SCOTTSDALE, ARIZ. — Although childhood malignant melanomas are rare, physicians must keep an eye out for them, Ronald C. Hansen, M.D., said at a pediatric update sponsored by Phoenix Children's Hospital.
About 2% of all melanomas appear in children, but the types that commonly occur in children are different from those found in adults. Melanomas in children arise from congenital nevi, de novo nodular nevi, and superficial spreading melanomas that are sun induced, said Dr. Hansen, a dermatologist at the hospital.
Although 70% of melanomas in adults are sun induced, superficial spreading melanomas, about 80% in children arise from congenital nevi or de novo nodular lesions, he said. “There are very, very different concepts of melanoma in childhood.” Congenital nevi that occur in 2% of children arise during the first 4 months of life. Most are small, less than 1.5 cm.
Excision of congenital nevi is not necessary in infancy, but Dr. Hansen suggests that children with nevi be followed closely. “In children, these are more important than the other moles.”
Melanomas in small congenital nevi usually occur at or after puberty, he said. “I recommend prophylactic excision at age 10 in girls and at age 13 in boys, especially if the nevi are on the scalp, face, or trunk. This is a treatment strategy. It's not necessarily what everyone else advocates.”
Giant nevi in children and those over 6 cm in a newborn, have a 5%–8% melanoma risk. Many of these nevi are too large to totally excise. However, Dr. Hansen recommends prophylactic excision in the areas of highest risk, such as the head, spine, and midline of the back.
The second most common type in children is nodular melanoma, constituting 40% of the melanomas in childhood. The nodules are rapidly growing and a red, bluish purple in color. They often ulcerate and, at times, bleed.
This is a highly fatal type, he said. The nodules are thick at the time of diagnosis.
And, in third place are the superficial spreading malignant melanomas. Here the ABCD rule applies: asymmetry, border irregularity, color variation, and diameter over 6 mm. However, the idea that the lesion in a child has to be more than 6 mm is not reality, Dr. Hansen said.
“This is increasing because of the sun exposure of kids,” he said.
Melanomas start out as a speck, and only 20%–40% start in preexisting moles, he said. About 60%–80% start in de novo moles. “It's the new kid on the block, the new mole that can get you into trouble,” he said.
All nevi have some potential to develop melanoma, but it is very low, Dr. Hansen said. “Congenital and dysplastic nevi have the most potential.”
Dysplastic or atypical nevi, once considered precursors of melanoma, are so common that the predictive value is less than once thought, Dr. Hansen said.
These nevi look very similar to melanoma. Usually, they are over 5 mm in diameter, have color variegation, and have fried-egg morphology with a central papule and red/tan halo. The borders are not clearly defined. These occur in 50% of affected whites; one or two of these probably means very little, Dr. Hansen said.
However, if a person has more than 100 moles, a family history of melanoma, and several large atypical nevi, there is a 50% chance of melanoma.
“These individuals have to be followed carefully,” he said. “We have seen teenagers that fit this category, and we follow them like a hawk.”
Early recognition and referral is essential, followed by biopsy and surgical excision, he said. Adjunctive therapies have marginal additional value. The depth of the lesion is extremely important, with a depth of less than 1 mm being 95% curable and up to 3 mm being 40% curable.
Dermoscopy has evolved as an essential tool to follow pigmented lesions, he said, adding that high-risk families may need 3-month evaluations and frequent biopsies.
There has been a 20-fold increase in the incidence of melanoma since 1930. “This is about the time that people decided to get stupid and take off their clothes for recreational sun,” he said.
The best prevention is staying out of the sun at its highest intensity, wearing protective clothing, and applying sunscreens, he said. “We need an outbreak of common sense.”