rare).
▶Infants who have larger lesions should be referred to a plastic surgeon for discussion of possible excision.
Treating Associated Conditions
▶Due to the risk of central nervous system involvement (ie, neurocutaneous melanosis), in infants with extensive CMN on the head or overlying the midline of the back, and especially in those with large numbers of satellite nevi, magnetic resonance imaging of the brain and spinal cord should be performed.
▶Large congenital nevi are at significantly increased risk of melanoma development and should be considered for removal.
▶Melanoma is the malignant neoplasm of melanocytes that may arise de novo or from preexisting nevi. Consider the possibility of melanoma when a CMN exhibits any of the following ABCDE criteria:
■Asymmetry
■Border irregularity
■Color variation (especially red, blue, black)
■Diameter larger than about 6 mm (but this criterion is less useful for CMN, as they are often larger than this very early after birth)
■Evolving lesion that is changing quickly
▶Patients with CMN that are intermediate or large in size, or which show atypical features, should be referred for dermatologic evaluation.