Genetic susceptibility to naevi--a twin study

Influence of germline genetic variants on dermoscopic features of melanoma

Nevus count is highly determined by inherited variants and has been associated with the origin of melanoma. De novo melanomas (DNMMs) are more prevalent in patients with a low nevus count and have distinctive dermoscopic features than nevus-associated melanomas. We evaluated the impact of nine single nucleotide polymorphisms (SNPs) of MTAP (rs10811629, rs2218220, rs7023329 and rs751173), PLA2G6 (rs132985 and rs2284063), IRF4 (rs12203592), and PAX3 (rs10180903 and rs7600206) genes associated with nevus count and melanoma susceptibility, and the MC1R variants on dermoscopic features of 371 melanomas from 310 patients. All MTAP variants associated with a low nevus count were associated with regression structures (peppering and mixed regression), blue-whitish veil, shiny white structures, and pigment network. SNPs of PLA2G6 (rs132985), PAX3 (rs7600206), and IRF4 (rs12203592) genes were also associated with either shiny white structures or mixed regression (all corrected p-values ≤ .06). Melanomas from red hair color MC1R variants carriers showed lower total dermoscopy score (p-value = .015) and less blotches than melanomas from non-carriers (p-value = .048). Our results provide evidence that germline variants protective for melanoma risk and/or associated with a low nevus count are associated with certain dermoscopic features, more characteristic of de novo and worse prognosis melanomas.

Melanoma Genomics

The incidence of cutaneous melanoma continues to increase in pale skinned peoples in Europe and elsewhere. Epidemiological studies identified genetically determined phenotypes such as pale skin, freckles and red hair, and sunburn as risk factors for this cancer. The development of many melanocytic naevi is also genetically determined and a strong melanoma risk phenotype. Not surprisingly then, genome wide association studies have identified pigmentation genes as common risk genes, and to a lesser extent, genes associated with melanocytic naevi. More unexpectedly, genes associated with telomere length have also been identified as risk genes. Higher risk susceptibility genes have been identified, particularly CDKN2A as the most common cause, and very rarely genes such as CDK4, POT1, TERT and other genes in coding for proteins in the shelterin complex are found to be mutated. Familial melanoma genes are associated with an increased number of melanocytic naevi but not invariably and the atypical naevus phenotype is therefore an imperfect marker of gene carrier status. At a somatic level, the most common driver mutation is BRAF, second most common NRAS, third NF1 and increasing numbers of additional rarer mutations are being identified such as in TP53. It is of note that the BRAF and NRAS mutations are not C>T accepted as characteristic of ultraviolet light induced mutations.

Nevus count associations with pigmentary phenotype, histopathological melanoma characteristics and survival from melanoma

Although nevus count is an established risk factor for melanoma, relationships between nevus number and patient and tumor characteristics have not been well studied and the influence of nevus count on melanoma-specific survival is equivocal. Using data from the Genes, Environment and Melanoma (GEM) study, a large population-based study of primary cutaneous melanoma, we evaluated associations between number of nevi and patient features, including sun-sensitivity summarized in a phenotypic index, and tumor characteristics. We also assessed the association of nevus count with melanoma-specific survival. Higher nevus counts were independently and positively associated with male gender and younger age at diagnosis, and they were inversely associated with lentigo maligna histology. We observed a borderline significant trend of poorer melanoma-specific survival with increasing quartile of nevus count, but little or no association between number of nevi and pigmentary phenotypic characteristics or prognostic tumor features.

The Genes and Genetics of Malignant Melanoma

Background:

Population-based studies have identified several clinical variables associated with an increased risk of developing cutaneous melanoma that include phenotype, amount of and response to sun exposure, and family history. However, these observations are of limited relevance to clinical practice as the risk associated with each factor is individually modest and the characteristics of these variables lack precision when applied to a particular individual.

Objective:

To review the literature regarding recent advances made in the understanding of the genes and genetics of clinical variables associated with an increased risk of melanoma.

Conclusion:

Variants of the MC1R (melanocortin-1 receptor) have been identified as major determinants of high-risk phenotypes, such as red hair and pale skin, and the ability to tan in response to UV exposure. Several studies also suggest that such variants may increase melanoma risk independent of their contribution to phenotype. A strong genetic basis for both nevus density and size has been demonstrated and the link between nevi and the development of MM has become better defined. Finally, germline defects in several genes involved in cell cycle regulation, namely, p16 and CDK4, have been demonstrated in many familial melanoma kindreds. This progress has introduced the prospect of genetic testing as a means of identifying a limited number of high-risk individuals who can be targeted with regular screening and education regarding UV exposure and skin self-examination. Ultimately, through rational genetic therapy targeted to correcting the underlying molecular defect, altering the natural history of melanoma development may be possible.

Genetic factors associated with naevus count and dermoscopic patterns: preliminary results from the Study of Nevi in Children (SONIC)

BACKGROUND

Melanocytic naevi are an important risk factor for melanoma. Naevi with distinct dermoscopic patterns can differ in size, distribution and host pigmentation characteristics.

OBJECTIVES

We examined MC1R and 85 other candidate loci in a cohort of children to test the hypothesis that the development and dermoscopic type of naevi are modulated by genetic variants.

METHODS

Buccal DNAs were obtained from a cohort of 353 fifth graders (mean age 10·4 years). Polymorphisms were chosen based on a known or anticipated role in naevi and melanoma. Associations between single-nucleotide polymorphisms (SNPs) and baseline naevus count were determined by multivariate regression adjusting for sex, race/ethnicity and sun sensitivity. Dermoscopic images were available for 853 naevi from 290 children. Associations between SNPs and dermoscopic patterns were determined by polytomous regression.

RESULTS

Four SNPs were significantly associated with increasing (IRF4) or decreasing (PARP1, CDK6 and PLA2G6) naevus count in multivariate shrinkage analyses with all SNPs included in the model; IRF4 rs12203952 showed the strongest association with log naevus count (relative risk 1·56, P < 0·001). Using homogeneous naevi as the reference, IRF4 rs12203952 and four other SNPs in TERT, CDKN1B, MTAP and PARP1 were associated with either globular or reticular dermoscopic patterns (P < 0·05).

CONCLUSIONS

Our results provide evidence that subsets of naevi defined by dermoscopic patterns differ in their associations with germline genotypes and support the hypothesis that dermoscopically defined subsets of naevi are biologically distinct. These results require confirmation in larger cohorts. If confirmed, these findings will improve the current knowledge of naevogenesis and assist in the identification of individuals with high-risk phenotypes.

Vitamin D and melanoma

Recreational sun exposure and sunburn are causal for melanoma but the risk is strongly genetically determined. Health promotion advice about sun protection should be aimed at susceptible individuals (pale skin, freckles, large numbers of melanocytic nevi and a family history). We discuss here the evidence that sun-sensitive people have lower vitamin D levels and that, in practice, it is very difficult for such individuals to achieve sufficient levels without supplementation in the UK at least. We conclude that melanoma susceptible sun-avoidant individuals should be advised to avoid insufficiency by supplementation.

Vitamin D is anti-proliferative in vitro for some melanoma cell lines. In a large melanoma cohort we have observed that lower serum 25-hydroxyvitamin D₂/D₃ levels at diagnosis were associated with thicker tumors and poorer prognosis (study as yet not validated). In the UK, melanoma patients commonly have sub-optimal 25-hydroxyvitamin D₂/D₃ levels at and post diagnosis; we discuss approaches to management of such patients based on some new data from our group.

Clinical and histological characteristics of melanocytic nevus in external auditory canals and auricles

Nevi, which consist of nevus cells arising from external auditory canals (EACs) and auricles, are rare and their characteristics are not thoroughly understood. The purpose of this study was to analyze the clinicopathological characteristics of melanocytic nevus (MN) in EACs and auricles. Medical records were reviewed in 35 cases with junctional, compound and intradermal nevi treated in Ajou University Hospital, Korea between 2001 and 2011. Patient demographic, location, shape, and diameter of nevi, and pathologic results were analyzed according to the location, EACs (23 cases) and auricles (12 cases). Female predominance was noted in both EAC (60.9 %, 14 cases) and auricular (75 %, 9 cases) nevi. The mean age of EAC nevi (37.1 years) was younger than that of auricular nevi (42.2 years). The chief complaint was a symptomless mass in both groups, mostly in dome-like gross appearances. The mean diameter of EAC and auricular nevi was 9.6 (3-16) mm and 12.2 (3-25) mm, respectively. Histological findings chiefly presented intradermal nevi in EACs (78.3 %) and auricles (83.3 %) which showed preference to older patients, in contrast to the compound type. All nevi including five cases with skin grafts were completely excised without any recurrence within the follow-up period (average 5.3 months). A possible dysplastic nevus was detected in only one case. All MNs in EACs or auricles reveal similar characteristics. Early and complete excision is recommended to avoid skin graft, functional problems, and the risk of malignant melanoma.

Prevalence and characteristics of choroidal nevi: the multi-ethnic study of atherosclerosis

OBJECTIVE

To describe the prevalence of choroidal nevi in 4 racial or ethnic groups (white, black, Hispanic, and Chinese) in the United States.

DESIGN

Cross-sectional study.

PARTICIPANTS

Participants of the second examination of the Multi-Ethnic Study of Atherosclerosis (MESA), involving 6176 persons 44 to 84 years of age without clinical cardiovascular disease at baseline selected from 6 United States communities.

METHODS

Fundus images were taken using a 45° digital camera through dark-adapted pupils and were graded for choroidal nevi using the modified Wisconsin Age-Related Maculopathy Grading System and the Blue Mountains Eye Study protocol.

MAIN OUTCOME MEASURES

Choroidal nevi.

RESULTS

The overall prevalence of choroidal nevi in the whole cohort was 2.1%, with prevalences higher in whites (4.1%) than blacks (0.7%), Hispanics (1.2%), and Chinese (0.4%; P<0.001 for any differences among groups). The lowest prevalence of choroidal nevi occurred in those 75 to 84 years of age. The nevi were subfoveal in 4% of eyes with nevi and were not associated with a decrease in visual acuity. Characteristics of the nevi (size, shape, location, color, drusen on surface) did not differ among racial or ethnic groups. With the exception of associations with higher C-reactive protein levels (odds ratio [OR] per mg/dl on the logarithmic scale, 1.23; 95% confidence interval [CI], 1.06-1.43; P = 0.01) and lower systolic blood pressure (OR per 10 mmHg, 0.90; 95% CI, 0.82-0.99; P = 0.04), choroidal nevi were not associated with other potential risk factors (e.g., gender, smoking status, alcohol consumption, lipid levels, coagulation factors, or kidney disease).

CONCLUSIONS

Low prevalences of choroidal nevi were found in the 4 groups participating in the MESA cohort, with whites having higher prevalence than the other racial or ethnic groups. The higher prevalence in whites than in other groups was not explained by any of the factors studied. When choroidal nevi were present, their characteristics did not differ among racial or ethnic groups.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Skin cancer screening behaviours among individuals with a strong family history of malignant melanoma

BACKGROUND

This study examined the prevalence and correlates of skin cancer screening behaviours among individuals at high risk of developing melanoma due to strong family history.

METHODS

A total of 120 individuals with a known family-specific CDKN2A mutation (72% response rate) completed a self-report questionnaire assessing annual frequency of skin self-examination (SSE), clinical skin examination (CSE) and a variety of potential demographic, clinical and psychosocial correlates.

RESULTS

In the past 12 months, 50% of participants reported engaging in SSE at least four times, and 43% of participants had undergone at least one CSE. Engagement in SSE was associated with doctor recommendation (β=1.77, P=0.001), confidence in one's ability to perform SSE (β=1.44, P<0.0001), positive beliefs about melanoma treatment (β=0.77, P=0.002) and intention to perform SSE in the future (β=1.69, P<0.0001). These variables accounted for 59% of the variance in SSE behaviour. Further, information-seeking style moderated the relationship between anxiety and SSE (β=1.02, P=0.004). Annual uptake of CSE was associated with doctor recommendation (β=2.21, P<0.0001) and intention to undergo CSE in the future (β=1.19, P=0.001).

CONCLUSION

In comparison with clinical guidelines, it appears that individuals at high risk of developing melanoma engage in suboptimal levels of skin surveillance. Improved doctor-patient communication, as well as psycho-education and behavioural support, may be viable means of improving early skin cancer detection behaviours in this high-risk population.

Melanocytic nevi, nevus genes, and melanoma risk in a large case-control study in the United Kingdom

BACKGROUND

Increased number of melanocytic nevi is a potent melanoma risk factor. We have carried out a large population-based case-control study to explore the environmental and genetic determinants of nevi and the relationship with melanoma risk.

METHODS

We report nevus phenotype in relation to differing patterns of sun exposure, inherited variation at loci shown in recent genome-wide association studies to be nevus genes, and risk.

RESULTS

Increased numbers of nevi were associated with holiday sun exposure, particularly on intermittently sun-exposed body sites (test for P(trend) < 0.0001). Large nevi were also associated with holiday sun exposure (P = 0.002). Single nucleotide polymorphisms (SNP) on chromosomes 9 and 22 were associated with increased numbers of nevi (P = 0.04 and P = 0.002 respectively) and larger nevi (P = 0.03 and P = 0.002), whereas that on chromosome 6 was associated only with large nevi (P = 0.01). Melanoma risk was associated with increased nevus count, large nevi, and atypical nevi for tumors in all body sites (including rare sites) irrespective of age. The risk persisted when adjusted for inheritance of nevus SNPs.

CONCLUSIONS

The at-risk nevus phenotype is associated with behaviors known to increase melanoma risk (holiday sun exposure). Although SNPs on chromosomes 6, 9, and 22 were shown to be nevus genes, they explained only a small proportion of melanoma risk and nevus phenotype; therefore, several nevus genes likely remain to be identified.

IMPACT

This article confirms the importance of nevi in melanoma pathogenesis and increases understanding of their genetic determinants.

Estimating CDKN2A carrier probability and personalizing cancer risk assessments in hereditary melanoma using MelaPRO

Personalized cancer risk assessment remains an essential imperative in postgenomic cancer medicine. In hereditary melanoma, germline CDKN2A mutations have been reproducibly identified in melanoma-prone kindreds worldwide. However, genetic risk counseling for hereditary melanoma remains clinically challenging. To address this challenge, we developed and validated MelaPRO, an algorithm that provides germline CDKN2A mutation probabilities and melanoma risk to individuals from melanoma-prone families. MelaPRO builds on comprehensive genetic information, and uses Mendelian modeling to provide fine resolution and high accuracy. In an independent validation of 195 individuals from 167 families, MelaPRO exhibited good discrimination with a concordance index (C) of 0.86 [95% confidence intervals (95% CI), 0.75-0.97] and good calibration, with no significant difference between observed and predicted carriers (26; 95% CI, 20-35, as compared with 22 observed). In cross-validation, MelaPRO outperformed the existing predictive model MELPREDICT (C, 0.82; 95% CI, 0.61-0.93), with a difference of 0.05 (95% CI, 0.007-0.17). MelaPRO is a clinically accessible tool that can effectively provide personalized risk counseling for all members of hereditary melanoma families.

Management of familial melanoma and nonmelanoma skin cancer syndromes

The clinical manifestations of hereditary skin cancer syndromes depend upon the interplay between environmental and genetic factors. Familial melanoma occurs in the setting of hereditary susceptibility, with a complex phenotype of early age of onset, multiple atypical moles, multiple primary melanomas, multiple melanomas in the family, and in some instances pancreatic cancer. Identification of individuals who may have a hereditary susceptibility for the development of melanoma is essential to provide an opportunity for primary prevention, and to target high-risk groups for early diagnosis and treatment. Consequently, the surgeon as one of the primary caregivers should be familiar with hereditary skin cancer syndromes and their pathogenesis, diagnosis, management, and surveillance recommendations. This article discusses a practical approach for some of the issues likely encountered by the surgeon in the management of familial melanoma and non-melanoma skin cancer.

A pooled analysis of melanocytic nevus phenotype and the risk of cutaneous melanoma at different latitudes

An abnormal nevus phenotype is associated with an increased risk of melanoma. We report a pooled analysis conducted using individual nevus data from 15 case-control studies (5,421 melanoma cases and 6,966 controls). The aims were to quantify the risk better and to determine whether relative risk is varied by latitude. Bayesian unconditional logistic random coefficients models were employed to study the risk associated with nevus characteristics. Participants with whole body nevus counts in the highest of 4 population-based categories had a greatly increased risk of melanoma compared with those in the lowest category (pooled odds ratio (pOR) 6.9 (95% confidence interval (CI): 4.4, 11.2) for those aged<50 years and pOR 5.1 (95% CI: 3.6, 7.5) for those aged>or=50). The pOR for presence compared with absence of any clinically atypical nevi was 4.0 (95% CI: 2.8, 5.8). The pORs for 1-2 and >or=3 large nevi on the body compared with none were 2.9 (95% CI: 1.9, 4.3) and 7.1 (95% CI: 4.7, 11.6), respectively. The relative heterogeneities among studies were small for most measures of nevus phenotype, except for the analysis of nevus counts on the arms, which may have been due to methodological differences among studies. The pooled analysis also suggested that an abnormal nevus phenotype is associated most with melanomas on intermittently sun-exposed sites. The presence of increased numbers of nevi, large nevi and clinically atypical nevi on the body are robust risk factors for melanoma showing little variation in relative risk among studies performed at different latitudes.

High- and average-risk individuals' beliefs about, and perceptions of, malignant melanoma: an Australian perspective

Despite expanding knowledge regarding the genetics of melanoma, there have been few attempts to define the psychosocial experiences of individuals with a family history of this disease. This study explored the ways in which individuals at varying levels of risk perceive, and respond to, melanoma. Forty semi-structured interviews were undertaken with affected (n = 20) and unaffected (n = 20) individuals with or without a family history of melanoma. Data were analysed for potential thematic differences between risk groups, genders, and intentions to pursue genetic testing for melanoma risk. Overall, participants with a family history were in acceptance of their increased risk status and had developed ways of coping without major disruption to their daily lives. However, some participants expressed ambiguity regarding the causes of melanoma and the effectiveness of health behaviours such as sun protection. Major thematic patterns identified for those intending to pursue genetic testing were: negative emotional associations with melanoma; an emphasis on screening and sun avoidance, but not sun protection; and heightened perceptions of personal susceptibility to melanoma. In contrast, thematic patterns identified for those likely to decline testing were: ready access to stories of melanoma survival; and an emphasis on the causal role of sun exposure, whilst still believing that genetic factors may contribute to melanoma susceptibility. Compared to males, females reported a greater tendency to completely avoid the sun in order to reduce their melanoma risk. The data provide preliminary evidence for the importance of identifying misconceptions that may impede informed decision-making about genetic testing for melanoma risk.

Genome-wide linkage scan for atypical nevi in p16-Leiden melanoma families

In most Dutch melanoma families, a founder deletion in the melanoma susceptibility gene CDKN2A (which encodes p16) is present. This founder deletion (p16-Leiden) accounts for a significant proportion of the increased melanoma risk. However, it does not account for the Atypical Nevus (AN) phenotype that segregates in both p16-Leiden carriers and non-carriers. The AN-affected p16-Leiden family members are therefore a unique valuable resource for unraveling the genetic etiology of the AN phenotype, which is considered both a risk factor and a precursor lesion for melanoma. In this study, we performed a genome-wide scan for linkage in four p16-Leiden melanoma pedigrees, classifying family members with five or more AN as affected. The strongest evidence for an atypical nevus susceptibility gene was mapped to chromosome band 7q21.3 (two-point LOD score=2.751), a region containing candidate gene CDK6.

Melanocytic nevi in 2783 children and adolescents in Turkey

This study investigated the numbers of melanocytic nevi in Turkish children and adolescents. The research was conducted on 2783 subjects (age range, 7-14 yrs) at three elementary schools in Malatya, Turkey (latitude 38 degrees N). Numbers of melanocytic nevi per subject were counted using a standard international protocol. Comparisons were made with subjects categorized according to age, sex and skin type. The mean melanocytic nevus count was 1.07 +/- 2.37. A significant positive correlation was found between nevus count and age (p < 0.001). The mean count for boys was significantly higher than that for girls (p < 0.001). Subjects with skin type II had a higher mean melanocytic nevus count than the other three groups. This is the first study related to numbers of melanocytic nevi in Turkey. The findings reveal that Turkish children and adolescents have few melanocytic nevi compared to those elsewhere in the world. In line with previous reports on other populations, analysis showed that older age, skin type II, and male sex are associated with higher melanocytic nevus counts. The results underline the importance of ethnic background in melanocytic nevus development.

Study of health outcomes in school children: key challenges and lessons learned from the Framingham Schools' Natural History of Nevi Study

BACKGROUND

We describe the planning, recruitment, key challenges, and lessons learned in the development of a study of the evolution of nevi (moles) among children in a school setting.

METHODS

This population-based study of digital photography and dermoscopy of the child's back (overview, close-up, and dermoscopic images) and genetic specimens took place among fifth graders in the Framingham, Massachusetts School System. Schoolchildren and their parents completed baseline surveys on sun protection practices, sunburns, and past ultraviolet exposures, including summer and vacation experiences.

RESULTS

Prestudy outreach was conducted with children, parents, nurses, administrators, and pediatricians. Of the 691 Framingham families with a fifth grader (aged 10-11), 443 consented to complete surveys and undergo digital photography and dermoscopy during the school's routine scoliosis testing. Of the 443 families providing consent, 369 agreed to genetic testing. We identified key factors to consider when implementing school-based studies: (a) pilot studies to demonstrate feasibility, (b) inclusion of school administration and parents, (c) grassroots approach with multiple contacts, and (d) embedding research studies within preexisting school health services.

CONCLUSIONS

Launching an observational study within the school environment required an academic/school collaboration across numerous disciplines including dermatology, epidemiology, genetics, medical photography, school health, community health education, and most notably, the need for the presence of a full-time study nurse in the school. A large school system proved to be an excellent resource to conduct this first prospective study on the evolution of moles in US schoolchildren. The key challenges and lessons learned may be applicable to other investigators launching school-based initiatives.

Management of familial melanoma

Relatives of patients with melanoma are at increased risk of melanoma. We review the evidence that this risk may be attributed both to shared susceptibility genes (both high-penetrance and lower-penetrance genes) and shared environment. The most frequent high-penetrance susceptibility gene is CDKN2A, and environmental effects on the risk to gene carriers are evident in that CDKN2A penetrance is higher in CDKN2A-mutation-positive families living in Australia than those in Europe. We review the approaches to managing melanoma families, in which the likelihood of there being detectable CDKN2A mutations is positively correlated with the number of cases of melanoma in the family. Within families, risk that an individual carries a germline mutation can be estimated by pedigree analysis for autosomal dominant genes with incomplete penetrance. Prevention advice to families relates to moderation of sun exposure and self-examination of naevi, although there are few supportive data.

The effect of sun exposure in determining nevus density in UK adolescent twins

We report a study of 221 teenage twin pairs to examine the genetic and environmental determinants of nevi representing the most potent phenotypic risk factor for melanoma. Our published heritability analysis estimated that nevi are mainly genetically determined. In this paper we examine the role of sun exposure. We report a correlation between nevus density and sun exposure, particularly that acquired in hotter countries than in the UK (mean nevus density 41 per m2 in those in the highest quartile of exposure vs 24 per m2 in those with no exposure, p<0.0001). We were not able to demonstrate a protective effect for either sun protection cream or shirt wearing. By including phenotypic variables and reported sun exposure into the heritability analysis, we conclude that 66% of the total variance of nevus count is attributable to genetic effects: 7% associated to eye color, 6% to hair color, and 1% to reported skin type, which leaves 52% as to yet unidentified genetic factors. Of the 25% of variation attributable to environmental influences, one-third is estimated to be because of sun exposure on hot holidays.

Ectopic expression of tyrosinase increases melanin synthesis and cell death following UVB irradiation in fibroblasts from familial atypical multiple mole and melanoma (FAMMM) patients

Patients with familial atypical multiple mole and melanoma (FAMMM) [so-called familial dysplastic naevus syndrome (FDNS)] have a high risk for the development of malignant melanoma. The underlying gene defect has an autosomal dominant inheritance with variable expression and incomplete penetrance. Fibroblasts derived from FAMMM patients have high sensitivity to UVC and mutagens, e.g. 4-nitroquinoline-1-oxide. We were interested in identifying how the combination of inherent sensitivity to UV light and abnormal melanin synthesis interacts in the development of melanoma in FAMMM patients. Intermediates of melanin synthesis produce free radicals that are toxic to cells. Atypical moles (dysplastic naevi) are engaged in the biosynthesis of abnormal melanin pigments. This study examined whether there was any abnormal melanin pigmentation or cell damage after the ectopic expression of tyrosinase in fibroblasts from FAMMM patients when compared with fibroblasts from normal subjects. Fibroblasts from FAMMM patients (3012T and 3072T) were associated with a higher sensitivity than normal human fibroblasts to the toxicity of UVB. When cells were infected with tyrosinase-expressing adenovirus (Ad-HT) and irradiated with UVB, FAMMM fibroblasts showed higher tyrosinase activity, produced more melanin pigments and were degraded more significantly than normal human fibroblasts. Western blot analysis revealed that Ad-HT-infected 3072T produced a larger amount of tyrosinase protein than did Ad-HT-infected normal fibroblasts after UVB irradiation. Our findings suggest: (1) that FAMMM fibroblasts have an unknown machinery which enhances tyrosinase expression by UVB irradiation; and (2) that the resulting increase in melanin synthesis affects the cytotoxicity of UVB to FAMMM fibroblasts. All of these processes may be involved in the genomic instability and development of melanoma in FAMMM patients.

The Relationship Between the Epidermal Growth Factor (EGF) 5′UTR Variant A61G and Melanoma/Nevus Susceptibility

The inheritance of a G allele in position 61 in the 5'UTR of the epidermal growth factor (EGF) gene has been reported to increase melanoma susceptibility, a finding we have investigated in this study. The most potent phenotypic risk factor for melanoma is the atypical mole syndrome (AMS) phenotype. Our hypothesis is that the AMS is genetically determined and that nevus genes are also low penetrance melanoma susceptibility genes. We report that the G allele frequencies were the same in 697 healthy women and 380 melanoma cases (OR 0.97, 95% CI 0.8-1.2 p=0.76). We therefore found no evidence that this polymorphism is a melanoma susceptibility gene. Furthermore, we found no evidence that the polymorphism controls the nevus phenotype (nevus number, number atypical nevi or AMS phenotype). We did find some evidence that the G allele may be associated with decreased tumor Breslow thickness (OR 0.5, 95% CI 0.3-0.9) for the A/A genotype versus A/G and G/G combined in tumors of thickness >3.5 vs < or =3.5 mm and may therefore act as a predictor of survival, although this finding is not in accord with the original report. This is the second study to find no association between EGF +61 and melanoma susceptibility.

UV light from 290 to 325 nm, but not broad-band UVA or visible light, augments the formation of melanocytic nevi in a guinea-pig model for human nevi

We have previously described a guinea-pig model where pigmented nevi similar to human nevi can be produced by application of low-dose topical 7,12-dimethylbenzanthracene (DMBA) followed by solar-simulated light. Five groups of guinea-pigs were used to test the effect of various spectral bands of solar-simulated light on low-dose DMBA-induced melanocytic nevi. Animals were irradiated with either UVB to near UVA2 (290-325 nm), UVA, visible light, full solar spectrum or no irradiation three times per wk for 12 mo to determine the broad-band effect of nevi-inducing irradiation. There was a significant increase in nevi/animal in the UVB-treated group (mean 1.53) compared with all groups (versus UVA 0.3, p<0.001; versus visible light 0.24, p<0.001; versus full spectrum (UVB+UVA+visible) 0.68, p=0.02; versus control (nil irradiation) 0.37, p=0.01). No differences in skin thickness were found between any group (p=0.11). In conclusion, we present a report of the active waveband of melanocytic nevi induction; where UVB to near UVA2 is the likely responsible waveband. Furthermore, because there was a significant decrease in nevi/animal receiving the full solar spectrum compared with the UVB group, it is possible that broad-band UVA and or visible light may be inhibitory wavebands for nevi induction.

Turner's syndrome in dermatology

Turner's syndrome (TS) is a common genetic disorder of girls and women, for which the defining clinical triad is short stature, impaired sexual development, and infertility. Although classically known as monosomy X, genetic heterogeneity is frequent in TS, with mosaicism conferring a survival advantage. Several genetic loci have been implicated in TS including the short stature homeobox gene. TS effects many organs, with cutaneous stigmata providing critical clues for early detection of TS. The presence of lymphedema and its cutaneous sequelae are predictive of other systemic disorders, such as cardiac disease. Although an increased number of benign nevi have been reported in TS, the decreased melanoma rate in this population suggests some protective factor is active. Keloids were thought to be prevalent in TS, but recent data suggest otherwise. Autoimmune diseases are common in TS, with a possible increased prevalence of alopecia areata and vitiligo. The following review discusses new insights into the genetics and pathogenesis of this complex disorder, summarizes the major systemic effects, and reviews skin manifestations of TS and their implications.

Familial melanoma: a complex disorder leading to controversy on DNA testing

The initial enthusiasm generated by the discovery of the first susceptibility gene found for melanoma has slightly dampened over recent years. For the majority of melanoma families the underlying gene defect is still not known, so the search for other melanoma genes is continuing. Also, the increased risk of melanoma does not seem to be restricted to mutation carriers, but is present even in non-mutation carriers in melanoma families. The underlying defect of familial melanoma is less straightforward than previously thought; both environmental and hereditary risk modifiers intermingle in a perplexing way. This makes familial melanoma a complex disorder which deserves the close attention of both clinicians and researchers, especially as the opinion on gene testing in familial melanoma has not yet achieved consensus. On the one hand, there is a rising demand from families for genetic testing; on the other hand, there is the clinicians' concern about the value of such testing.

Acquired melanocytic nevi as risk factor for melanoma development. A comprehensive review of epidemiological data

Acquired melanocytic nevi (MN) in Caucasian populations are important markers for the risk of melanoma development. The total number of MN on the whole body is the most important independent risk factor for melanoma and the risk of melanoma development increases almost linearly with rising numbers of MN. Additionally, the presence of atypical MN and of actinic lentigines are likewise independent risk factors for melanoma. Atypical mole syndrome should be defined by the presence of many acquired MN and a threshold number of atypical MN. Acquired MN develops mainly during childhood and adolescence in the first two decades of life. The number of acquired nevi seems to be related to hereditary factors and nevus-prone families exist. The amount of sun exposure is the most important environmental risk factor for nevus development, particularly in early childhood. Interestingly, sunburns may play a role in nevus development, but seem not to be required, and even moderate sun exposure promotes the process. Therefore, preventive measures for nevus and melanoma development should target young children and adolescents.

Moderate sun exposure and nevus counts in parents are associated with development of melanocytic nevi in childhood: a risk factor study in 1,812 kindergarten children

BACKGROUND

Melanocytic nevi have been identified as the most important risk factor for cutaneous melanoma. Sun exposure, sunburns, and light pigmentation have been found to be associated with their development in childhood. To the authors' knowledge, nevus proneness of parents and the exact type of ultraviolet (UV) exposure have not yet been investigated in this context. The authors' objective was to determine independent risk factors and their impact for nevus development in childhood.

METHODS

The current study was conducted by two university departments of dermatology in 49 public nursery schools in Stuttgart, Germany and in 38 public nursery schools in Bochum, Germany. The cross-sectional study included 1,812 children aged 2-7 years and their parents. Total body nevus counts in children, assessment of pigmentary features, and nevus counts on the arms of parents were performed. Parents underwent a standardized interview concerning national origin and lifestyle features, as well as habits and magnitude of sun exposure of children. Analysis was performed by multivariate linear regression analysis and by multiple logistic regression analysis.

RESULTS

The number of nevi was found to steadily increase with age from a median of 3 at age 2 years to 19 at age 7 years (P < 0.0001). High numbers of nevi in children were associated with the number of weeks on sunny holidays, outdoor activities at home, skin type, facial freckling, ethnicity of parents, and the number of nevi on the arms of parents. Previously experienced sunburns failed significance (P = 0.0620).

CONCLUSIONS

The authors found a strong association between nevus development in children and the number of parental moles, which most likely points to an inherited factor. Moderate sun exposure such as outdoor activities during a German summer without sunburns seemed to be sufficient for induction of melanocytic nevi. The authors believe that these findings will have direct impact on concepts for preventive strategies.

Sun exposure and number of nevi in 5- to 6-year-old European children

The occurrence and number of melanocytic nevi are among the most important known risk factors for the development of malignant melanoma. Studying the causes of nevi should lead to successful strategies in the prevention of melanoma. Among 11,478 white German children of preschool age the association between benign melanocytic nevi and a number of risk factors for skin cancer was examined. We found that subjects with a reported history of increased sun exposure, for example, painful sunburns, and an increased number of holidays in foreign countries with a sunny climate had significantly higher nevus counts than individuals without these characteristics. Our results provide further evidence that nevus counts may not only be part of a genetic predisposition but also a result of increased exposure to ultraviolet radiation. Together with the fact that a high nevus count is the most relevant risk factor for malignant melanoma, the results strongly indicate a connection between UV-radiation and the development of melanocytic skin cancer. In conclusion, strategies to reduce the incidence of melanoma should begin with young children.

The dilemma of the dysplastic nevus

There are few areas in dermatology that provoke as much controversy as dysplastic nevus. Over the past decade, there have been significant strides made in terms of understanding the biology and etiology of the lesion. Distinct and reliable clinical and histologic features have been delineated. In this article, the management of patients with dysplastic nevi and the role for dermoscopy, photographic surveillance, genetic mapping and counseling, chemoprevention, and nevi removal are discussed.

An assessment of the CDKN2A variant Ala148Thr as a nevus/melanoma susceptibility allele

Melanocytic nevi are the most potent risk factors for melanoma yet identified. Variation in the nevus phenotype within a population is predominantly genetically determined. Genes that determine nevus expression may therefore act as low penetrance melanoma susceptibility genes. Rare germline mutations in CDKN2A predispose to melanoma and appear to be nevogenic, although the correlation between nevus phenotype and mutation status is poor. It is plausible that more common CDKN2A variants may influence both melanoma susceptibility and nevus susceptibility. Ala148Thr is a G to A missense polymorphism of CDKN2A, which is found in 4%-6% of the general population. We have investigated the role of Ala148Thr as a low penetrance melanoma or nevus susceptibility allele in two separate groups of individuals. The first was a sample of 488 adults recruited from 179 families of patients with the atypical nevus phenotype and/or a family history of melanoma, and the second was a population-based sample of 599 women. Similar prevalences of Ala148Thr (4.9% and 5.2%) were found in both samples but significant variation in the prevalence of the polymorphism was seen across geographic areas within England. There was no association between Ala148Thr status and nevus number or history of melanoma, and therefore the results did not support the hypothesis that the Ala148Thr variant is a low penetrance melanoma or nevus susceptibility allele. A significant protective role of Ala148Thr on the number of atypical nevi was observed in the family sample (mean of 1 atypical nevus in those with the allele and 3.5 nevi in those without, p = 0.02). After allowing for potential confounders this was not evident in the population-based sample.

The density of melanocytic nevi correlates with constitutional variables and history of sunburns: a prevalence study among Italian schoolchildren

In several studies from northern Europe, north America and Australia, melanocytic nevi are correlated with pigmentary traits and with intense sun exposure in a way similar to malignant melanoma. However, it is unclear if these data can be extrapolated to populations in other geographic locations and with different prevalent phenotypes. Our study was conducted among schoolchildren aged 13-14 years in 16 Italian cities. The parents of 3,127 children of a total of 3,160 (99%) consented to our study. A structured questionnaire was used to collect information about sun exposure and lifetime history of sunburns. Children were also examined by trained dermatologists to assess pigmentary traits and to make a count of melanocytic nevi. The median nevus density was higher among boys than girls. Areas that are usually chronically exposed to the sun exhibited a higher density of nevi compared to intermittently and rarely exposed areas. A higher density of nevi was found in children with lighter skin, blond hair and blue eyes. Red-haired children had a remarkably lower nevus density compared to the other color categories. The density of nevi increased with an increased number of reported episodes of sunburns. The results concerning nevi >/=6 mm in diameter paralleled those obtained for the total nevus density. However, at variance with total nevus density, a significant relation was also observed between larger nevi and freckling. Our study confirms that, in Italian schoolchildren, there is a relation between pigmentary traits, history of sunburns and the density of melanocytic nevi. Melanocytic nevi and malignant melanoma share a similar risk factor profile.

Genetic and environmental factors in cutaneous malignant melanoma

Cutaneous malignant melanoma (CMM) is an interesting example of multifactorial disease, where both genetic and environmental factors are involved and interact. Major risk factors include a personal and familial history of melanoma, cutaneous and pigmentary characteristics, sun exposure and reactions to sun exposure. Phenotypic risk factors are likely to be genetically determined. Two high-risk melanoma susceptibility genes-CDKN2A and CDK4-have been identified to date, with a third gene p14(ARF) also being suspected of playing a role. Other high-risk genes are anticipated by the existence of 9p21-unlinked families. A low-risk melanoma-susceptibility gene-MC1R-has also been identified. Current studies aim to identify other susceptibility genes as well as to determine the respective contributions and interactions of the various genetic and environmental factors of CMM and associated phenotypes.

Genetics and the common cancers

Rare highly penetrant genes cannot account for much of the familial risk for most common cancers, and there is increasing evidence that a high proportion of cancers arise in a susceptible minority who carry low-penetrance genes or gene combinations. The evidence for the existence of such genes and the prospects for identifying them are reviewed.

The epidemiology of UV induced skin cancer

There is persuasive evidence that each of the three main types of skin cancer, basal cell carcinoma (BCC), squamous cell carcinoma (SCC) and melanoma, is caused by sun exposure. The incidence rate of each is higher in fairer skinned, sun-sensitive rather than darker skinned, less sun-sensitive people; risk increases with increasing ambient solar radiation; the highest densities are on the most sun exposed parts of the body and the lowest on the least exposed; and they are associated in individuals with total (mainly SCC), occupational (mainly SCC) and non-occupational or recreational sun exposure (mainly melanoma and BCC) and a history of sunburn and presence of benign sun damage in the skin. That UV radiation specifically causes these skin cancers depends on indirect inferences from the action spectrum of solar radiation for skin cancer from studies in animals and the action spectrum for dipyrimidine dimers and evidence that presumed causative mutations for skin cancer arise most commonly at dipyrimidine sites. Sun protection is essential if skin cancer incidence is to be reduced. The epidemiological data suggest that in implementing sun protection an increase in intermittency of exposure should be avoided, that sun protection will have the greatest impact if achieved as early as possible in life and that it will probably have an impact later in life, especially in those who had high childhood exposure to solar radiation.

The association between idiopathic scoliosis and the number of acquired melanocytic nevi

BACKGROUND

Several syndromes in which melanocytic nevi and scoliosis were present in the same patient have been described. No control study has been made to date to determine whether there is a relationship between these disorders.

OBJECTIVE

We attempted to demonstrate the association between acquired melanocytic nevi (AMN) and idiopathic scoliosis (IS).

METHODS

We studied 93 patients with IS, aged 10 to 18 years, from our hospital. Controls were randomly selected from 2 schools; Adam's forward bending test was used to exclude persons with clinical scoliosis, and the control group finally comprised 101 pupils. An observational, cross-sectional study was done. All AMN 2 mm or larger observed on the body were counted by one dermatologist. Other variables reported as risk factors in the number of nevi were also considered. Reliability of AMN counts was previously demonstrated.

RESULTS

The median number of AMN was 18 (range, 10-42) in the IS group and 8 (range, 3-13) in controls (P <.001). The persons with scoliosis had more non-AMN dermatologic lesions than the controls (P <.05). Light phenotype correlated with many AMN. On multivariate analysis only scoliosis and age accounted independently for the number of AMN.

CONCLUSION

IS is associated with many AMN. Multiple AMN may become a diagnostic marker for IS, and these two malformations might constitute a syndromic association.

Detecting low penetrance genes in cancer: the way ahead

The search for the genes responsible for many complex genetic diseases is well under way and has already been successful in some cases. The study of cancer as a complex genetic disease has lagged behind other conditions, largely because of particular problems that are associated with malignant disease. Cancer also, however, presents specific opportunities for gene identification, which are not found in many other diseases. While the methods of genetic mapping and gene cloning used for other complex diseases will be applied to cancer, these must almost certainly be complemented by other methods, such as the study of somatic mutations, cancer associated phenotypes, and modifier genes for Mendelian cancers. Here, we review the strategies available for identifying cancer predisposition genes of low and moderate penetrance.

The genetics of hereditary melanoma and nevi. 1998 update

Although the first English-language report of melanoma in 1820 contained a description of a melanoma-prone family, it was 1983 before formal genetic analysis suggested an autosomal dominant mode of inheritance for both melanoma and the then newly described melanoma precursor, dysplastic nevi (DN). Subsequent genetic studies have assumed this model to be correct, although when viewed in aggregate, the data are inconsistent. The first proposed melanoma gene (CMM1) was mapped to chromosome 1p36. This gene assignment has not been confirmed. A second melanoma gene, designated CMM2, has been mapped to chromosome 9p21. This gene assignment has been confirmed, and the cell cycle regulator CDKN2A has been proposed as the candidate gene. Germline mutations in this gene have been identified in about 20% of melanoma-prone families that have been studied to date. Pancreatic cancer occurs excessively in melanoma families with germline mutations in CDKN2A. Germline mutations in the cyclin-dependent kinase gene CDK4 (chromosome 12q14) have been described in three melanoma families. This finding represents a third melanoma gene but one that accounts for only a tiny fraction of all hereditary melanoma. Recently, a familial melanoma-astrocytoma syndrome has been reported. Large germline deletions of 9p21 occur in these families, with the p19 gene implicated in its pathogenesis. At present, clinical predictive genetic testing for mutations in the CDKN2A gene is available commercially, but its use has been limited by uncertainty as to how test results would affect the management of melanoma-prone family members. Currently, management recommendations include monthly skin self-examination, clinical skin examination once or twice yearly, a low threshold for simple excision of changing pigmented lesions, moderation of sun exposure, and appropriate use of sunscreens. A heritable determinant for total nevus number has been suggested by twin studies. Other data suggest the presence of a major gene responsible for "total nevus density" in melanoma-prone families. Approximately 55% of the mole phenotype in multiplex melanoma families was explained by this proposed gene. An autosomal dominant mode of inheritance has been proposed for DN, and data exist to suggest that DN may be a pleiotropic manifestation of the 1p36 familial melanoma gene. However, there clearly are melanoma-prone families that do not express the dysplastic nevus trait, and some of the families linked to CDKN2A also present with dysplastic nevi. Several studies have shown a surprisingly high prevalence of DN on the skin of family members of probands with DN. In light of the extensive evidence documenting that persons with DN (both sporadic and familial) have an increased prospective risk of melanoma, these family studies suggest that relatives of persons with DN should be examined for both DN and melanoma. Genetic determinants play a major role in the pathogenesis of normal nevi, DN, and melanoma. Identifying the molecular basis of these genetic events promises to enhance melanoma risk-reduction strategies and, ultimately, reduce melanoma-associated mortality.

A major quantitative-trait locus for mole density is linked to the familial melanoma gene CDKN2A: a maximum-likelihood combined linkage and association analysis in twins and their sibs

Important risk factors for melanoma are densely clustered melanocytic nevi (common moles) and mutations in the p16 (CDKN2A) gene. Nevi may be subclassified as raised or flat. In our sample, raised nevi were 27% of the total, and the two kinds had a correlation of.33. Correlations for total-nevus count (TNC) in 153 MZ and 199 DZ twin pairs were.94 and.60, respectively, which are compatible with a very-high degree of genetic determination. We hypothesized that some of the genetic variance might be due to variation in the p16 gene. Analysis of linkage to a highly polymorphic marker (D9S942), located close to p16, detected quantitative-trait-loci (QTL) effects accounting for 27% of variance in TNC, rising to 33% if flat but not raised moles were considered. Total heritability was higher for raised (.69) than for flat (.42) moles, but QTL linkage was 0 for raised moles, whereas it accounted for 80% of the heritability of flat moles; additionally, family environment accounted for only 15% of variance in raised versus 46% in flat moles. These findings suggest that raised and flat nevi have very different etiologies. Longer alleles at D9S942 were associated with higher flat-mole counts, and a novel modification to a within-sibship association test showed that this association is genuine and not due to population stratification, although it accounts for only 1% of total variance. Since germline mutations in the exons of CDKN2A are rare, it is likely that variants in the noncoding regions of this gene, or in another gene nearby, are responsible for this major determinant of moliness and, hence, of melanoma risk.

Tumor progression, early diagnosis and prognosis of melanoma

Primary melanomas evolve from melanocytes or from precursor lesions through two stages: the radial and vertical growth phases. The radial growth phase may be in situ or microinvasive, but is a non-tumorigenic neoplastic process, while the vertical growth phase is tumorigenic. The prognosis in radial growth phase is excellent irrespective of thickness or other variables. Curable radial growth phase melanomas can be recognized by surveillance of patients identified by screening for risk markers which include dysplastic nevi, common nevi, freckles, and other indicators of chronic or acute sun exposure or sun sensitivity. The prognosis in vertical growth phase depends on attributes of the tumor and of the host. The tumor mitotic rate, the presence of host tumor-infiltrating lymphocytes (TIL) within the vertical growth phase, and tumor thickness are the most powerful predictors of survival. New prognostic attributes are needed not only to provide for more accurate prognosis and diagnosis, but also to test the relevance of in vitro or animal studies in a human neoplastic system. Such attributes will be developed in the future based on markers that are associated with tumor progression. Candidate markers include growth factors and cytokines and their receptors, adhesion molecules and their ligands, chemotactic and motility factors, immune response-related molecules, and tumor-associated proteases. Some of these markers that are represented in the transition from radial to vertical growth phase will be reviewed. The tumor progression model presented here has been of value in the development of more accurate prognostic models, and in the elucidation of mechanisms of the malignant phenotype in melanoma.

Genetic predisposition to ocular melanoma

Uveal melanoma is the most common primary intraocular malignancy, with an annual incidence of 6 per million. The environmental factors known to increase the risk of cutaneous melanoma appear to be less important in ocular melanoma and it is conceivable that host factors have a greater impact. The coexistence of ocular and cutaneous melanoma in some patients suggests a predisposition to both types and implicates mutations in the CDKN2A gene in a proportion of these cases. An association between ocular melanoma and breast and/or ovarian cancer has also been reported and recent studies of breast cancer families strongly implicate BRCA2 as a predisposition gene. Other more common genes predisposing to ocular melanoma may be of low penetrance. An example of a gene in this class is MC1R, which affects host response to ultraviolet radiation. Identification of genes conferring an increased risk of ocular melanoma should provide insights into the pathogenesis of this tumour. Furthermore, it offers an opportunity to identify individuals at a high risk who may benefit from targeted surveillance. At present the identification of such individuals is restricted to the small number belonging to BRCA2 families and those with the atypical mole syndrome.

Maternal and child constitutional factors and the frequency of melanocytic naevi in children

This study examined the association between numbers of benign melanocytic naevi in 7-year-old children in Oxfordshire born in 1988-9 with their mother's arm naevus count, and maternal and child pigmentation factors. We believe this is the first time that the relationship between child and maternal naevus counts has been reported. A high naevus count in the child was associated with male sex (P = 0.009), freckling (P = 0.001) and propensity of the child to burn in the sun (P = 0.05). A low naevus count was observed in red-haired children (P = 0.02). The strongest association of child's naevus count was with a high maternal arm naevus count, independent of the child's pigmentation factors (trend P < 0.0001). Maternal pigmentation factors were not associated with child's naevus count independent of the child's own pigmentation factors. Maternal arm naevus counts may be a better predictor of child naevus count than the child's own pigmentation factors and children. There has not been examination, however, of the relationship between naevus counts in children and those in their parents. We therefore conducted a study of the occurrence of naevi in children aged 7-8 years in Oxfordshire, examining, in addition to sex and pigmentation factors in the child, the relationship of maternal pigmentation factors and maternal naevus counts with naevi in their offspring.

FGF expression allows nevus cells to survive in three-dimensional collagen gel under conditions that induce apoptosis in normal human melanocytes

Melanocytes, the pigment forming cells of the skin, form an almost nonproliferating cell population located to the lowermost part of the epidermis. Normally melanocytes are not found higher in the epidermis or in the dermis. Nevi consist of melanocytes with altered growth characteristics and localization. The common pigmented nevus, a benign skin lesion, develops when melanocytes proliferate in the dermo-epidermal junction or in the dermis. Here we report growth characteristics of in vitro cultured normal human melanocytes and dermal nevus-derived melanocytes. As previously reported, nevus cells have a moderate to high FGF-2 expression level. Here we demonstrate that dermal nevus cells are able to survive in three-dimensional type 1 collagen culture, while normal human melanocytes rapidly undergo apoptosis. Melanocytes also, however, survive in collagen cultures in the presence of exogenous FGF-2. The survival of nevus cells in collagen is suppressed by protamine, an inhibitor of FGF-mediated cell stimulation. The in vivo growth environment of dermal nevus cells consists largely of type I and type III collagens. The results suggest that FGF-2 expression by nevus cells allows them to adapt to grow in the dermis. FGF-2 obviously has importance as a melanocyte survival factor and probably also in the development of malignant melanoma.

The association between naevi and melanoma in populations with different levels of sun exposure: a joint case-control study of melanoma in the UK and Australia

Two case-control studies were set up to investigate the relationship between melanocytic naevi and risk of melanoma and to compare the naevus phenotype in two countries exposed to greatly different levels of sun exposure and different melanoma rates. In England 117 melanoma cases and 163 controls were recruited from the North-East Thames Region and 183 melanoma cases and 162 controls from New South Wales, Australia. Each subject underwent a whole-body naevus count performed by the same examiner in each country. Relative risks associated with melanocytic naevi in each country were calculated with comparison of naevus data in controls between Australia and England. Atypical naevi were strong risk factors for melanoma in both countries: the odds ratio (OR) for three or more atypical naevi was 4.6 (95% CI 2.0-10.7) in Australia compared with 51.7 (95% CI 6.5-408.4) in England. Common naevi were also significant risk factors in Australia and England with similar odds ratios in the two countries. Prevalence of atypical naevi was greater in Australian controls than in English controls: OR 9.7 (95% CI 1.2-81.7) for three or more atypical naevi in Australia compared with England. For young age groups, the median number of common naevi was greater in Australia than in the UK, whereas for older individuals this difference in naevi number between the two countries disappeared. The prevalence of naevi on non-sun-exposed sites in controls was not significantly different between the two countries. The atypical mole syndrome (AMS) phenotype was more prevalent in Australian controls (6%) than in English controls (2%). The results of this study support the role of sun exposure in the induction of atypical naevi in adults. There was a trend towards stronger risk factors associated with atypical naevi in England compared with Australia. The atypical mole syndrome, usually associated with a genetic susceptibility to melanoma, was more common in Australia than in England, suggesting genetic environmental interactions with the possibility of phenocopies induced by sunlight.

Genetics of cutaneous melanoma and nevi

To provide a state-of-the-art summary of currently available data about the genetics of cutaneous melanoma and nevi, we reviewed the pertinent literature and outlined the important findings on genetic analyses. Although the first English-language report of melanoma in 1820 contained a description of a melanoma-prone family, seminal studies by investigators at the National Cancer Institute and the University of Pennsylvania identified dysplastic nevi (DN) as an important melanoma precursor, suggested an autosomal dominant mode of inheritance for both melanoma and DN, and proposed that a melanoma-susceptibility gene (CMM1) was located on chromosome 1p36. This gene assignment has not yet been confirmed by independent investigators. A second melanoma gene, designated CMM2, has been mapped to chromosome 9p21. This gene assignment has been confirmed independently, and the cell cycle regulator p16INK4a has been proposed as a candidate gene; germline mutations in this gene have been identified in about half of melanoma-prone families. Germline mutations in the cyclin-dependent kinase gene CDK4 (chromosome 12q14) have recently been described in two melanoma kindreds; this finding likely represents a third melanoma gene. A heritable determinant for total nevus number has been suggested, as has the presence of a major gene responsible for total nevus density in melanoma-prone families. An autosomal dominant mode of inheritance for DN has been proposed, and evidence suggests that DN may be a pleiotropic manifestation of the 1p36 familial melanoma gene. Several studies have shown a surprisingly high prevalence of DN on the skin of family members of probands with DN. In light of the extensive evidence documenting that persons with DN (both sporadic and familial) have an increased prospective risk for melanoma, these family studies suggest that relatives of persons with DN should be examined for DN and for melanoma. Overall, genetic determinants have a major role in the pathogenesis of normal nevi, DN, and melanoma. Elucidating the molecular basis of these genetic events promises to enhance melanoma risk reduction strategies and thereby reduce melanoma-associated mortality.

Genetic and epidemiological risk factors for a malignant melanoma-predisposing phenotype: the great number of nevi

Multiple genetic and epidemiological factors are involved in the etiology of cutaneous malignant melanoma. The phenotype defined by a great number of nevi (GNN) is consistently reported as being a major risk factor for melanoma and is likely to be under genetic control. As part of a large genetic and epidemiologic survey of melanoma in France, our goal was to understand the pattern of inheritance of GNN in 295 nuclear families ascertained through 295 melanoma probands. The GNN phenotype was defined as having 50 or more nevi vs. less than 50 nevi. Four percent of the 295 families included at least 2 GNN cases. We found that sun exposure during holidays and propensity to sunburns were significantly associated with GNN, independent of the occurrence of melanoma. Four segregation analyses of GNN were conducted, using the class D regressive logistic model, which differed according to the sampling procedure chosen (with and without the melanoma probands) and the inclusion or not of the significant risk factors. Three of these analyses led to the detection of a recessive-like major factor, which did not fit a Mendelian pattern of inheritance in two of them. Our results are discussed with respect to the low familial clustering of GNN, the type of analysis conducted, the characteristics of the model used, and the complexity of the mechanisms underlying the GNN phenotype.