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The worldwide incidence of cutaneous melanoma is increasing dramatically, at a rate of 3–9% per year during the past several decades. Although childhood melanoma is rare, with only 0.3% of newly diagnosed melanomas occurring in children < 14 years, and with melanoma accounting for only 1% of all pediatric malignancies, it still warrants familiarity on the part of the clinician. As in adults, the most successful treatment of melanoma in children remains prevention and early detection. For the purpose of this chapter, we define children as those younger than 14 years.
The risk of melanoma is increased in children with giant congenital melanocytic nevi, dysplastic nevi, xeroderma pigmentosum (XP), and immunosuppression. Approximately 20% of patients with xeroderma pigmentosum develop melanoma, though not necessarily in childhood.
Both genetic immunodeficiency states and secondary immunosuppression because of organ transplantation or HIV infection confer modest additional risk of developing cutaneous melanoma, although these malignancies more frequently arise during adulthood. In adults, the risk factors for melanoma have been identified as the following: fair skin, light hair, increased number of melanocytic nevi, inability to tan, blistering sunburns in childhood, or personal or family history of melanoma. The relevance of these risk factors in children is unclear, although Novakovic et al.
has reported melanomas in children as young as age 3 in familial melanoma kindreds.
Congenital malignant melanoma
Melanoma may develop in utero in one of three ways: (1) transplacental transmission from a mother with metastatic melanoma to her fetus, (2) primary melanoma arising within a giant congenital melanocytic nevus (GCMN), or, (3) very rarely, as a primary de novo cutaneous congenital melanoma.
Transplacental transmission of melanoma was first reported in 1949,
Clinically, neonates with transplacentally acquired melanoma present with multiple small, black macules, papules, or nodules or subcutaneous masses. Multiorgan involvement is common. Although the prognosis is very poor, with fatal outcomes by a few months of age, spontaneous complete regression has been reported.
Primary congenital melanoma may very rarely arise within a GCMN. It tends to develop deep in the dermis or in the subcutaneous fat and is difficult to detect clinically, secondary to the irregular surface and complexity of the lesions. Recently, one of us (M. C. Mihm, Jr., et al., unpublished observations, 2000) has reported a pigment-synthesizing melanoma present at birth in a congenital nevus of the scalp of an African-American neonate. GCMNs will be discussed in more detail in the next section.
Finally, congenital melanoma may arise de novo in utero without preexisting maternal melanoma. On presentation, these tend to be between 1 and 3 cm in diameter, grow rapidly, ulcerate, and bleed.
It must be emphasized that congenital melanoma is very rare and is often difficult to distinguish from atypical spindle-cell nevi. We strongly urge that consultation be obtained for these very problematic lesions.
Primary melanoma arising within a GCMN
The incidence of GCMN is approximately 1 in 20,000 newborns.
GCMNs are commonly defined as larger than 20 cm at the largest diameter, although definitions may vary; some prefer defining GCMNs as those congenital nevi that would require a graft for closure after surgical removal (Fig 1). They are more frequently seen in girls, and they occur most frequently on the trunk (Fig 2), although they may occur on the extremities or the head. Smaller satellite lesions are often present on the skin or mucous membranes. When located on the extremities, GCMNs have been associated with limb underdevelopment.
The concern with GCMNs is that at least one third of prepubertal melanomas arise within them. As mentioned earlier, these melanomas are often difficult to detect because of the underlying complex morphology of the GCMN. Often the melanoma arises from the deep portions of the nevus (Figure 3, Figure 4, Figure 5), within the reticular dermis and/or subcutaneous fat, with no visible changes in the epidermal component of the nevus. These deep lesions are usually clinically diagnosed as epidermal cysts. Therefore, the development of any cystlike structure in a GCMN should be biopsied. Furthermore, nests of nevus cells may at times extend into soft tissue such as muscle. When lesions are present on the scalp, especially in the occipital area, the nevus cells may extend into the meninges, into the substance of the brain, including the ventricles and the choroid plexus. A gradual proliferation of these cells can occur with resultant hydrocephalus (Touraine’s syndrome).
In one case, melanoma developed in a pectoral muscle nest of nevus cells after removal of a truncal GCMN. The lesion had been completely excised with skin grafting, and the melanoma developed under the graft.
This risk is very high in early childhood; half of the melanomas develop in the first decade of life, particularly in the first 5 years. This early peak is associated with a second peak of incidence in adult life. Thus, there is a bimodal distribution to the pattern of melanoma development in the GCMN. Proliferative nodules occur in GCMNs, especially in the neonatal period. These nodules can be very difficult to differentiate both clinically and histologically from melanoma. An experienced dermatopathologist should always be consulted when such a nodule is atypical and melanoma is considered in the differential diagnosis.
Management of patients with GCMNs is complex. Some advocate excision of the entire lesion during early childhood because of the risk of malignancy. This is usually accomplished with staged surgical resection using tissue expanders. Unfortunately, at times complete excision is not feasible because of the large size of the lesion, its location, or the presence of satellite lesions or even deep placement of nevus cells below the skin. Excision must extend down to the muscle fascia and even include part of the muscle if the nevus nests are seen. Laser treatment of GCMNs is not an appropriate therapy to reduce the risk of melanoma because the tissue ablation does not extend deeply enough into the dermis to effectively obliterate the deeper melanocytes that are part of the lesion. If surgical resection is not feasible, close follow-up is recommended at least once a year. Photographs may be helpful in monitoring a lesion for change. Some groups think that complete removal of GCMN for melanoma prophylaxis is too mutilating to consider as standard therapy. The policy of our Pigmented Lesion Clinic is to consider each case separately and decide on the course to be taken in discussion with the patient and/or the family.
Primary melanoma arising within small congenital melanocytic nevi
Small melanocytic congenital nevi (SCMNs) are found in 1% of newborns (Figure 6, Figure 7). No consensus has been reached on whether these lesions confer an increased risk of developing malignant melanoma. If malignant melanoma does arise within an SCMN (Fig 8), it tends to be in a postpubescent child, unlike a CGMN, wherein the risk of malignant melanoma is quite significant in early childhood. These lesions should be managed on a case-by-case basis (Fig 9). When considered appropriate, prophylactic removal of these lesions is usually done in late childhood or early adolescence, when they can be removed under local anesthesia. For example, lesions in areas such as the lower back, buttocks, or the back of the legs that are difficult for the patient to follow are usually removed. Otherwise, the child can be followed up clinically with photographs at least once a year. Photographs of the lesion may be helpful in monitoring for change.
Primary melanoma arising in association with dysplastic nevi
Dysplastic nevi can be precursors of melanoma, and familial cases of dysplastic nevi may occur. The first indication that a child will develop dysplastic nevi is the appearance of a large number of normal-appearing nevi (greater than 20) by age 5 or 6. Many of these lesions, mainly small and uniformly colored, evolve into typical dysplastic nevi as the children mature. The dysplastic nevi tend to be larger than common, acquired nevi, measuring 5–15 mm, and in children often occur first on the scalp.
They often have “fuzzy” borders and are variable in color, with shades of brown, tan, and pink. Cutaneous melanoma is more common in patients with familial melanomas and dysplastic nevi; familial melanomas tend to occur at an earlier age, even during the teenage years and early adulthood.
Follow-up of children with dysplastic nevi should focus on preventive measures such as sun avoidance and sunblock use, along with annual skin checks by a dermatologist, and periodic photographs of clinically atypical lesions. Again, because a large number of normal-appearing nevi at ages 5–6 years are often a marker for future development of dysplastic nevi, the child with many nevi should be screened starting no later than age 8–10 years. Prophylactic removal of all dysplastic nevi is not advised.
De novo melanoma
Melanomas that do not arise from any preexisting pigmented lesion account for 40–50% of childhood melanomas.
The clinical features may include the following: a new pigmented lesion that grows rapidly, bleeds, or changes color (Fig 10). More advanced melanomas may present with a subcutaneous mass or enlargement of regional lymph nodes (Fig 11 A, B). As in adults, the most common subtype of melanoma is superficial spreading.
The criteria for diagnosis of malignant melanoma in children are identical to those in adults: any suspicious lesion is biopsied, preferably by excisional biopsy, and examined histologically. Excisional biopsy allows the pathologist to look at the entire lesion. In children, however, there are a few diagnostic confounders that are usually less of a problem in adults: the Spitz nevus and the dermal nodules of the GCMNs. Spitz nevi are more common in children than in adults, clinically appearing as < 1-cm, dome-shaped, pink-tan papules, preferentially involving the head and neck. Microscopically, Spitz nevi and melanoma share many features, although clinically, the Spitz nevus is a benign lesion and in most cases, especially in the hands of an experienced dermatopathologist, can be successfully diagnosed. Some lesions defy exact classification, and often unusual clinical features are clues to their nature and behavior, such as large lesions > 1.0 cm, lesions with an irregular shape, and large lesions that ulcerate. In the case of any doubtful lesion, we recommend excision with as close to a 1.0-cm margin as possible, considering location and cosmesis. Some reasonable guidelines have been established to evaluate these unusual or “borderline” lesions.
Once the diagnosis of malignant melanoma has been established, surgical excision should be performed, with 1-cm margins for melanomas < 1 mm in depth and 2-cm margins for thicker melanomas. Dissection of regional lymph nodes in the past has usually been reserved only for clinically apparent lymphadenopathy. Regarding the relatively recent introduction of sentinel nodal biopsy, the same parameters as in adults will probably be used as indications for recommending its use in children. As of this time, however, the sentinel node biopsy is an experimental technique. It serves as one of the easiest, less costly, and efficient methods for staging. Patients with negative sentinel nodes are spared the cost and morbidity of an elective node dissection.
Clinical trials of melanoma therapies for disseminated disease do not usually include children, and there are few pediatric data on stage III and IV melanoma. In a single institutional trial, four children with advanced melanoma responded well to the chemotherapeutic agent dacarbazine.
Other experimental therapies, including interleukin-2, interferon alfa-2b, and vaccine therapies, though sporadically used, have not been studied in children in any randomized, protocol-driven fashion.
Ultimately, as in adults, there is no effective therapy for metastatic melanoma in children. Therefore, the main focus of the parent, the pediatrician, and the dermatologist should be risk reduction and early detection of melanoma. The former consists primarily of avoiding intense sunlight exposure, using protective clothing and broad-spectrum sunblock, and educating children. In Australia, where the incidence of melanoma is very high, a public education campaign about sun protection begins in preschool, with the thought that behaviors learned by children tend to persist throughout adult life. Early detection requires a high index of clinical suspicion, especially on the part of the pediatrician, who sees children with much more regularity than a dermatologist, of any rapidly growing or otherwise atypical pigmented lesion. In addition, the physician should recognize the elevated risk of any child with a family history of melanoma, GCMN, or dysplastic nevi. Again, prevention and early clinical diagnosis are the only current effective cure for cutaneous melanoma. For additional studies on childhood melanoma, see References