Melanocytic naevi and melanoma: an epidemiological perspective

Defining the Molecular Genetics of Dermoscopic Naevus Patterns

Melanocytic naevi are common melanocytic proliferations that may simulate the appearance of cutaneous melanoma. Naevi commonly harbour somatic mutations implicated in melanomagenesis but in most cases lack the necessary genomic alterations required for melanoma development. While the mitogen-activated protein kinase pathway and ultraviolet radiation strongly contribute to naevogenesis, the somatic mutational landscape of dermoscopic naevus subsets distinguishes some of the molecular hallmarks of naevi in relation to melanoma. We herein discuss the classification of naevi and theories of naevogenesis and review the current literature on the somatic alterations in naevi and melanoma. This review focusses on the clinical-dermoscopic-pathological and genomic correlation of naevi that shapes the current understanding of naevi.

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.

High nevus counts confer a favorable prognosis in melanoma patients

A high number of nevi is the most significant phenotypic risk factor for melanoma and is in part genetically determined. The number of nevi decreases from middle age onward but this senescence can be delayed in patients with melanoma. We investigated the effects of nevus number count on sentinel node status and melanoma survival in a large cohort of melanoma cases. Out of 2,184 melanoma cases, 684 (31.3%) had a high nevus count (>50). High nevus counts were associated with favorable prognostic factors such as lower Breslow thickness, less ulceration and lower mitotic rate, despite adjustment for age. Nevus count was not predictive of sentinel node status. The crude 5- and 10-year melanoma-specific survival rate was higher in melanomas cases with a high nevus count compared to those with a low nevus count (91.2 vs. 86.4% and 87.2 vs. 79%, respectively). The difference in survival remained significant after adjusting for all known melanoma prognostic factors (hazard ratio [HR] = 0.43, confidence interval [CI] = 0.21-0.89). The favorable prognostic value of a high nevus count was also seen within the positive sentinel node subgroup of patients (HR = 0.22, CI = 0.08-0.60). High nevus count is associated with a better melanoma survival, even in the subgroup of patients with positive sentinel lymph node. This suggests a different biological behavior of melanoma tumors in patients with an excess of nevi.

Congenital melanocytic nevi

This article reviews congenital melanocytic nevi (CMN), which are present at birth or appear shortly thereafter, and their main histologic features. Several histologic variants and histopathologic criteria that differentiate CMN from other nevi, such as atypical or dysplastic nevi, and from nevoid malignant melanoma, are discussed. Histologic pitfalls in the correct identification of lentiginous melanocytic hyperplasia, pagetoid scatter, and proliferative nodules in the context of CMN are discussed. The risk for development of malignant melanoma in association with a congenital melanocytic nevus and variable causes for changing mole are discussed.

Dermoscopic naevus patterns in people at high versus moderate/low melanoma risk in Queensland

INTRODUCTION

Dermoscopic understanding of naevus characteristics is essential baseline knowledge for identifying early malignant changes.

METHOD

This cross-sectional study includes 34 patients (56% female, mean age 48 years) at high risk of melanoma (personal or a first degree family member with history of melanoma) and 31 moderate/low melanoma risk volunteers (55% female, mean age 37 years) recruited at the Princess Alexandra Hospital, Brisbane, between October 2009 and March 2010. Participants received full body and individual dermoscopic imaging of clinically significant naevi (≥2 mm on the back of male/female and lower limbs of female and ≥5 mm at other body sites). Dermoscopic patterns of naevi were compared between people at high versus moderate/low melanoma risk according to age and body site.

RESULTS

In both high and moderate/low risk groups, globular naevi predominated on the head/neck and abdomen/chest, reticular and non-specific naevi on the back, and non-specific pattern on the upper and lower limbs. Non-specific naevi were the most common in all age groups. In both risk groups, globular naevi were more frequent in the younger age bracket, and reticular naevi were more frequent in the older age bracket. Mixed naevus patterns were infrequent and were more common in the younger age brackets of both risk groups.

CONCLUSION

Our preliminary data shows that dermoscopic naevus patterns were similar for age and body site in people at different levels of melanoma risk, suggesting high melanoma risk does not influence dermoscopic naevus patterns.

Latitude gradient for melanoma incidence by anatomic site and gender in Norway 1966-2007

Latitude gradients and time trends for cutaneous malignant melanoma (CMM) were analyzed using incident cases from the Norwegian Cancer Registry for the period 1966-2007. Sex and various anatomic regions of the body were taken into account, for better understanding of the role of ultraviolet radiation in CMM etiology. There is a latitude gradient for CMM on all body sites included in the present study, with 2-2.5 times higher incidence rates in the south. The latitude gradients seem to be largest for the trunk. Melanomas on sites intermittently exposed to the sun (like the trunk) dominate both in the north and in the south and this distribution has not changed over the years. A leveling off of the incidence rates are observed for both sexes and for all sites studied, after 1985-1995, slightly more in the south than in the north, except for the head and neck where the incidence rates have continued to increase slowly in the north as well as in the south. The leveling off of melanoma trend is probably associated with melanoma prevention campaigns and with increasing awareness, although vitamin D could play a role.

Congenital Melanocytic Nevi

This article reviews congenital melanocytic nevi (CMN), which are present at birth or appear shortly thereafter, and their main histologic features. Several histologic variants and histopathologic criteria that differentiate CMN from other nevi, such as atypical or dysplastic nevi, and from nevoid malignant melanoma, are discussed. Histologic pitfalls in the correct identification of lentiginous melanocytic hyperplasia, pagetoid scatter, and proliferative nodules in the context of CMN are discussed. The risk for development of malignant melanoma in association with a congenital melanocytic nevus and variable causes for changing mole are discussed.

Nevus Size and Number Are Associated with Telomere Length and Represent Potential Markers of a Decreased Senescence In vivo

Nevus counts represent one of the strongest risk factors for melanoma. They appear in childhood and adolescence and involute from middle age onwards. Recent evidence has shown that nevus cells undergo oncogene-induced senescence involving the p16/retinoblastoma pathway. However, telomere length also influences senescence in proliferative somatic cells and varies between individuals. This study explores whether telomere length measured in white cells is associated with nevus count and size in 1,897 Caucasian women ages 18 to 79 years. Total body nevus counts were positively correlated with white cell telomere length (mean, 7.09 kbp; range, 5.09-9.37) after adjustment for age (P = 0.0001). Age-adjusted telomere length was also associated with nevus count for nevi above 5 mm in diameter (P = 0.04). Subjects in the top category for nevus count had an average age-adjusted telomere length 150 bp longer than those in the lowest category. The positive correlation between white cell telomere length and nevi number and size may reflect an increased replicative potential (reduced senescence) in individuals with longer telomeres, which may not be melanocyte specific. Understanding mechanisms influencing the induction and involution of nevi will not only help in understanding the pathophysiology of melanoma but should also shed light on the complex relationship between aging and cancer.

Molecular characterization of a t(9;12)(p21;q13) balanced chromosome translocation in combination with integrative genomics analysis identifiesC9orf14as a candidate tumor-suppressor

A large number of nevi (LNN) is a high risk phenotypic trait for developing cutaneous malignant melanoma (CMM). In this study, the breakpoints of a t(9;12)(p21;q13) balanced chromosome translocation were finely mapped in a family with LNN and CMM. Molecular characterization of the 9p21 breakpoint identified a novel gene C9orf14 expressed in melanocytes disrupted by the translocation. Integrative analysis of functional genomics data was applied to determine the role of C9orf14 in CMM development. An analysis of genome-wide DNA copy number alterations in melanoma tumors revealed the loss of the C9orf14 locus, located proximal to CDKN2A, in approximately one-fourth of tumors. Analysis of gene expression data in cancer cell lines and melanoma tumors suggests a loss of C9orf14 expression in melanoma tumorigenesis. Taken together, our results indicate that C9orf14 is a candidate tumor-suppressor for nevus development and late stage melanoma at 9p21, a region frequently deleted in different types of human cancers.

Nevi in children: a practical approach to evaluation

Education is the cornerstone of melanoma prevention. Well-child examinations are an excellent opportunity to educate patients and parents about melanoma risk factors and prevention. The only modifiable risk factor for the development of melanoma and acquisition of nevi is level of sun exposure. Every patient who is evaluated for a melanocytic lesion should be educated about sun avoidance during midday, protective clothing including long-sleeved shirts, long pants, and hats with brims, and playing in shaded areas when outdoors. Proper application and appropriate uses of sunscreen should also be reviewed.

Benign epithelial ovarian tumours-cancer precursors or markers for ovarian cancer risk?

The natural history of the development of epithelial ovarian cancer remains obscure and no effective screening test exists. In several human malignancies progression from benign to invasive tumour occurs, but this sequence has not been established for epithelial ovarian cancer. We have reviewed epidemiological, histopathological and molecular studies of benign epithelial ovarian tumours to assess the evidence for and against such a progression in ovarian cancer. These data suggest that a diagnosis of a benign ovarian cyst or tumour is associated with an increased risk of ovarian cancer later in life. Current evidence also suggests that benign serous tumours can progress to low-grade serous cancer and that benign mucinous tumours can progress to mucinous cancer. The more common high-grade serous ovarian cancers are likely to arise de novo.

A genome-wide scan for naevus count: linkage to CDKN2A and to other chromosome regions

High numbers of melanocytic naevi (moles), and mutations in the p16 gene (CDKN2A), are two strong risk factors for cutaneous malignant melanoma. We have previously reported linkage of mole count to the CDKN2A locus. Here, we report genome-wide scans for mole counts (differentiated into flat, raised and atypical subtypes) with a total of 796 microsatellite markers for 424 families with 1024 twins and siblings, plus genotypes for 690 parents. Inclusion of 221 pairs of MZ twins enabled separation of shared environmental and polygenic influences, so placing an upper limit to estimates of QTL variance. Maximum likelihood multipoint variance component methods were used to assess linkage of naevus count. Sex, age, body surface area, skin colour, hair colour, sunburn and facial freckles were included as covariates. Peak linkage of flat mole count was to regions on chromosomes 2, 9, 8 and 17 with lod scores 2.95, 2.95, 2.50 and 2.15, respectively. The support for linkage to the CDKN2A gene region (9p21) increased to 3.42 when additional fine mapping markers were added. For raised mole count, there was suggestive evidence of linkage in our sample to chromosome 16 (lod=1.87), and for atypical mole count on chromosomes 1, 6 and X with lod scores of 2.20, 2.00 and 2.00, respectively. The multivariate linkage peaks generally match those from individual trait analyses, with the exception of a new peak on chromosome 4 (point-wise empirical P-value=0.001). We replicate our earlier finding of linkage to CDKN2A and discovering linkage to several novel regions that may also influence risk of the development of malignant melanoma.

Genome-wide search for nevus density shows linkage to two melanoma loci on chromosome 9 and identifies a new QTL on 5q31 in an adult twin cohort

The density of acquired melanocytic nevi represents an important risk factor for malignant melanoma. Total body nevus counts were collected in a cross-sectional study of 1730 healthy females from the UK Adult twin registry comprising 709 dizygous and 156 monozygous pairs. Nevus density (ND) increased up to the age of 35 years and then gradually declined. Quantitative genetic analysis showed a smaller genetic influence (36%) on ND up to 35 years, compared with after 35 years where it rose to 59%. Using a sub-sample of 1238 genotyped individuals, we performed distinct genome-wide scans for individuals above and below 35 separately. In the younger sub-sample, we confirmed a quantitative trait locus (QTL) for ND on chromosomes 9p21 (LOD=2.54), a region already linked to both familial melanoma and ND. We also observed a linkage signal on 9q21 (LOD=2.55) overlapping a recently reported susceptibility locus for ocular and cutaneous melanoma in Danish families. The strongest evidence of linkage identified a novel QTL on chromosome 5q31-32 (LOD=3.47). None of these linkages was observed in the group aged 35 years and over, which showed suggestive linkage on chromosome 2p24 (LOD=2.75). To the best of our knowledge, this is the first genome-wide search for ND in a large sample of healthy adults. The results suggest that different sets of genes are likely to influence the processes leading to the appearance of nevi and their involution. They provide both novel and replicated QTLs for nevus development, some of which might overlap with those for melanoma and warrant detailed investigation.

Melanocytic nevi in very young children: the role of phenotype, sun exposure, and sun protection

BACKGROUND

Melanocytic nevi are strongly associated with cutaneous melanoma, yet little is known about factors influencing nevus development in the first years of life.

OBJECTIVE

We sought to identify phenotypic and environmental factors associated with nevus counts in very young children.

METHODS

In a cluster prevalence survey, full body nevus counts and phenotypic assessments were conducted on 193 children aged 1 to 3 years. Information on each child's sun exposure and sun protection practices was obtained through parental questionnaire.

RESULTS

High total nevus counts were associated with heavy facial freckling, time spent outdoors on weekends in summer, and Caucasian ethnicity. Low nevus counts were associated with dark skin color, ability to tan, and frequent application of sunscreen. Frequent wearing of hats was specifically associated with low nevus counts on the face, but not at other sites.

CONCLUSIONS

Nevi are common at a very young age among children in Queensland, Australia, and are associated with sun exposure and freckling. Diligent sun protection practices appear to reduce nevus burden, even after accounting for the effects of phenotype and sun exposure factors. Primary prevention strategies aimed at reducing sun exposure in very early life may be effective in reducing nevus prevalence and melanoma risk.

Meta-analysis of risk factors for cutaneous melanoma: I. Common and atypical naevi

A systematic meta-analysis of observational studies of melanoma and one of the most important risk factors, the number of naevi, was conducted in order to clarify aspects of the aetiology of this disease. Following a systematic literature search, relative risks (RRs) were extracted from 46 studies published before September 2002. Dose-response random effects models were used to obtain pooled estimates. Sub-group analysis and meta-regression were carried out to explore sources of between-study variation and bias. Sensitivity analyses investigated the reliability of the results and any publication bias. Number of common naevi was confirmed an important risk factor with a substantially increased risk associated with the presence of 101-120 naevi compared with <15 (pooled Relative Risk (RR) = 6.89; 95% Confidential Interval (CI): 4.63, 10.25) as was the number of atypical naevi (RR = 6.36 95%; CI: 3.80, 10.33; for 5 versus 0). The type of study and source of cases and controls were two study characteristics that significantly influenced the estimates. Case-control studies, in particular when the hospital was the source for cases or controls, appeared to present much lower and more precise estimates than cohort studies.

Risk of melanoma arising in large congenital melanocytic nevi: a systematic review

Large congenital melanocytic nevi are cutaneous lesions regarded by many as premalignant; estimates of malignancy incidence range from 0 to 42 percent. Given the often complex and extensive nature of large congenital melanocytic nevi resection and reconstruction, the risk of malignant transformation is a crucial factor that surgeons and families must weigh when deciding whether or not to excise the lesion. The authors conducted a systematic analysis of data from the existing literature to critically evaluate the published studies and to establish a crude incidence rate for the risk of malignant melanoma transformation in large congenital melanocytic nevi. After a comprehensive literature search, they analyzed data from eight studies (containing a total of 432 large congenital melanocytic nevi patients) of sufficient scientific quality. Twelve patients (2.8 percent) in this sample developed cutaneous malignant melanoma during the reported follow-up periods. Using a subset of this data and comparing the incidence rates to those of the Surveillance, Epidemiology, and End Results population-based database using a standardized morbidity ratio, the authors found that the large congenital melanocytic nevi patients had an increased risk of melanoma (standardized morbidity ratio, 2599; 95 percent confidence interval, 844 to 6064) compared with the general population. Regarding treatment before developing melanoma in the 12 patients, 50 percent were observed before diagnosis, 17 percent had partial excision, 8.3 percent had dermabrasion, 8.3 percent had a chemical peel, and 17 percent did not have any treatment information. These combined data are clinically useful when consulting with the parents of children with large congenital melanocytic nevi and in the management of older patients with existing lesions. This study shows that there is a significantly increased risk of melanoma in large congenital melanocytic nevi patients. The data also reveal the need for a standardized definition of large congenital melanocytic nevi and a long-term, prospective outcomes study to determine the true lifetime risk of melanoma in patients with and without surgical excision.

Evolution of melanocytic nevi on the faces and necks of adolescents: a 4 y longitudinal study

All melanocytic nevi on the faces and necks of a cohort of students, initially aged 12-14 y, were mapped and photographed annually for 4 y. The features of each nevus were charted yearly noting changes in size and profile, and the appearance or disappearance of any nevi on a student's face and neck was recorded. Nevi were classified by size (small, < 2 mm; medium, 2-5 mm; large, > 5 mm), and by profile (flat, raised). Data from 20 adolescents selected randomly from the cohort for detailed analysis showed males had about twice as many nevi as females, but there was little difference between sexes in their patterns of nevus development. Approximately half the nevi were small in all years; under 5% were large. Over the 4 y of follow-up the proportion of flat nevi dropped from 70% to 57%, whereas nevus numbers increased by 47% in year 1, with smaller increases in older students. Most new or disappearing nevi were small and flat, although both incident and disappearing nevi could be larger and/or raised. Of the existing nevi that altered in the follow-up period, the tendency was towards an increase in size among raised but not among flat nevi; a lowering of profile among small nevi; and a raising of profile among larger nevi; but there were many exceptions to this pattern. Among several host factors examined, inability to tan after sun exposure was found to be significantly negatively associated with the propensity of nevi to change size over the study period. Overall our findings indicate that, contrary to conventional belief, there is a measurable turnover among melanocytic nevi even in early life.

Sun exposure and interaction with family history in risk of melanoma, Queensland, Australia

Sun exposure is the main environmental risk factor for melanoma, but the timing of exposure during life that confers increased risk is controversial. Here we provide the first report of the association between lifetime and age-specific cumulative ultraviolet exposure and cutaneous melanoma in Queensland, Australia, an area of high solar radiation, and examine the association separately for families at high, intermediate and low familial melanoma risk. Subjects were a population-based sample of melanoma cases diagnosed and registered in Queensland between 1982 and 1990 and their relatives. The analysis included 1,263 cases and relatives with confirmed cutaneous melanoma and 3,111 first-degree relatives without melanoma as controls. Data on lifetime residence and sun exposure, family history and other melanoma risk factors were collected by a mailed questionnaire. Using conditional multiple logistic regression with stratification by family, cumulative sun exposure in childhood and in adulthood after age 20 was significantly associated with melanoma, with estimated relative risks of 1.15 per 5,000 minimal erythemal doses (MEDs) from age 5 to 12 years, and 1.52 per 5 MEDs/day from age 20. There was no association with sun exposure in families at high familial melanoma risk. History of nonmelanoma skin cancer (relative risk [RR] = 1.26) and multiple sunburns (RR = 1.31) were significant risk factors. These findings indicate that sun exposure in childhood and in adulthood are important determinants of melanoma but not in those rare families with high melanoma susceptibility, in which genetic factors are likely to be more important.

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.

Use of sunscreen is linked with elevated naevi counts in Israeli school children and adolescents

Epidemiological evidence indicates that a fair complexion and exposure to solar radiation in early years contribute to the proliferation of naevi and subsequent melanoma risk. To determine whether protection from sunlight is associated with lower naevi counts, we examined the prevalence and risk factors of naevi in a sample of Israeli school pupils. Whole body counts of naevi were recorded in 974 out of 1312 (74.2%) recruited pupils (7 and 12 year olds) from Ramat-Gan and Jerusalem. Host characteristics and habits of sun exposure were obtained using questionnaires. In each age group and geographic area, the mean whole body naevi counts, adjusted for confounders, were higher among males, pupils of European-American descent, and those susceptible to sunburn. The contributions to naevi risk of fair skin colour and frequent recreational sun exposure were higher among 7 year olds. Regular sunscreen use contributed to the naevi risk for both age strata in Ramat-Gan (at age 7, rate ratio [RR] = 1.7, 95% confidence interval [CI] = 1.3-2.2; at age 12, RR = 1.5, 95% CI = 1.1-2.1). Among the younger age group in Ramat-Gan, even seldom compared with no use of sunscreen was associated with higher naevi counts (RR= 1.5, 95% CI = 1.2-2.0). Similar patterns were noted with the pupils from Jerusalem. In conclusion, the elevated naevi count with increased sunscreen use indicates that sunscreens apparently do not modify the genetic predisposition to naevi proliferation. For better protection of children and adolescents, including those who use sunscreens, from the naevogenic effect of solar radiation, they should be encouraged to limit their exposure and wear protective clothing when in the sun.

Genetic and environmental contributions to size, color, shape, and other characteristics of melanocytic naevi in a sample of adolescent twins

The presence of melanocytic naevi is the strongest known risk factor for malignant melanoma. We have developed a computer imaging system with which it is possible to make quantitative measures of the size, color, and shape of pigmented lesions. The objective of this study was to examine the genetic and environmental contributions to these characteristics of naevi as measured by computer image analysis in a sample of adolescent twins. We captured video images of the 5 most atypical pigmented skin lesions (i.e., the largest, darkest, or most irregularly shaped) on each individual from 322 Australian adolescent twin pairs. Features extracted by computer image analysis for each lesion included color, size, symmetry, elongation, boundary irregularity, and edge distinctness. We found major genetic influences on the color and size of lesions accounting for between 40 and 80% of total variance. There were significant components of shared environmental influence (22-45% of total variance) for the color variables, with sun exposure the most obvious explanation. Differences between individuals in naevus color and size are largely genetic in origin although there are significant environmental contributions to color as well.

Teaching non-specialist health care professionals how to identify the atypical mole syndrome phenotype: a multinational study

The atypical mole syndrome (AMS) phenotype is the strongest known risk factor for cutaneous melanoma but recognition of the phenotype has been claimed to be problematic and to require specialist assessment. This study determined the ability of previously unskilled doctors and nurses in five countries to recognize the phenotype after brief training. The system used was the AMS scoring system. This incorporates melanocytic naevus counts, clinical atypia of naevi and distribution of naevi. The agreement in scoring between the dermatologist and trained personnel was determined in 986 patients; overall agreement in diagnosis was 94.5% (kappa 0.70, P < 0.0001). The kappa scores in different countries ranged from 0.65 to 0.77 for individual naevus characteristics, indicative of good agreement. Accurate diagnosis of the atypical mole syndrome phenotype is possible by non-specialists. This has implications for collaborative studies of naevi, for screening and for both primary and secondary prevention of melanoma.

Melanocortin-1 receptor polymorphisms and risk of melanoma: is the association explained solely by pigmentation phenotype?

Risk of cutaneous malignant melanoma (CMM) is increased in sun-exposed whites, particularly those with a pale complexion. This study was designed to investigate the relationship of the melanocortin-1 receptor (MC1R) genotype to CMM risk, controlled for pigmentation phenotype. We report the occurrence of five common MC1R variants in an Australian population-based sample of 460 individuals with familial and sporadic CMM and 399 control individuals-and their relationship to such other risk factors as skin, hair, and eye color; freckling; and nevus count. There was a strong relationship between MC1R variants and hair color and skin type. Moreover, MC1R variants were found in 72% of the individuals with CMM, whereas only 56% of the control individuals carried at least one variant (P<.001), a finding independent of strength of family history of melanoma. Three active alleles (Arg151Cys, Arg160Trp, and Asp294His), previously associated with red hair, doubled CMM risk for each additional allele carried (odds ratio 2.0; 95% confidence interval 1. 6-2.6). No such independent association could be demonstrated with the Val60Leu and Asp84Glu variants. Among pale-skinned individuals alone, this association between CMM and MC1R variants was absent, but it persisted among those reporting a medium or olive/dark complexion. We conclude that the effect that MC1R variant alleles have on CMM is partly mediated via determination of pigmentation phenotype and that these alleles may also negate the protection normally afforded by darker skin coloring in some members of this white population.

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.

Clinical recognition of melanoma and its precursors

This article reviews the essential clinical features of cutaneous melanoma, as well as those of the more common benign pigmented lesions that need to be distinguished on clinical examination.

The risk of melanoma in patients with congenital nevi: a cohort study

BACKGROUND

Giant congenital nevi are associated with a greatly increased risk of melanoma, but this has not been quantified. Smaller congenital nevi are believed by some authors to be associated with increased risk, but this is uncertain and needs to be clarified.

OBJECTIVE

Our purpose was to analyze cause-specific mortality and cancer incidence risks in patients with congenital nevi according to size of the nevi.

METHODS

We followed up 265 patients with congenital nevi first treated at the Hospital for Sick Children or at St. John's Hospital in London during 1950 to 1984 for mortality to mid-1993 and for cancer incidence from 1971 to 1989. Mortality and cancer incidence rates in the cohort were compared with expectations from national mortality and cancer incidence rates by sex, age, and calendar period.

RESULTS

Among the 33 patients with a congenital nevus covering at least 5% of the body area, two melanomas occurred during follow-up; both were fatal. The relative risk of melanoma mortality in these patients was 1046 (95% confidence interval, 127 to 3779). In the remaining 232 patients, 68 of whom had a nevus covering 1% to 4% of the body, and 164 with nevi smaller than 1% of body area, no melanomas occurred (0.18 melanoma deaths expected). The difference in melanoma mortality risk between the group with a nevus covering at least 5% of the body and the group with smaller nevi was significant (p < 0.05). There was not a significantly increased risk of nonmelanoma mortality or of nonmelanoma cancer incidence overall in the cohort, although two lymphohematopoietic malignancies occurred.

CONCLUSION

The data show the large risk of melanoma in patients with nevi covering more than 5% of the body surface area. The results do not support the hypothesis of greatly increased risk in persons with congenital nevi smaller than this, but because the confidence intervals of the result were wide, the data are compatible with a sizable risk. Much larger studies than those that have so far been undertaken, or combined analysis of data from several studies, are needed to quantify more precisely the risk of melanoma in relation to size of nevi and to determine the appropriate clinical management of these lesions.

Risk of developing cutaneous malignant melanoma in atypical-mole syndrome: New York University experience and literature review

The presence of atypical moles (AM) is considered to be a marker for an increased risk of developing cutaneous malignant melanoma (MM). The extent to which individuals with the atypical-mole syndrome (AMS) are at risk for developing MM is unknown. We present a review of the world literature and of our experience at New York University. We conclude that the presence of AMS in Caucasians significantly increases the risk of developing MM, regardless of geographic location. A further increase in MM risk is noted if there is a personal and/or family history of MM.

Reliability of naevus counts in identifying individuals at high risk of malignant melanoma

The majority of deaths from malignant melanoma could be prevented by regular screening of at-risk individuals. However, the feasibility of introducing active screening programmes depends on the reliability of criteria for identifying those individuals who are at increased risk. Several case-control studies indicate that one of the most important risk factors is the number of benign pigmented naevi. This criterion might constitute a practical means of identifying individuals suitable for inclusion in an active screening programme. The aim of this study was to assess the reliability of using naevus counts as an indicator of risk. Two possible methods of assessment were compared: assessment by trained interviewers, and assessment by experienced dermatologists. The results suggest that this criterion may not be as practical or reliable as originally anticipated. Interviewer naevus counts correlated poorly with dermatologists' assessments (kappa = 0.19). Counts by dermatologists of the number of naevi on the left arm differed by up to nine naevi, although most counts were within four naevi of each other. There was reasonable correlation between naevus counts on the left arm and those on the whole body (r = 0.71). However, the relationship was not perfect. Selection of individuals for screening solely based on the number of naevi on the left arm may exclude many people with high total body counts but relatively low left arm counts.

Prepubertal melanoma in a medium-sized congenital naevus

A case of malignant melanoma in a medium-sized congenital naevus in a prepubertal girl is presented. Risk factors for developing melanoma during childhood include giant congenital naevi, dysplastic naevus syndrome and xeroderma pigmentosum. The lifetime risk of melanoma associated with giant congenital naevi has been estimated to be 4%-20%; the risk associated with small and medium-sized congenital naevi however remains controversial. In the latter lesions, malignant transformation is considered an almost exclusively postpubertal phenomenon, in contrast to giant congenital naevi where it often occurs prior to puberty. In our patient, malignant transformation in a medium-sized congenital naevus occurred before puberty. We suggest that the true incidence of malignant transformation within these lesions and the time at which it occurs, should be documented by prospective studies and that not only the giant congenital naevi but also the smaller congenital naevi should be considered for prophylactic excision in early childhood.

Precursor lesions of melanoma: do they exist?

The question of whether definite precursors to melanoma exist is answered in the affirmative. Three cutaneous lesions likely to be such precursors are described and discussed as to their clinical and histologic appearance and incidence. Additionally, a type of conjunctival melanosis that has been associated with malignant melanoma of the conjunctiva is discussed and an attempt is made to define it; a proposed classification of this entity is reviewed. Basic approaches to management and analysis of precursor lesions are elaborated.

Interclinician agreement on the recognition of selected gross morphologic features of pigmented lesions. Studies of melanocytic nevi V

BACKGROUND

Since the late 1970s clinical criteria for dysplastic melanocytic nevi (DMN) have been proposed and discussed. However, to our knowledge, no rigorous quantitative evaluation of the ability of examiners to agree on the gross morphologic features ascribed to DMN or atypical melanocytic lesions in general has been conducted.

OBJECTIVE

The purpose of the study was to determine rates of interclinician agreement for recognizing seven clinical features associated with melanocytic lesions.

METHODS

The gross morphologic features of 156 pigmented lesions, judged to be the clinically most atypical, from 156 consecutively examined patients with cutaneous melanoma were analyzed. Independent of the other clinicians' examinations, four physicians (two medical oncologists, one internist-epidemiologist, and one dermatologist-dermatopathologist) recorded seven gross morphologic features of the most atypical pigmented lesion on each patient. For up to 122 patients, the rates of interobserver agreement on recognizing these clinical features were measured by intraclass correlation.

RESULTS

Among the clinical features assessed, the examiners noted macular components in 85.7% to 96.3% of lesions, asymmetry in 47.2% to 79.5%, irregular borders in 55.1% to 80.2%, ill-defined borders in 40.1% to 83.9%, and haphazard color in 40.8% to 73.9% of lesions. Despite this range of variance among examiners, there were statistically significant rates of interclinician agreement for the recognition of the latter features. There was less agreement in assessing individual colors within lesions.

CONCLUSION

These findings substantiate that certain gross morphologic features routinely used in the clinical evaluation of melanocytic lesions can be recognized with a significant degree of reliability.

Genetic susceptibility to naevi--a twin study

The risk of malignant melanoma to an individual is strongly related to their total number of benign melanocytic naevi. To investigate the possibility that numbers of naevi may have an inherited basis, naevi were examined in 23 monozygotic and 22 dizygotic twin pairs. A strong correlation in total numbers of naevi 3 mm or more in diameter was observed between MZ twins (intraclass correlation 0.83), but there was no significant correlation between DZ twins (correlation -0.24). There was no increased concordance in presence of naevi 5 mm or more over that expected by chance, for MZ or DZ twins. The results suggest a strong inherited basis for total naevus count and hence melanoma risk, perhaps involving a number of interacting genes.

Malignant melanoma risk by nativity, place of residence at diagnosis, and age at migration

Although geographic latitude is clearly linked to the risk of cutaneous malignant melanoma, the chronology of this link is unclear. Based on the 4,611 cases of melanoma with known place of nativity diagnosed in 1972-82 among the non-Latino White residents of Los Angeles County (California, United States) of known place of origin, migrants to Los Angeles from higher US latitudes enjoy relative safety from skin melanoma. This relative safety is largely unaffected by the interval since migration, even after decades of residence in Los Angeles. The same relative protection is enjoyed by native residents of more northerly US communities in comparison with co-resident migrants from the southwestern US. While the observed effect of latitude is consistent with the accepted importance of solar radiation as a determinant of melanoma risk, it suggests that early, rather than late or cumulative, exposure is of most importance. This finding does not affirm the belief that protection of adult skin from exposure to the sun will reduce the risk from melanoma. It does suggest that decades must pass before it will be possible to assess the impact on melanoma risk of any increase in ultraviolet radiation delivered to the earth as a result of the destruction of atmospheric ozone.

Melanocytic naevi: clinical features and correlation with the phenotype in healthy young males in Italy

Six-hundred and fifteen young healthy Italian males were examined for the number, localization and clinical features of melanocytic naevi. The data were correlated with the phenotype and skin type of the subjects. Eighty-eight per cent had melanocytic naevi, 7% congenital naevi and 21.3% atypical naevi with a diameter greater than 5 mm and indistinct or irregular borders and were variable in colour. Of the sample only 2.43% had more than 30 naevi. Those subjects with blond or red hair, fair skin, blue or green eyes and with a skin type of I and II had higher numbers of naevi which were more often atypical than those subjects with dark hair, brown eyes and who were skin types III-V.

Correlation of clinical and histopathologic features in clinically atypical melanocytic nevi

To define better the evolving entity of dysplastic melanocytic nevus (DMN), studies correlating clinical with histologic features of DMN are essential. However, based on a literature search, no previous quantitative analysis was found of the relationship between gross morphologic features and histologic features of DMN. The authors correlated individual clinical features with histopathologic features and histologic diagnosis of the clinically most atypical nevus in 153 melanoma patients. This nevus was identified, evaluated clinically, and removed for histologic evaluation from each patient. Gross morphologic features assessed for nevi included: size (in mm), the presence of a macular component, irregular border, ill-defined border, haphazard coloration, distortion of skin cleavage lines on tangential lighting, asymmetry, and number of colors present (12 features in all). Nineteen histologic features were assessed in each nevus by a single dermatopathologist. These included architectural, nuclear, and cytoplasmic parameters ascribed to dysplastic nevi. Each of these histologic features was correlated with the 12 individual clinical features. Seventeen percent of the nevi fulfilled the criteria for the histologic diagnosis of DMN. Among individual nevus parameters, size (in mm), irregular border, ill-defined border, macular component, and pink color were associated significantly with histologic DMN. Nevus size (in mm) and irregular borders correlated with the greatest number of individual histologic parameters. A comparison of clinicopathologic correlations for two different examiners revealed that certain clinical features are probably more important than others for the recognition of dysplastic nevi and that individual examiners have different thresholds for the perception of some gross morphologic features. These observations are relevant to the development of clinical criteria for dysplastic nevi.

Reliability of interviewer and subject assessments of nevus counts in a study of melanoma

Several types of data are presented concerning the reliability of counting or estimating the density of nevi (moles), a major risk factor for melanoma, using methods typically employed in epidemiologic studies. First, interviewer-derived counts of nevi on the arm produced estimates of inter-observer, inter-subject, temporal and random variability, and their interactions. Second, interviewer-derived arm counts and respondent self-reports of whole body nevus density were compared. Finally, we compared male and female cases and controls with respect to their reported rates of having a relative with a malignant mole. Overall, the intra-observer reliability ranged from 55 to 81%, and was better for observers with more experience. The correlation between the interviewer counts and respondents' self-reported estimates was 0.41. The data on malignant moles in relatives suggest higher reporting rates in male cases and lower reporting in male controls relative to their female counterparts, but there is little difference by sex in the reporting of one's own nevus density.

The prevalence and characteristics of congenital pigmented lesions in newborn babies in Oxford

Melanocytic naevi (MN) are recognised risk factors for malignant melanoma but the epidemiology of MN is poorly understood. Some MN are present at birth and the study of congenital lesions is an important first step toward understanding the development of MN in early life. In this study, the prevalence and characteristics of congenital pigmented lesions were documented in 1012 White caucasian newborn babies at a maternity hospital in Oxford. Only 12 babies (1.2%) were found to have pigmented skin marks and each of these had only one lesion and no other abnormalities. MN were identified with certainty in only five babies (0.5% of the population; 95% CI, 0.06%-0.93%) thus confirming the relatively low prevalence of this lesion. Four of the MN were noted to be 'small' (less than 15 mm diameter) and all five were less than or equal to 20 mm in diameter. In other respects, the MN displayed a diversity of features. Of the other lesions there were two Mongolian blue spots, one melanocytic pustule, one 'probable' MN and three unusual skin marks where the diagnosis was uncertain but considered unlikely to be MN. During the course of the study, examinations were also carried out incidentally on 39 non-White babies. Twenty-two of these were noted to have Mongolian spots (57%) and three had other pigmented lesions (8%).