Melanomas in prepubescent children: review comprehensively, critique historically, criteria diagnostically, and course biologically

Melanoma in children: A systematic review and individual patient meta-analysis

The current evidence on paediatric melanoma is heterogeneous, especially regarding the prognosis of different histological subtypes. We sought to systematically review the evidence on paediatric melanoma, highlighting the major sources of heterogeneity and focusing on available data on single patients. A systematic search was performed from 1948 to 25 January 2021. Only studies reporting at least one case of cutaneous melanoma in patients aged ≤18 years were included. Unknown primary and uncertain malignant melanomas were excluded. Three couples of authors independently performed title/abstract screening and two different authors reviewed all the relevant full texts. The selected articles were manually cross-checked for overlapping data for qualitative synthesis. Subsequently data on single patients were extracted to perform a patient-level meta-analysis. PROSPERO registration number: CRD42021233248. The main outcomes were melanoma-specific survival (MSS) and progression-free survival (PFS) outcomes. Separate analyses were done of cases with complete information on histologic subtype, focusing on superficial spreading (SSM), nodular (NM) and spitzoid melanomas, as well as of those classified as de-novo (DNM) and acquired or congenital nevus-associated melanomas (NAM). The qualitative synthesis covered 266 studies; however, data on single patients were available from 213 studies including 1002 patients. Among histologic subtypes, NM had a lower MSS than both SSM and spitzoid melanoma, and a lower PFS than SSM. Spitzoid melanoma had a significantly higher progression risk than SSM and trended toward lower mortality. Focusing on nevus-associated status, DNM demonstrated better MSS after progression than congenital NAM, and no differences were highlighted in PFS. Our findings describe the existence of different biological patterns in paediatric melanoma. Specifically, spitzoid melanomas demonstrated intermediate behaviour between SSM and NM and showed a high risk of nodal progression but low mortality. This raises the question of whether spitzoid lesions are being over-diagnosed as melanoma in childhood.

Conceptual Evolution and Current Approach to Spitz Tumors

Over the past several decades, the study of Spitz neoplasms has flourished, with expanded conceptualization and refined terminology, providing a framework for the assessment and classification of Spitz nevi, atypical Spitz Tumors, and Spitz melanoma. Cancer genomics have generated concepts such as driver and passenger genes and clonal evolution, which can be applied to Spitz tumors. Herein, we provide a historical perspective, followed by a summary of current knowledge and clinical approaches for these challenging tumors.

Cutaneous melanoma in children and adolescents: The EXPeRT/PARTNER diagnostic and therapeutic recommendations

Cutaneous melanoma is rare in children and, like other very rare pediatric tumors, it suffers from a shortage of knowledge and clinical expertise. The clinical management of pediatric melanoma is often challenging. Its clinical and pathological diagnosis may be difficult, and there is no standard treatment. In the absence of specific treatment guidelines, young patients are generally treated following the same principle as for adults, but concern remains about their access to clinical trials and new drugs, which have been shown to dramatically change the natural history of advanced melanoma. This paper presents the internationally recognized recommendations for the diagnosis and treatment of children and adolescents with cutaneous melanoma, established by the European Cooperative Study Group for Pediatric Rare Tumors (EXPeRT) within the EU-funded project called PARTNER (Paediatric Rare Tumours Network - European Registry). Main recommendations for melanoma are to discuss pediatric patients in multidisciplinary teams that include both pediatric oncologists and specialists in adult melanoma; to enroll patients in prospective trials, if available; to collect data in national-international databases; and to develop an effective international collaboration between pediatric and adult melanoma groups in order to facilitate the transfer of potentially effective new agents from the adult to the pediatric setting.

A Clinicoepidemiological Study of Melanoma in Young Patients (20 Years of Age or Less) in Alberta, Canada, From 1992 to 2011

The epidemiological trends of malignant melanoma have been well described in the literature. However, there remains a paucity of population-based studies assessing melanoma epidemiology in our younger patients (20 years of age or less). Other studies indicate that melanoma incidence has risen in pediatric populations over the last several decades and that these tumors may display different clinical characteristics from those arising in adult populations. We conducted a retrospective, population-based analysis of all incident cases of melanoma occurring in young patients aged ≤20 years in Alberta from 1992 to 2011. Information, including patient age, sex, anatomical location, date of diagnosis, histological subtype (if available), level of invasion, and date of death (if applicable), was obtained from the Alberta Cancer Registry. All cases occurring during a 10-year period from 1993 to 2011 have been reviewed. A total of 71 cases were diagnosed during this time (63% female and 37% male). Age range was 0-20 years (mean of 17.5 years). Truncal melanomas made up 36% of cases, while 28% occurred on the lower limbs, 17% on the upper limbs, and 18% in the head and neck region. Average Breslow thickness was 1.97 mm; 67% of tumors were less than 1 mm thick. Unfortunately, 8 of 71 patients died from their disease. Overall, the incidence of melanoma in patients aged ≤20 years appeared to decrease in Alberta in the past 20 years; however, there has been an increase in the thickness of melanoma at diagnosis, which needs to be addressed.

Cutaneous melanoma in adolescents and young adults

Cutaneous melanoma is rare in children, but has greater incidence in adolescents and young adults (AYAs). Diagnosis may be challenging due to its rarity in these age groups. Few studies have specifically addressed the topic of AYA melanoma. Though young-age melanoma may have particular biological characteristics, available data suggest that its clinical history is similar to that of adults. However, advances in treatment of adult melanoma have not been reflected in the treatment of AYAs. There is no standard treatment, and access to clinical trials is difficult for AYAs. Further efforts are needed to overcome these issues by improving cooperation with experts on adult melanoma.

Pediatric patients with cutaneous melanoma: A European study

INTRODUCTION

Cutaneous melanoma is rare in childhood and published studies have mainly been retrospective single-institution series or small case series. Given the absence of clinical protocols dedicated to pediatric melanoma, the treatment approach is generally extrapolated from the ones applied to adults.

METHODS

Coordinated by the European Cooperative Study Group for Pediatric Rare Tumors (EXPeRT), this study collected patients prospectively registered between 2002 and 2012 under national cooperative projects dedicated to rare pediatric tumors in Italy, Poland, Germany, and France. Additional cases were collected from dermatology registries in Germany and Israel.

RESULTS

A total of 219 patients aged 0-18 years (median 14.4) were included in the analysis. Sentinel lymph node biopsy was performed in 112 patients (76% of those with Breslow thickness > 0.75 mm) and was positive in 37.5%. Systemic therapy was used in 33 cases. In stage III cases, survival rates were similar for patients who received (23 cases) or not (21 cases) adjuvant therapy. For the whole series, 3-year overall and disease-free survival rates were 91.4% and 84.0%, respectively (median follow-up 41.8 months). Tumor site, tumor stage, and ulceration influenced survival rates. Patients treated by pediatric oncologists (n = 140) were more likely to have advanced disease than those treated by dermatologists (n = 79).

DISCUSSION

This study would suggest that the clinical history of melanoma in children and adolescents might resemble that of adult counterpart. Cooperative efforts are needed to make new drugs more readily available to pediatric patients to increase the outcome of patient with advanced disease.

Paediatric melanoma

Paediatric melanoma, although rare, is the most common skin cancer in children. Our current knowledge on paediatric melanoma incidence trends is expanding, as several studies have addressed this issue with conflicting results. Known risk factors for paediatric melanoma include family history of melanoma, a previous history of malignancy, large congenital nevi, numerous melanocytic nevi, sunburns, increased UV exposure and a sun-sensitive phenotype. In younger children, melanoma more often presents with atypical features, such as a changing, amelanotic or uniformly coloured, often bleeding lesion, not fulfilling in most cases the conventional ABCDE criteria. The major differential diagnoses are melanocytic nevi, proliferative nodules in congenital nevi and atypical Spitz tumours. Moreover, in the younger age group non-Caucasian children are over-represented, tumours tend to be thicker and lymph nodes are often involved. Despite the frequent diagnosis at an advanced stage, the overall survival is fair in paediatric melanoma. Specific guidelines for management of melanoma in children do not exist, and most often the disease is treated similarly to melanoma in adults.

Pediatric Melanoma: A 35-year Population-based Review

Background:

Melanoma is a rare neoplasm in the pediatric population. Recent publications suggest a possible increase in incidence over the past few decades. The purpose of this study was to analyze trends in pediatric patients diagnosed with malignant melanoma in British Columbia (BC) in the past 35 years.

Methods:

A retrospective review was performed. All patients in BC diagnosed with melanoma before 18 years of age from 1979 to 2014 were included. Patient demographics, melanoma description, treatment details, and survival data were collected.

Results:

Seventy-eight subjects were identified for the study. Patients were equally distributed by sex. Sixty-one (78%) of the subjects were diagnosed in the postpubertal age (≥12 years old). The most common sites of occurrence were the extremities (n = 33) and the trunk (n = 27), with the location on the trunk showing the highest mortality rate (22%). All patients were surgically treated and some had additional chemotherapy (12) and/or radiotherapy (12). Fatal outcome was recorded in 12 of the 78 subjects, 10 of whom had postpubertal diagnosis. The average time from date of diagnosis to date of death was 9.3 years.

Conclusions:

The incidence of melanoma in the pediatric population remains exceedingly rare: less than 2.5 per million children younger than 18 years. The diagnosis is rarely made before puberty; the incidence is equal in males and females and has not changed over a 35-year time period in BC. Our study shows 85% survival with the majority of patients having had surgical excision only.

Pediatric melanomas often mimic benign skin lesions: A retrospective study

BACKGROUND

Childhood melanoma can be misdiagnosed because of its rarity and atypical presentation.

OBJECTIVE

We sought to correlate the clinical appearance of pediatric melanomas with Breslow depth and clinical behavior, and to identify diagnostic errors made by dermatologists and nondermatologist physicians.

METHODS

This was a retrospective review of Mayo Clinic records of children and young adults 21 years of age or younger with a diagnosis of primary cutaneous melanoma between January 2000 and January 2015.

RESULTS

Pediatric melanomas that mimicked benign skin lesions were more often deeper (>1 mm; odds ratio 5.48; P = .002) and had a higher T stage (odds ratio [T2, T3, or T4] 6.28; P = .001) than melanomas with a clinically malignant appearance. Of pediatric melanomas, 66% originally diagnosed as benign melanocytic lesions exhibited changes in size, shape, and color.

LIMITATIONS

Sample size and retrospective design are limitations.

CONCLUSIONS

Benign-appearing pediatric skin lesions with a history of evolution, bleeding, or ulceration should raise suspicion for melanoma. Melanomas demonstrating these features are associated with a higher Breslow depth and T stage. Although biopsy of all lesions that exhibit change in children is not practical, safe, or desired, close monitoring is recommended.

Dermpath quiz: An irregularly colored papule on the back of an adolescent female

This learning exercise challenges clinicians and dermatopathologists to consider the differential diagnosis of an unevenly colored solitary papule over the upper back of an adolescent female.

Paediatric melanoma

Cutaneous melanoma occurs only rarely in children under 10 years of age. Mimics of melanoma, including Spitz naevi and proliferative nodules in congenital melanocytic naevi are much more frequent in this age group. Melanoma arising in congenital melanocytic naevus is uncommon, but can show aggressive behaviour. Although spitzoid lesions constitute the majority of 'diagnostically challenging' cases, they are an uncommon cause of mortality in this age group. Among lesions with undoubted metastatic potential, there are biologically distinct tumours which differ significantly in behaviour from the common types of melanoma seen in adults. In patients over 10 years of age and increasingly into the late adolescent years, melanoma is a relatively common neoplasm. Just as in adult patients, care should be taken to exclude melanoma mimics. Particular care is warranted in this older age group in the assessment of lesions with spitzoid morphology as there is significant potential for both over-and under-diagnosis.

Early detection of melanoma: reviewing the ABCDEs

Over the course of their nearly 30-year history, the ABCD(E) criteria have been used globally in medical education and in the lay press to provide simple parameters for assessment of pigmented lesions that need to be further evaluated by a dermatologist. In this article, the efficacy and limitations of the ABCDE criteria as both a clinical tool and a public message will be reviewed.

Case reports of fatal or metastasizing melanoma in children and adolescents: a systematic analysis of the literature

Childhood melanoma (ChM) is rare, with clinical and epidemiologic characteristics that differ from those of adult melanomas. The objective of the current study was to systematically identify and analyze case reports and case series of fatal and metastasizing ChM in the medical literature. ChM case reports with a fatal outcome or metastases were identified using a Medline search and subdivided into ChM developing in the absence of a congenital melanocytic nevus (ChM without CMN) and ChM associated with a CMN (ChM with CMN); 258 cases of ChM without CMN (206 cutaneous, 52 noncutaneous) were identified. In cutaneous ChM without CMN with a fatal outcome (n = 155), the mean age at diagnosis was 13.1 years (median 14 yrs). The mean Breslow index in this group was 8.5 mm for children ages 0 to 10 years and 3.7 mm for children ages 11 to 18 years. In ChM with CMN (n = 178; 112 cutaneous, 66 central nervous system [CNS]), the mean age at diagnosis was 5.8 years for cutaneous melanoma (median 3 yrs) and 5.5 years for CMN-associated CNS melanoma (median 3 yrs). The majority of CMN-associated cutaneous melanomas developed in small and giant CMN (vs medium and large); 53.9% of CNS melanomas developed in patients with multiple medium CMN. This study represents the largest and most complete synopsis of ChM case reports in the medical literature. Our analysis supports the view that cutaneous ChM without CMN (or associated with smaller CMN) differs in several important aspects from ChM associated with large or giant CMN.

"Lentiginous melanoma": full-fledged melanoma or melanoma precursor?

On the basis of a critical review of published literature, it is concluded that there is as yet insufficient evidence to conclude that the melanocytic lesion, which is currently known as "lentiginous melanoma," is a full-fledged melanoma, with the capacity to metastasize to distant sites and to cause the demise of the patient. It is proposed that this lesion is better designated as "lentiginous SAMPUS," that is, a superficial atypical melanocytic proliferation of uncertain significance, with a lentiginous, or predominantly lentiginous, arrangement of the junctional component. As there is uncertainty regarding its actual metastatic potential or the likelihood of progression to melanoma NOS, the lesion should be removed completely, with free surgical margins.

Cutaneous melanoma in children and adolescents: the Italian rare tumors in pediatric age project experience

OBJECTIVE

To describe a series of cutaneous melanoma in children collected by the Italian Rare Tumors in Pediatric Age project.

STUDY DESIGN

From 2000 to 2012, 54 patients younger than 18 years of age were prospectively registered and treated at 12 Italian pediatric centers on the basis of the same diagnostic/therapeutic recommendations and with the same forms to record clinical data.

RESULTS

Considering the estimated annual incidence in Italy, the registered cases accounted for 30% of those expected in children and 10% of adolescents. Clinically, 47% of the tumors were amelanotic and 81% were raised, 39% of cases had tumor thickness >2 mm, and 36% had lymph node involvement. For the whole series, 5-year event-free survival and overall survival rates were 75.2% and 84.6%, respectively. Patient survival correlated with tumor stage and ulceration. No relapses were recorded for T1-2 (thickness <2 mm), N0, and stage 0-I-II cases.

CONCLUSION

We suggest that the variables influencing survival in children with melanoma are the same as for adults, the clinical approach used in adults is feasible in children, and pediatric cases are more likely to have advanced disease at diagnosis but similar survival. New effective drugs are needed for advanced disease, and biological studies and international cooperative schemes are warranted.

Pediatric melanoma: analysis of an international registry

BACKGROUND

The management of pediatric melanoma (PM) has largely been extrapolated from adult data. However, the behavior of PM appears to differ from its adult counterparts. Therefore, an international PM registry was created and analyzed.

METHODS

Twelve institutions contributed deidentified clinicopathologic and outcome data for patients diagnosed with PM from 1953 through 2008.

RESULTS

Overall survival (OS) data were reported for 365 patients with invasive PM who had adequate follow-up data. The mean age of the patients was 16 years (range 1 year-21 years). The 10-year OS rate, 80.6%, tended to vary by patient age: 100% for those aged birth to 10 years, 69.7% for those aged > 10 years to 15 years, and 79.5% for those aged > 15 years to 20 years (P = .147). Patients with melanomas measuring ≤ 1 mm had a favorable prognosis (10-year OS rate of 97%), whereas survival was lower but similar for patients with melanomas measuring > 1 mm to 2 mm, > 2 mm to 4 mm, and > 4 mm (70%, 78%, and 80%, respectively; P = .0077). Ulceration and lymph node metastasis were found to be correlated with worse survival (P = .022 and P = .017, respectively). The 10-year OS rate was 94.1% for patients with American Joint Committee on Cancer stage I disease, 79.6% for those with stage II disease, and 77.1% for patients with stage III disease (P < .001).

CONCLUSIONS

Tumor thickness, ulceration, lymph node status, and stage were found to be significant predictors of survival in patients with PM, similar to adult melanoma. There is a trend toward increased survival in children aged ≤ 10 years versus adolescents aged > 10 years. Further analyses are needed to probe for potential biological and behavioral differences in pediatric versus adult melanoma.

Incidence of childhood and adolescent melanoma in the United States: 1973-2009

OBJECTIVE

Childhood and adolescent melanoma is rare but has been increasing. To gain insight into possible reasons underlying this observation, we analyzed trends in melanoma incidence diagnosed between the ages of 0 and 19 years among US whites by gender, stage, age at diagnosis, and primary site. We also investigated incidence trends by UV-B exposure levels.

METHODS

By using Surveillance, Epidemiology, and End Results (SEER) program data (1973-2009), we calculated age-adjusted incidence rates (IRs), annual percent changes, and 95% confidence intervals for each category of interest. Incidence trends were also evaluated by using joinpoint and local regression models. SEER registries were categorized with respect to low or high UV-B radiation exposure.

RESULTS

From 1973 through 2009, 1230 children of white race were diagnosed with malignant melanoma. Overall, pediatric melanoma increased by an average of 2% per year (95% confidence interval, 1.4%-2.7%). Girls, 15- to 19-year-olds, and individuals with low UV-B exposure had significantly higher IRs than boys, younger children, and those living in SEER registries categorized as high UV-B. Over the study period, boys experienced increased IRs for melanoma on the face and trunk, and females on the lower limbs and hip. The only decreased incidence trend we observed was among 15- to 19-year-olds in the high UV-B exposure group from 1985 through 2009. Local regression curves indicated similar patterns.

CONCLUSIONS

These results may help elucidate possible risk factors for adolescent melanoma, but additional individual-level studies will be necessary to determine the reasons for increasing incidence trends.

Imaging mass spectrometry--a new and promising method to differentiate Spitz nevi from Spitzoid malignant melanomas

BACKGROUND

Differentiating Spitz nevus (SN) from Spitzoid malignant melanoma (SMM) is one the most difficult problems in dermatopathology.

SPECIFIC AIM

To identify differences on proteomic level between SN and SMM.

METHODS

We performed Imaging Mass Spectrometry analysis on formalin-fixed, paraffin-embedded tissue samples to identify differences on proteomic level between SN and SMM. The diagnosis of SN and SMM was based on histopathologic criteria, clinical features, and follow-up data, which confirmed that none of the lesions diagnosed as SN recurred or metastasized. The melanocytic component (tumor) and tumor microenvironment (dermis) from 114 cases of SN and SMM from the Yale Spitzoid Neoplasm Repository were analyzed. After obtaining mass spectra from each sample, classification models were built using a training set of biopsies from 26 SN and 25 SMM separately for tumor and for dermis. The classification algorithms developed on the training data set were validated on another set of 30 samples from SN and 33 from SMM.

RESULTS

We found proteomic differences between the melanocytic components of SN and SMM and identified 5 peptides that were differentially expressed in the 2 groups. From these data, 29 of 30 SN and 26 of 29 SMM were recognized correctly based on tumor analysis in the validation set. This method correctly classified SN with 97% sensitivity and 90% specificity in the validation cohort.

CONCLUSIONS

Imaging Mass Spectrometry analysis can reliably differentiate SN from SMM in formalin-fixed, paraffin-embedded tissue based on proteomic differences.

The 'epidemic' of melanoma between under- and overdiagnosis

In the past decades, the incidence of melanoma has been reported to rise in epidemic proportions. The chief reason for that pseudo-epidemic is improved criteria for diagnosis that allow melanomas to be recognized far more accurately and at earlier stages. The rising number of melanomas diagnosed has resulted in increased diagnostic scrutiny, more pigmented lesions being biopsied and more melanomas recognized, thus enhancing the 'epidemic' in self-perpetuating fashion. Regression of melanomas may, in part, explain why lesions undetected before did not result in a far higher mortality. Another potential reason for the disparity between increasing incidence of melanoma and relatively steady mortality may be overdiagnosis of melanoma. The latter may be curtailed by establishment of well-defined diagnostic categories, efforts to establish reliable criteria for recognition of those categories, better clinicopathologic correlation, postponement of biopsy of pigmented lesions in the case of irritation and excisional rather than incisional biopsies.

In situ melanoma of the nail unit in children: report of two cases in fair-skinned Caucasian children

Nail melanoma in children is rarely reported in the literature, and all of the published cases were diagnosed in dark-skinned phototypes or in Asians. We report two cases of in situ nail matrix melanoma presenting as longitudinal melanonychia (LM) in fair-skinned children of Italian origin. Nail plate dermatoscopy revealed a brown background with lines of irregular color, spacing, and thickness in both cases. Histopathology of the excised lesions showed melanoma in situ. Clinical, dermatoscopic, and pathological criteria that permit clear differentiation of benign melanocytic activation or proliferation from nail matrix melanoma are not established for children. The presence of a pigmented band of a single nail in a child usually represents a problem for clinicians, because the clinical and dermatoscopic features that are considered possible indicators of nail unit melanoma in adults are frequently observed in benign melanocytic hyperplasia and nevi in children. There is therefore the need to find parameters useful for clinical and dermatoscopic diagnosis in childhood nail pigmentation and to reach a consensus on management of children with a band of LM.

Spitz nevi and other Spitzoid lesions part I. Background and diagnoses

Spitz nevi are melanocytic proliferations that are characterized by spindled and/or epithelioid nevomelanocytes. First interpreted as juvenile melanoma, these lesions were later characterized as benign and were observed to affect all age groups. Today, contrasting opinions persist regarding the fundamental benignancy versus malignancy within the spectrum of Spitz tumors. Beyond clinical outcome, this controversy has also been fueled by complex and sometimes convoluted classification schemes based on pathologic characteristics. More recently, immunophenotypic and molecular analyses have begun to clarify the etiologic nature of these tumors. Recent evidence suggests that histopathologic features that suggest more aggressiveness in Spitz tumors relate to mitoses and inflammation.

Melanoma in children

CONTEXT

Cutaneous melanoma in childhood (CMC) is rare; therefore, its prognostic factors and biologic behavior, and the effectiveness of adjuvant techniques for CMC remain mostly unknown.

OBJECTIVE

To review the most useful, evidence-based practice criteria for establishing the diagnosis of CMC, for which universally accepted criteria are lacking, in order to facilitate the interpretation and comparison of the results from different institutions, and to perform systematic reviews and meta-analysis.

DATA SOURCES

A comprehensive review of the most relevant previous single-institution series reported in the literature since 1990, including our cumulative experience of 137 cases of primary cutaneous and mucosal melanoma in patients younger than 18 years. Special characteristics of melanoma in children are discussed, regarding clinical settings and risk factors, helpful histologic features, and immunohistochemical patterns for diagnosis and prognosis.

CONCLUSIONS

Careful analysis of histologic features as well as the additional information provided by immunohistochemistry should allow for a correct diagnosis in most cases of melanoma in children. Although it seems that pediatric patients with melanoma have higher survival probability than adults, still a number of children will develop metastasis and die of their disease, particularly when melanoma is diagnosed after puberty. Until further studies more accurately determine the prognosis, a prudent approach to CMC diagnosis and therapy seems to follow the same principles as those established for adult melanoma.

BRAF, NRAS and HRAS mutations in spitzoid tumours and their possible pathogenetic significance

BACKGROUND

The relationships between so-called spitzoid tumours have proven difficult to understand.

OBJECTIVES

To address three questions: does spitzoid tumour morphological similarity reflect molecular similarity? Does Spitz naevus progress into spitzoid melanoma? Are ambiguous spitzoid tumours genuine entities?

METHODS

BRAF, NRAS and HRAS mutations were analysed using single-strand conformational polymorphism analysis and sequencing.

RESULTS

Both Spitz naevi and spitzoid melanoma had a lower combined BRAF and NRAS mutation frequency compared with common acquired naevi (P = 0.0001) and common forms of melanoma (P = 0.0072), respectively. To look for evidence of progression from Spitz naevi to spitzoid melanoma, HRAS was analysed in 21 spitzoid melanomas, with no mutations identified. The binomial probability of this was 0.03 based on an assumption of a 15% mutation frequency in Spitz naevi with unbiased progression. Under these assumptions, HRAS mutations must be rare/absent in spitzoid melanoma. Thus, Spitz naevi seem unlikely to progress into spitzoid melanoma, implying that ambiguous spitzoid tumours cannot be intermediate degrees of progression. In addition, the data suggest that HRAS mutation is a potential marker of benign behaviour, in support of which none of three HRAS mutant spitzoid cases metastasized.

CONCLUSIONS

First, the morphological similarity of spitzoid tumours reflects an underlying molecular similarity, namely a relative lack of dependence on BRAF/NRAS mutations. Second, Spitz naevi do not appear to progress into spitzoid melanoma, and consequently ambiguous spitzoid tumours are likely to be unclassifiable Spitz naevi or spitzoid melanoma rather than genuine entities. Third, HRAS mutation may be a marker of Spitz naevus, raising the possibility that other molecular markers for discriminating Spitz naevi from spitzoid melanoma can be discovered.

Study of Nevi in Children (SONIC): baseline findings and predictors of nevus count

The authors report baseline findings and predictors of nevus count (log total nevi) at the completion of year 1 (2004) of the first known population-based, prospective study of nevi in a US cohort of children. Overall, 64% (n = 443/691) of grade 5 students and their parents in Framingham, Massachusetts, completed surveys and underwent digital photography. Total nevus count was associated with skin and hair color and tendency to burn, as measured by a sun sensitivity index. In multivariate analyses, male gender (rate ratio (RR) = 1.38, 95% confidence interval (CI): 1.22, 1.55; P < 0.0001), spending 5-6 weekly hours outdoors between 10 AM and 4 PM (RR = 1.13, 95% CI: 1.00, 1.28; P = 0.051), getting a painful sunburn once (RR = 1.24, 95% CI: 0.98, 1.57; P = 0.073) and at least twice (RR = 1.34, 95% CI: 0.99, 1.82; P = 0.061), and wearing a shirt at the beach or pool rarely (RR = 1.29, 95% CI: 1.08, 1.54; P = 0.005), sometimes (RR = 1.26, 95% CI: 1.01, 1.57; P = 0.041), and often and always (RR = 1.32, 95% CI: 1.13, 1.54; P = 0.001) were associated with increased number of nevi. Identifying factors that predict the development of nevi will improve primary prevention efforts during early life.

Understanding spitzoid tumours: new insights from molecular pathology

Spitzoid tumours are a morphologically diverse group of lesions that share histological similarity to the Spitz naevus, a benign melanocytic skin tumour. Distinguishing classic Spitz naevi from cutaneous malignant melanoma is usually achievable on standard histology sections, but occasionally equivocal lesions are encountered that show features intermediate between these two entities and consequently generate considerable clinical and histopathological concern. The nomenclature and diagnostic criteria for spitzoid lesions are not standardized and this article begins by considering the adverse effect this has on our understanding of spitzoid tumour biology. Investigations of some of the hallmark features of cancer and neoplasia in spitzoid tumours are described, and the contribution of these studies to our understanding of spitzoid tumour biology is considered, along with their potential diagnostic utility. These studies compare spitzoid tumours with better-characterized melanocytic lesions, and from such comparisons assumptions concerning the biological nature of different spitzoid tumours can be made. In contrast, investigations of the mitogen-activated protein kinase (MAPK) pathway and DNA gains and losses have suggested that Spitz naevi may be genetically distinct from other melanocytic tumours. The studies that led to this conclusion are reviewed, as well as subsequent work examining whether the same applies to all spitzoid tumours. Possible explanations for the considerable inconsistencies within some of these data are explored. Finally, potential pathways of tumour progression within spitzoid lesions are considered, with an emphasis placed upon insights gained from investigations of MAPK genes and DNA gains and losses.

[Malignant melanoma in children and adolescents]

According to data from the literature and to new data from the German central registry for malignant melanomas from the German Society of Dermatology, a summary is given about the occurrence of malignant melanoma in children and adolescents up to 18 years of age. During the first 10 years of life the occurrence of a melanoma is extremely rare, but slowly increases after the first decade. Several studies have shown that young people often have amelanotic tumors resembling pyogenic granuloma. This correlates with a histopathological high number of nodular melanomas in this age group. A reason might be a delay in the clinical diagnosis of malignant melanoma in children and young adults. Clinical and histopathological examples of melanoma in young people are demonstrated. Pitfalls in differential diagnosis and simulators of malignant melanoma are described and illustrated by examples of a medium sized congenital nevus with extensive intraepithelial spread of single melanocytes resembling a superficial spreading melanoma and by a compound nevus in association with a lichen sclerosus et atrophicus.

[Spitz nevus vs 'spitzoid' malignant melanoma. A diagnostic dilemma?]

Data from the literature and histopathological findings in six personal cases are used to illustrate criteria that can be applied in differential diagnosis between a Spitz nevus and a spitzoid variant of malignant melanoma. The diagnostic term 'atypical Spitz tumor' is explained; it is used to describe a morphological "grey zone" in which it is not possible to differentiate with adequate certainty between a Spitz nevus and a spitzoid malignant melanoma.