What is Pediatric Melanoma?

Guest blog by Vernon Sondak, MD and Jane L. Messina, MD from the H. Lee Moffitt Cancer Center and Research Institute in Tampa, Florida. Dr. Sondak will be presenting at our 2020 Virtual Pediatric Melanoma Summit. 

Pediatric melanoma is defined as a malignant melanocytic lesion (meaning arising from the pigment-producing melanocyte cells found in the skin and a few other places in the body) occurring in a child at any point from birth to age 18 to 21, depending on the cutoff employed for defining adulthood. Typically, we consider pediatric cases to be under age 18, with cases between 18 and 21 considered as “young adults.” We classify pediatric melanoma according to the age at diagnosis: congenital (present at birth), infantile (diagnosed in the first two years of life) and prepuberty childhood versus postpuberty adolescence. Pediatric melanoma can also be categorized based on the appearance under the microscope, which we refer to as the histologic subtype, and by the presence or absence of precursor lesions like a birthmark or mole. Also, the standard clinical and pathologic staging criteria used for adult melanoma cases can be applied to pediatric melanoma.

Relatively few pathologists are experts in diagnosing moles and melanomas in children as opposed to adults. Even expert pathologists often have difficulty knowing for sure whether or not a biopsy of a melanocytic lesion is definitely malignant. There are a number of melanocytic lesions that are difficult or impossible to reliably categorize as benign or malignant using currently available criteria. We use the term “atypical melanocytic neoplasm” for these difficult to classify lesions, and the pathologist tries when possible to further subclassify these atypical lesions based on their microscopic appearance to give the treating physician an estimate of the potential for recurrence and metastasis. If your child’s biopsy result is not definitive, don’t hesitate to ask for a second opinion from a pathologist specializing in pediatric melanoma cases. In children, skin biopsies are often small and only partially sample the lesion. Sometimes, more information is available when the entire lesion is removed, so complete removal is often required in cases of diagnostic uncertainty. Other specialized tests, such as FISH and CGH, can be used to supplement the information that the pathologist gets under the microscope. These tests can sometimes help the pathologist, but generally are not definitive in determining whether something is or is not melanoma. These tests may not be covered by insurance, so be sure you understand what testing is being ordered and how it might be used.

Normal (noncancerous) moles start to appear in childhood and continue to develop through the teen years, into adulthood. So just because your son or daughter has a new spot on their skin, it does not mean they have melanoma. You can minimize the number of moles your child will get by protecting them from excessive sun exposure and especially sunburns, but nothing can prevent all moles from occurring. If “funny looking” (dysplastic) moles run in your family, there’s a good chance one or more of your children will have similar moles. So, when is a mole considered worrisome in a child?

Most pediatric melanomas don’t follow the standard ABCD rules we use for adult melanoma detection, but some do. In adults, Asymmetry, Border irregularity, Color changes and a Diameter >6 mm (the size of the eraser on the tip of a pencil) aid in the detection of most melanomas. Only a minority of melanomas in young children follow these rules – but we don’t want to miss those cases either. For the rest of the cases, studies have shown that they are frequently Amelanotic (not darkly pigmented), Bumps that may be Bleeding, uniform Color and Developing from normal skin rather than a preexisting mole. So there may actually be two different sets of ABCD rules, one that is more appropriate for adult-type melanoma and the other that is more appropriate for children.

You know your child’s skin better than anyone. Regardless of the “rules,” if something seems wrong on your child’s skin, get it checked out. And if a skin lesion continues to grow, consider having it biopsied or removed – even if that means getting a second opinion to do so. Be on the lookout for the “ugly duckling,” a mole or other skin lesion that stands out as clearly different in size, shape, color or the rate of its growth compared to all the others. If you see an ugly duckling mole on your child’s skin, get it checked out.

In general, pediatric melanoma seems to have a lower risk of local recurrence and a higher incidence of nodal metastasis when compared to adult melanoma of the same thickness. We always recommend removing a melanoma or atypical melanocytic neoplasm with a margin of surrounding normal skin – called a wide excision. Generally, a margin of 1 cm (less than ½ an inch) of surrounding skin is sufficient, and this typically results in a scar that is about 6 to 8 cm (2 ½ to 3 inches) long. The role of sentinel lymph node biopsy in children is a hotly debated topic, but we use it routinely in pediatric melanomas that are thick enough to possibly spread to the nodes (the typical cutoffs used are 0.8 mm or 1 mm in thickness as measured by the pathologist under the microscope). Just as in adults with positive sentinel nodes, we no longer routinely remove all of the lymph nodes in that area. Instead, we carefully follow the involved nodal basin with physical check-ups and ultrasound testing, with further surgery reserved for cases that reoccur within those lymph nodes. Many children with positive sentinel nodes are sent to an adult or pediatric medical oncologist to consider postoperative (also called adjuvant) treatment with immune therapy or molecularly targeted therapy to decrease the chances of recurrence.

Check out www.melanoma.org for more tips and suggestions, and other valuable resources.