Incidence of pediatric melanoma on the rise

Banff, Alberta - Clinicians have to consider actions to avoid the potential for mortality if melanoma is suspected in pediatric cases, and they should be cognizant that pediatric melanoma cases represent a very heterogeneous group of patients, according to the chairman of the department of cutaneous oncology at the Moffitt Cancer Center, Tampa, Florida.

“There are a growing number of children, some as young as 4, who have melanomas that seem to behave and seem to be identifiably different than what we are used to with adults," says Vernon Sondak, M.D., a surgical oncologist, discussing pediatric melanoma here at the 8th Canadian Melanoma Conference.

But melanoma that occurs in individuals in late adolescence appears more similar to melanoma that occurs in adults, Dr. Sondak says.

The incidence of melanoma is going up in children, especially teenagers, and clinicians such as Dr. Sondak believe the use of tanning beds is implicated in this rising incidence. “The rise (in melanoma) is greater in places that do not have high ultraviolet (exposure) versus areas of the U.S. where there is higher UV,” Dr. Sondak says.

Rising rates of melanoma

A study published last year found that, indeed, melanoma is occurring more often in children. The rate rose about 2 percent in newborns to age 19 from 1973 to 2009. The largest increase was amongst adolescents, ages 15 to 19, particularly girls. Investigators found living in northern latitudes, being female, and being age 15 to 19 were all linked to the greatest spikes in incidence (Wong JR, Harris JK, Rodriguez-Galindo C, Johnson KJ. Pediatrics. 2013;131(5):846-854).

The finding about living in more northern latitudes being associated with the largest increase was of special interest since it points a finger at artificial sources of UV radiation such as tanning beds rather than natural sources. While very rare, neonates can develop melanoma through placental transmission from a mother with widespread melanoma, Dr. Sondak says.

“It is extremely rare, but it can happen,” he says. “Additionally, neonates who are born with a very large congenital ‘bathing trunk nevus’ can develop melanoma in the first year or two of life. Pediatricians now recognize that patients with a bathing trunk nevus are at high risk (of developing melanoma). These infants are watched more carefully, and the nevus removed surgically when appropriate.”

Another observation by Dr. Sondak is that children ages 13 and under who have Fitzpatrick skin types IV, V and VI are being diagnosed with melanoma, and clinicians don’t have an explanation for the phenomenon. It is also clear that melanoma in younger children often fails to demonstrate the classic “ABCDs” that are associated with melanoma in adults. Pediatric melanomas seem to be more often amelanotic, nodular and even verrucous in appearance, Dr. Sondak says.

One possible explanation for the overall increase in pediatric melanoma cases is increased awareness. There has been a rise in pediatric patients having unusual moles biopsied, owing to this increased awareness.

“More of these moles are being biopsied, and more questionable lesions are being put in front of pathologists,” Dr. Sondak says.

‘Diagnostic uncertainty’

Pediatric melanoma represents a challenge to pathologists, and pathologists often label suspected melanoma in children as atypical melanocytic neoplasms, he says.

“Pathologists often have difficulty in definitively diagnosing melanoma in a child such as ‘atypical melanocytic neoplasms’ or ‘melanocytic tumor of uncertain biologic potential,’” Dr. Sondak says. “We have to understand it is a complex situation. There is a degree of diagnostic uncertainty about what the lesion is and how it will behave.”

Given the potential for uncertainty about the prognosis of pediatric melanoma and atypical melanocytic neoplasms, clinicians need to consider making treatment decisions based on what are the worst-case scenarios, Dr. Sondak says.

“We have seen some of the atypical tumors, where the pathologist cannot make a definitive diagnosis, lead to widespread metastatic disease or even death,” he says. “If we have an atypical skin lesion where melanoma that could potentially kill the child is in the differential diagnosis, then we will take precautions to deal with it that are basically the same as when a formal diagnosis of melanoma is rendered. That will mean removing the lesion with a margin of about 1 cm, and when appropriate, checking the sentinel lymph node.”

In some cases where a sentinel lymph node biopsy is not performed, regional nodal ultrasound would be performed, and the child would continue to be followed, Dr. Sondak says.

If the sentinel lymph node is positive, management is generally identical to that for an adult with stage 3 melanoma. Management could include doing a complete lymph node dissection and/or giving the patient interferon, according to Dr. Sondak.

“Children tolerate interferon better than adults tolerate it,” he says. "No one wants to over-treat, but the uncertainty (of a diagnosis) should be acknowledged and addressed head-on.”

Disclosures: Dr. Sondak reports no relevant financial interests.