Although cutaneous melanoma is rare in children, congenital nevi are one of several known risk factors for melanoma.
Congenital melanocytic nevi (CMN) found on newborns can carry a low risk of melanoma or a much higher risk, depending on their size.
The ability to understand the myriad differences between and risk factors associated with small, intermediate, large and giant nevi can be crucial to proper diagnosis and treatment, according to Hanspaul S. Makkar, M.D., department of pediatric dermatology at the University of California, San Francisco.
"First of all, there's a problem with defining pigmented lesions and categorizing them," Dr. Makkar tells Dermatology Times. "Congenital melanocytic nevi are defined as benign nevomelanocytic proliferations that are present at birth. Large and giant nevi are always present at birth, but rarely will small 'early-onset nevi' or 'nevus tardive' appear between the ages of 1 month to 2 years. The features are indistinguishable clinically or histologically from truly congenital nevi, so therefore, they are treated identically to them."
Although cutaneous melanoma is rare in children, congenital nevi are one of several known risk factors for melanoma. A review of recent research on the topic sheds light on the link between lesion size and melanoma risk.
Although the risk of malignant transformation in small congenital nevi is controversial, some estimates have put it at 2.6 percent to 4.9 percent for people who live to age 60, with the risk being essentially post-pubertal. A recent study that followed 232 patients with CMN for 25 years failed to detect an association between small to intermediate-sized nevi and melanoma risk.
Although experts have not reached consensus on the management of small nevi, "The pre-pubertal risk of melanoma for those with small congenital nevi appears to be very low," Dr. Makkar says. "So our approach is lifelong observation for small, banal-appearing nevi. We reserve excision for irregular nevi and those in difficult-to-follow locations. (Excision) ... is usually postponed until after puberty."
Medium-sized nevi pose some increased risk of melanoma, but data is insufficient and management of lesions of this size remains controversial.
Large CMN are sporadic and often display pigmentary and textural irregularities. Over time, phenotypic changes occur, which include lightening or darkening, thickening and hypertrichosis and nodularity.
A very real risk of melanoma exists in giant nevi - upwards of 10 percent over a lifetime. The risk is greatest in early childhood and through the first decade of life, suggesting that early intervention can be important. In addition, other malignancies can arise in these large lesions. Surgical removal cannot completely eliminate the risk of melanoma in giant nevi, possibly because of deep infiltration of nevus cells beyond fascia, and even into the central nervous system.
"The extracutaneous sites may be more at risk for the development of melanomas," Dr. Makkar says, "so, in addition to visual inspection, palpation and imaging may be invaluable."
Management options for giant nevi include staged excision with grafting and tissue expansion; dermabrasion/curettage; and ruby laser.
However, according to Dr. Makkar, "There are currently no satisfactory options. Ultimately, the management of nevi should be based on several factors. We need to look at the perceived risk of melanoma and the patient's age. Consider the cosmetic outcome, the location of the nevus, the risk of anesthesia and the surgical complexity. All of these things are important considerations."
To support his views, he cites these statistics: