The interplay of sun damage and genetic risk in Australian multiple and single primary melanoma cases and controls.

BACKGROUND: Skin phenotype, host genotype and ultraviolet (UV) damage play a role in the development of melanoma. OBJECTIVES: To ascertain whether the level of UV damage at the site of melanomas was associated with genetic polymorphisms. METHODS: Deep phenotyping was performed on 1244 individuals; 281 with multiple primary melanomas (MPMs), 304 with single primary melanoma (SPM) and 659 convenience controls. Genotype data was generated using the Illumina CoreExome microarray platform, assaying over 500 000 single-nucleotide polymorphisms. A subset of variants were combined to assess a polygenic risk score (PRS) for melanoma. RESULTS: Most MPM cases were diagnosed in patients aged > 40 years, in sites with visible chronic UV damage. Women and those diagnosed at age ≤ 40 years were less likely to have perilesional UV damage. Patients with MPM had higher frequencies of MITF E318K, MC1R R-alleles and the ASIP risk haplotype. Individuals who had melanoma in a visibly UV-damaged site were more likely to carry MC1R rs75570604 [odds ratio (OR) 2·5], 9q31.2 rs10816595 (OR 1·4) and MTAP rs869329 (OR 1·4). These same alleles were more common in patients with MPM who were diagnosed at age ≤ 40 years. The mean PRS was significantly higher in MPM than in SPM and controls. Naevus count was comparable in early-onset MPM cases and those diagnosed at age > 40 years. CONCLUSIONS: Our cohort demonstrated higher frequencies of previously reported alleles associated with melanoma. MPM melanomas more commonly occur in UV-damaged areas, and these individuals are more likely to carry MC1R red hair colour alleles. Awareness of the interplay of genetic vulnerability with UV damage can stratify risk and guide recommendations for melanoma screening. What's already known about this topic? Skin phenotype, host genotype and ultraviolet (UV) damage all play a role in melanoma development. One of the main risk factors is a personal history of melanoma; second and subsequent primary melanomas account for over 20% of all melanomas registered in Queensland. Multiple loci are associated with melanoma risk, including many low-penetrance loci, which may have a cumulatively significant risk. Population-wide screening programmes for melanoma are not yet economically viable. What does this study add? Patients diagnosed with melanoma at age ≤ 40 years were more likely than older patients to have melanomas in non-UV-damaged sites. Patients with multiple melanomas had higher frequencies of MITF E318K, MC1R R-alleles, and the ASIP extended risk haplotype than patients with single melanoma. CDKN2A, MC1R and MTAP variants were more frequent in patients who developed melanomas at a younger age, but also in those whose melanomas were all on visibly UV-damaged sites. What is the translational message? Incorporating these genetic findings into the known risk factors of skin phenotype and visible UV damage may allow for a more customized and economically feasible approach to early detection of melanoma, particularly in younger patients. Plain language summary available online.

High naevus count and MC1R red hair alleles contribute synergistically to increased melanoma risk.

BACKGROUND: A high total body naevus count is the highest risk factor for melanoma; the phenotype of red hair colour, freckling and pale skin that burns easily, produced by MC1R R alleles, also predisposes to melanoma. OBJECTIVES: To determine whether the known melanoma risk factors of high naevus count and red hair or MC1R R alleles act synergistically to increase melanoma risk. METHODS: The Brisbane Naevus Morphology Study involved 1267 participants from volunteers presenting at a melanoma unit, dermatology outpatient clinic, private dermatology clinics, the Brisbane Longitudinal Twin Study and the QSkin Study. We examined pigmentation characteristics, total body naevus ≥ 5 mm count, and MC1R, ASIP and CDKN2A genotype in participants with and without a personal history of melanoma, living in Queensland, Australia, which is an area of high ultraviolet radiation. RESULTS: Cases were older than controls (median 57 vs. 33 years). Compared with individuals with dark brown hair and zero to four naevi, individuals with red hair and ≥ 20 naevi had a melanoma odds ratio of 10·0 (95% confidence interval 4·2-24·3). Individuals with MC1R R/R genotype and ≥ 20 naevi (≥ 5 mm diameter) had a melanoma odds ratio of 25·1 (95% confidence interval 8·4-82·7) compared with wild-type (WT)/WT individuals with zero to four naevi. The highest risk group is Australian men with the MC1R R/R genotype and ≥ 20 moles, who have an absolute risk of melanoma to age 75 years of 23·3%, compared with 0·8% for men with the WT/WT genotype and zero to four naevi. CONCLUSIONS: Patients who live in areas of high ultraviolet radiation, and have many large naevi and the red hair colour phenotype, particularly those with the MC1R R/R genotype, have a high risk of melanoma above the threshold recommended for screening in other cancers. Therefore, they should undergo intensive physician-led surveillance. What's already known about this topic? A high number of acquired melanocytic naevi, the red hair phenotype and MC1R R alleles all independently increase melanoma risk. Women with atypical naevi have an increasing melanoma risk gradient from darker hair to lighter hair. Women with many naevi have an increasing melanoma risk gradient from those with no elements of the red hair phenotype, to those with freckles but not red hair, to those with red hair. What does this study add? In Queensland, Australia, people with ≥ 20 naevi (≥ 5 mm diameter) and MC1R R/R genotype have a 25-fold increased melanoma risk, relative to people with zero to four naevi and the MC1R WT/WT genotype. In Queensland, individuals with ≥ 20 naevi and the MC1R R/R genotype have an absolute melanoma risk to age 75 years of 23·3% for men and 19·3% for women. This effect is independent of CDKN2A genotype. Further research is required to determine the effect of areas of lower ultraviolet radiation, as this study took place in the Queensland, Australia, which is an area of high ultraviolet radiation. MC1R R/r genotype is associated with increased total body naevus count but this is not the case for R/R. What is the translational message? Patients with many large naevi and the red hair colour phenotype, particularly those with an MC1R R/R genotype, have an unusually high risk of melanoma. In a high ultraviolet environment, this risk exceeds the threshold recommended for screening in other cancers, and such individuals should undergo intensive, regular, physician-led surveillance. Patients with many large naevi but with non-red colour hair may benefit further from clinical MC1R genotyping.

Phenotypic and genotypic analysis of amelanotic and hypomelanotic melanoma patients.

BACKGROUND: Amelanotic/hypomelanotic melanoma is associated with poorer outcomes due to a more advanced disease stage at diagnosis. OBJECTIVE: To determine phenotypic risks and genotypic associations with amelanotic/hypomelanotic melanoma to develop a clinical and genetic profile that could assist in identifying high-risk individuals. METHODS: The Brisbane Naevus Morphology Study conducted from 2009 to 2016 has recruited a core of 1254 participants. Participants were drawn from a combination of volunteers from dermatology outpatient clinics, private dermatology clinics, the Brisbane Longitudinal Twin Study and QSkin study. Case participants had a personal history of melanoma and control participants no personal history of melanoma. We specifically examined seven known candidate pigmentation and melanoma genes and pigmentary phenotypic characteristics in participants with amelanotic/hypomelanotic melanoma compared to pigmented melanomas. This assayed single nucleotide polymorphisms in MC1R, TYR, HERC/OCA2, IRF4, MTAP, PLA2G6 and MITF. RESULTS: Forty-seven participants had at least one amelanotic/hypomelanotic melanoma, and 389 had pigmented melanomas, with amelanotic/hypomelanotic melanoma patients significantly older than pigmented melanoma participants (63.3 ± 13.0 vs. 54.6 ± 15.3 years; P < 0.001). Amelanotic/hypomelanotic melanoma patients were more likely than pigmented melanoma patients to have red hair (34% vs. 15%; P = 0.01), severe hand freckling (13% vs. 5%; P = 0.01) and propensity to sunburn (63% vs. 44%; P = 0.01). MC1R R/R genotype was much more frequent in our amelanotic/hypomelanotic melanoma population (31.1% vs. 11%; P < 0.001; OR 26.4 vs. 5.9; control 1.0). Amelanotic/hypomelanotic melanoma was associated with TYR rs1126809*A/A [OR (CI 95%) 2.7 (1.1-6.8) vs. 1.2 (0.8-1.9)] and PLA2G6 rs11570734*A/A [OR (CI 95%) 3.7 (1.0-13.6) vs. 1.3 (0.9-2.0)]. The MTAP melanoma risk SNP genotype, associated with darker pigmentation, (rs4636294*A/A) was less common in amelanotic/hypomelanotic melanoma patients [OR (CI 95%) 0.8 (0.3-2.1) vs. 2.0 (1.3-3.1)]. CONCLUSIONS: Knowledge of phenotypic and genotypic associations of amelanotic/hypomelanotic melanoma can help predict risks and associations of this difficult to diagnose melanoma, which may ultimately assist clinical management and patient skin self-examination.

Iris pigmented lesions as a marker of cutaneous melanoma risk: an Australian case-control study.

BACKGROUND: Iris naevi and iris freckles have a frequency of 4% and 50% in the European population, respectively. They are associated with dysplastic naevi, but few studies have examined their link to cutaneous melanoma. OBJECTIVES: To assess whether iris pigmented lesions are a predictive indicator for cutaneous melanoma. METHODS: This is a melanoma case-control study of 1254 European-background Australians. Sun exposure and melanoma history, a saliva sample for DNA analysis and eye photographs taken with a digital camera were collected from 1117 participants. Iris images were assessed by up to four trained observers for the number of iris pigmented lesions. The data were analysed for correlations between iris pigmented lesions and melanoma history. RESULTS: Case participants over the age of 40 had similar numbers of iris pigmented lesions to age matched controls (mean 5·7 vs. 5·2, P = 0·02), but in younger case and control participants there was a greater difference (mean 3·96 vs. 2·19, P = 0·004). A logistic regression adjusted for age, sex, skin, hair and eye colour, skin freckling and naevus count found that the presence of three or more iris pigmented lesions increases the melanoma risk 1·45-fold [95% confidence interval (CI) 1·07-1·95]. HERC2/OCA2 rs12913832 and IRF4 rs12203592 influenced both eye colour and the number of iris pigmented lesions. On the HERC2/OCA2 A/A and A/G genotype background there was an increasing proportion of blue eye colour when carrying the IRF4 T allele (P = 3 × 10-4 ) and a higher number of iris pigmented lesions with the IRF4 T/T homozygote (P = 3 × 10-9 ). CONCLUSIONS: Iris pigmented lesion count provides additional predictive information for melanoma risk above that from conventional risk factors.

The BRAF and NRAS mutation prevalence in dermoscopic subtypes of acquired naevi reveals constitutive mitogen-activated protein kinase pathway activation.

BACKGROUND: Acquired naevi can have unique dermoscopic patterns that correspond to distinct microanatomical growth patterns. Previous studies on acquired naevi stratified according to dermoscopic pattern focused on the frequency of somatic BRAF mutations, whereas NRAS mutations remained to be elucidated. OBJECTIVES: To investigate the BRAF and NRAS mutation prevalence and activation of the mitogen-activated protein kinase (MAPK) pathway in distinct dermoscopic subtypes of acquired naevi. METHODS: Common mutations present in BRAF and NRAS were assessed in 40 globular, reticular and peripheral rim of globules (PG) subtypes of acquired naevi from 27 participants (19 male, 8 female; mean age 46·7 years) selected from 1261 eligible volunteers. Mutations were determined using the highly sensitive and quantitative QX200 droplet digital™ polymerase chain reaction (ddPCR) system. RESULTS: The BRAF V600E (c.1799T>A or c.1799_1800delTGinsA) and BRAF V600K mutations were detected in 85% (n = 34/40) of naevi. All BRAF wild-type naevi (15%; n = 6/40) harboured an NRAS codon 12/13 or 61 mutation. BRAF mutations were present in 92% (n = 12/13) of globular and 100% (n = 12/12) of PG naevi, whereas reticular naevi were 67% (n = 10/15) BRAF- and 33% (n = 5/15) NRAS-mutant (P = 0·037). CONCLUSIONS: We discovered that 100% of the assessed acquired naevi had either a BRAF or NRAS mutation. Using sensitive techniques capable of single-cell mutation detection, it is likely that all acquired naevi will be mutated for BRAF or NRAS. Because both of these mutations are prevalent in distinct dermoscopic naevus subsets, our study supports the role of the MAPK pathway in the development of benign melanocytic proliferations, indicating that additional genomic events besides somatic mutations in BRAF or NRAS are required for melanoma development.

Heritability of naevus patterns in an adult twin cohort from the Brisbane Twin Registry: a cross-sectional study.

BACKGROUND: Heritability of naevi counts is widely acknowledged as a potential surveillance parameter for prevention purposes. The contribution of heritability to the changes seen in naevus number and morphology over time and their corresponding dermoscopic characteristics is unknown, but is important to understand in order to account for adequate prevention measures. OBJECTIVES: To identify naevus characteristics that are strongly influenced by heritability. METHODS: This cross-sectional study included 220 individuals [76 monozygotic (MZ), 144 dizygotic (DZ)], recruited from the Brisbane Twin Naevus Study. Participants received full body imaging and dermoscopy of naevi ≥ 5 mm in diameter. Dermoscopic type, total naevus count (TNC), change in TNC with age, and naevus distribution, size, colour and profile were compared between MZ and DZ twins. Heritability of these traits was assessed via Falconer's estimate. RESULTS: Significant differences were found in comparing MZ and DZ twins for TNC, numbers of naevi 5·0-7·9 mm in diameter, counts of light-brown naevi, naevi on the back and sun-protected sites, and naevi with the 'nonspecific' dermoscopic pattern. CONCLUSIONS: This study strongly supports a heritable component to TNC, as well as changes in TNC, and the number of medium-sized naevi, light-brown naevi, specific sites and certain dermoscopic features in adults. These characteristics should be taken into account by naevus surveillance programmes and further studied to identify candidate gene associations for clinical and dermoscopic patterns in conjunction with melanoma risk stratification.