Sun, kids, moles, and melanoma

Sun, kids, moles, and melanoma

By Joseph G. Morelli, MD, and William L. Weston, MD

Publicity about an increase in melanoma has some parentspanicked. Pediatricians can set these concerns at rest, as well as theirown, with a clear understanding of when a mole suggests melanoma and therole of sunlight in melanoma development.

With the approach of the sunny days of summer, pediatricians and parentsbegin to worry about sun-damaged skin and melanoma. Annual incidence ofmalignant melanoma in the United States and worldwide is increasing at analarming rate.^1,2 Major publicity campaigns encourage parentsto have their children's pigmented nevi checked and urge them to use sunscreenevery day.³ Some parents take their child to the pediatricianbecause a mole has changed, while others even ask that all their children'smoles be removed. To calm these fears, pediatricians need to take a rationalapproach to management of acquired and congenital moles. This calls forknowing which children are at risk for melanoma, how to differentiate suspiciousmoles from those that are benign, when to remove moles, and how to instructfamilies on prevention.

Types of melanoma

Although many authorities regard melanoma as a spectrum of one disease,it has been classified into four types for epidemiologic purposes.⁴These types are superficial spreading melanoma, lentigo maligna melanoma,acral lentiginous melanoma, and nodular melanoma. Superficial spreadingmelanoma is the type associated with acquired nevi and accounts for 75%of all malignant melanomas.^1,2 Most of the data we have fromlarge epidemiologic studies about the relationship of sunlight and melanomarelates to this type. Our review focuses on detection and prevention ofsuperficial spreading melanoma.

Risk factors

Melanoma is increasing in adolescents and adults more quickly than anyother cancer.^5­7 It is not increasing in prepubertal children,in whom it remains rare.^6,7

Exposure to sunlight is the best-known and most studiedrisk factor formelanoma.^1,2,4,8 Individuals with red hair and freckles who uselittle sun protection have the highest risk. Both blistering sunburns andintermittent intense sun exposure in childhood are considered major riskfactors.^2,4,8 The damage to melanocyte DNA induced by ultravioletlight is believed to be responsible. In Australia, a rapid increase in superficialspreading melanoma among adolescents and young adults has been attributedto excessive sun exposure in a population that is predominantly fair-skinned.⁹Tanning lamps are associated with melanoma as well.¹⁰

Although melanomas also develop in skin that has not been exposed tosunlight and in dark-skinned individuals who do not sunburn, a careful historyof sun exposures should be a part of every mole evaluation.^1,2Table 1summarizes the risk of melanoma by skin type.

Many pigmented nevi. Increased sun exposure also leads to an increasein pigmented nevi--another risk factor (Figure 1).^4,8,11

A family history of melanoma, suggesting genetic susceptibility,is asignificant risk factor for melanoma.^1,3 Autosomal dominant familialmalignant melanoma syndromes are associated with mutations in the tumorsuppressor genes p15, p16, p21, or p27 on chromosome 9. Children with twoor more family members who have had primary malignant melanomas are particularlyat risk.^1,3 Some children with large dysplastic nevi withouta family history of melanomas may also show mutations in these tumor suppressorgenes.

Genetic or premature aging syndromes. Melanomas may develop in childhoodin individuals with one ofthe rare genetic syndromes, such as xerodermapigmentosum, in which a mutation in a DNA repair enzyme results in extremecutaneous photosensitivity to ultraviolet light. Premature aging syndromes,such as Cockayne, are also associated with increased risk.

Large congenitalpigmentednevi that involve more than 5% of the body surfacemay be a risk factor for developing nodular malignant melanoma within thecongenital nevus.^1,2 It is believed that the lifetime risk ofmelanoma with such nevi is 3% to 5%, though data are lacking. Small congenitalnevi carry a lifetime risk of less than 1%, with almost no risk before puberty.

Table 2 summarizes the known risk factors for melanoma. Unidentifiedfactors probably also play a role.

Benign or malignant?

The following guidelines can help distinguish melanoma from benign nevi:

Use the ABCD mnemonic--but know its limitations. The findings for thispopular mnemonic, outlined in Table 3, can be difficult to apply to children.Because many pigmented nevi in childhood are asymmetrical and most haveirregular borders, these criteria for suspecting melanoma may not be valid.Changes in color also must be evaluated carefully. The pigmented lesionthat goes from light brown to dark brown is not cause for worry, but theappearance of red, white, and blue areas in a pigmented lesion is. As forthe diameter of the lesion (the D in the mnemonic), anything larger than10 mm is significant. Almost all melanomas in adults are this size or bigger,whereas most benign pigmented nevi in prepubertal children are only 2 to6 mm. The ABCD mnemonic can be applied with fewer caveats to large pigmentednevi than to other moles, especially in adolescents.

Know what changes in a mole are normal. An understanding of the naturalhistory of pigmented nevi will help pediatricians evaluate a mole that is"darkening" or undergoing another kind of change. Most childrenfirst acquire pigmented nevi around 2or 3 years of age. The first nevi toappear are flat and small--from 2 to 4 mm. Microscopic examination revealssmall groups of extra melanocytes at the junction of the outer and middlelayers of skin--the so-called junctional nevi. About two in 10 of thesejunctional nevi will eventually develop larger groups of melanocytes inthe mid-dermis, elevating the previously flat lesion. These soft, raisedpapules are called compound nevi since they have extra melanocytes at boththe dermal-epidermal junction and in the mid-dermis.

Learn to recognize the benign moles. Five types of benign nevi may looklike a changing mole and thus be easily confused with melanoma (Table 4).

The fried-egg mole, a compound nevi, has a flat border and a raised,darker center (Figure 2). Many children have these nevi.

The halonevus is a pigmented mole surrounded by a halo of depigmentedskin (Figure 3). In time the mole will disappear. The disappearance of anevus is common and believed to be physiologic. About half the childrenwith halo nevi will have patches of vitiligo elsewhere. Some authoritiesbelieve that vitiligo represents an unregulated normal mechanism for eliminatingnevi.

The red mole, an uncommon nevus, is a soft papule that is red or red-brownrather than brown or black (Figure 4). These moles, called Spitz nevi, arecharacterized microscopically by unusual pigment cell shapes and extra bloodvessels.

The blue mole, also uncommon, is a firm, blue papule or nodule (Figure5). The microscope reveals many pigment cells deep in the dermis.

The nevus spilus is a mole that acquires spots (Figure 6). An uncommonnevus, it is a tan macule with many tiny (>0.1 mm) dark spots. The lesions,which often are present at birth, may acquire more dark spots as the childgrows.

Reject routine removal

To determine when to remove a mole, observe these do's and don'ts.

Don't remove moles routinely. The five benign moles described above donot have to be removed as a matter of course. Routine removal of nevi onacral areas, such as fingers, toes, palms, and soles, also is unnecessary,as is excision of nevi on genitalia or mucosal sites and of congenital nevismall enough to cover less than 5% of the skin surface.Larger moles shouldbe evaluated individually.

Nevi in prepubertal children generally don't merit removal unless thechild is subject to the risk factors for melanoma listed in Table 2. Acutechanges in the mole combined with abnormal ABCDs and familial melanoma area clear indication for removal. In our experience, however, even moles thatlook suspicious are microscopically bland in the prepubertal child.

Do consider removing "suspicious" moles in adolescents. Neviin adolescents that meet two or more criteria in the ABCD mnemonic (Figure7) should be excised to the subcutaneous tissues. Avoid shave excision,if possible. This method often leaves melanocytes in the site, which laterproliferate and repigment, possibly requiring a re-excision. Destructionof pigmented nevi by laser, freezing, or electrocautery is also ill advisedbecause these methods preclude a histologic analysis of the nevus.

Do get a second opinion on dysplastic nevi. Histologic criteriain adultsare not necessarily appropriate for children, whose growth can bring aboutchanges in the size and shape of melanocytes. Pathologists often use theterm "dysplasia" or "atypia" when melanocytes in a pigmentednevus differ in size and shape. When you get such a report, request a secondopinion from an experienced dermatopathologist. We don't have data to predictthe outcome from nevi considered dysplastic in childhood, though a childwith more than one first-degree family member who has had dysplastic nevimay be at greater risk of developing melanoma than other children.

Prevention strategies

In a child with no risk factors, routine mole checks before puberty areunnecessary. The advisability of yearly mole checks by a physician beginningat puberty increases with the number of risk factors. Examine the child'sentire skin surface; he or she should undress completely.

Exposure to ultraviolet rays is the one known external risk factor formelanoma that can be controlled, and sun protection does decrease melanomadevelopment in high-risk situations. Many people equate using sunscreenwith sun protection, however. This is unfortunate because intense sun exposureafter using sunscreen can offer more opportunity for ultraviolet injurythan a small amount of exposure without sunscreen.¹² In additionto sunscreen, good sun protection includes avoiding sunlight by planningoutdoor activities before 10 a.m. and after 4 p.m. and wearing protectiveclothing and headgear (see Table 5).¹³

Some observers worry that using sunscreen every day may cause vitaminD deficiency. Consuming milk and bread that contain added vitamin D circumventsthis problem, and there has been no increase in rickets in the US despitethe widespread use of sunscreens.

Reassuring parents

The pediatrician who determines that a prepubertal child has no riskfactors for melanoma can reassure her parents that the child's moles arebenign. Also offer some common-sense recommendations about sun protection,including the need to avoid midday sun and wear protective clothing in additionto using sunscreen. In children with risk factors for melanoma, start routinescreening of moles at puberty. This strategy combined with an understandingof which few moles merit follow-up puts the issue of moles and melanomainto perspective.

REFERENCES

1. Johnson TM, Dolan OM, Hamilton TA, et al: Clinical and histologictrends in melanoma. J Amer Acad Dermatol 1998;38:681

2. Porras BH Cockerell CJ: Cutaneous malignant melanoma: Classificationand clinical diagnosis. Seminars in Cutaneous Medicine and Surgery 1997;16:88

3.Finkel E: Sorting the hype from the facts in melanoma. Lancet 1998;351(9119):1866

4. Clark WH, From L, Bernardino EA, et al: The histogenesis and biologicbehavior of primary human malignant melanomas of the skin. Cancer Res 1969;29:705

5.Ruiz-Maldonado R, Orozco-Covarrubias ML: Malignant melanoma in children.Arch Dermatol 1997;133:363

6. Karlsson P, Boeryd B, Sander B, et al: Increasing incidence of cutaneousmalignant melanoma in children and adolescents 12­19 years of age inSweden 1973­92. Acta DermatoVenereol (Stockholm) 1998;78:289

7. Berg P, Lidelof B: Differences in malignant melanoma between childrenand adolescents. Arch Dermatol 1997;133:295

8. Langley RG, Sober AJ: A clinical review of the evidence for the roleof ultraviolet radiation in the etiology of cutaneous melanoma. Cancer Invest1997;15:561

9. Bataille V, Grulich A, Sasieni P, et al: The association between naeviand melanoma in populations with different levels of sun exposure: A jointcase-control study of melanoma in the UK and Australia. Brit J Cancer 1998;77:505

10. Swerdlow AJ, Weinstock MA: Do tanning lamps cause melanoma? An epidemiologicassessment. J Amer Acad Dermatol 1998;38:89

11. Breitbart M, Garbe C, Buttner P, et al: Ultraviolet light exposure,pigmentary traits and the development of melanocytic naevi and cutaenousmelanoma. A case control study of the German Central Malignant MelanomaRegistry. Acta Dermato Venereol 1997;77:374

12. Autier P, Dore J-F, Cattaruzza MS et al: Sunscreen use, wearing clothes,and number of nevi in 6- to 7-year-old European children. J Natl CancerInst 1998;90:1873

13. Kim HJ, Ghali FE, Tunnessen WW: Here comes the sun. ContemporaryPediatrics 1997;14(7):41

DR. MORELLI is Associate Professor of Dermatology and Pediatrics, Universityof Colorado School of Medicine, Denver.

DR. WESTON is Professor and Chairman, Department of Dermatology, atthe same institution.