Approximately 20% of childhood melanomas occur with other melanocytic lesions. Malignant melanomas from small CMN typically occur after puberty. These are more similar to adult malignant melanomas.
Childhood melanomas are associated with an increased incidence of amelanotic and nodular lesions. Risk factors include the following: intermittent intense sun exposure, tendency to sunburn, tendency to freckle, fair skin, blue/green eyes, blonde/red hair, xeroderma pigmentosum, giant CMN, dysplastic nevus syndrome, atypical nevi, a family history of malignant melanoma, and immunosuppression.
The risk of transformation for CMN is associated with size. Small to medium CMN (less than 20 cm) have a 1%-5% risk of transformation, while large/giant CMN (greater than 20 cm) have at least a 5%-10% risk; however, the risk may be as great as 20%.
Some studies suggest that 30%-75% of pediatric malignant melanoma originated in giant CMN, and one-third are fatal, reported Dr. Dyer. Excision does not completely eliminate the risk. In one study, 8% of patients developed extracutaneous malignant melanoma after CMN excision.
He noted that the risk of childhood melanoma is associated with immunodeficiency. The risk is six times greater if immunodeficiency is genetic in origin; the risk is four times greater if immunodeficiency is acquired.
The indications for sentinel lymph node biopsy in children are the same as in adults, he noted. Children have a higher incidence positive sentinel lymph node. However, this does not predict likelihood of recurrence or prognosis in children.
Surgical excision should use the same margins as in adults whenever possible. Thickness, ulceration, and stage at diagnosis are all prognostic factors.
Disclosures: Dr. Dyer reported having no conflicts of interest. SDEF and this news organization are owned by Elsevier.