Nevus count and dermoscopic pattern associated with MC1R RHC-variant alleles in a case-control study of melanoma

Proceedings: AACR 106th Annual Meeting 2015; April 18-22, 2015; Philadelphia, PA The total number of acquired melanocytic nevi (TNC) is the strongest known risk factor for cutaneous malignant melanoma (CMM). An increased risk of CMM is also seen with individuals with red hair, fair skin and poor tanning ability (RHC phenotype); and who carry variant alleles of the MC1R gene designated as R. High freckling scores but reduced nevus counts have been reported in individuals with the RHC phenotype. The relationship between these reciprocal phenotypes of lower vs higher nevus counts, both with increased risk of CMM, is complex and supports hypotheses of different pathways to melanoma formation. We have reported on a case-control study of nevi in volunteers from the South-east Queensland area combining an assessment of pigmentation characteristics, nevus phenotype including dermoscopic nevus subtypes with genotypic comparisons and melanoma risk for 573 individuals. This sample set has been further examined to delineate the nevus characteristics of 46 individuals who are homozygous MC1R RHC allele carriers R/R. We wished to determine if there is any commonality in the pigmentation or melanocytic nevus phenotype including number, size, distribution, profile and colour that may distinguish these patients. Body mass index (BMI), body surface area (BSA), TNC and MC1R genotype were analysed and found that participants with personal melanoma history had higher TNC (P<0.005). We found no association between MC1R genotype and BMI but there exists a weak association between BSA and higher TNC. Within the MC1R R/R cohort, melanoma patients are more likely to have high TNC than controls (P<0.01). The signature dermoscopic pattern for the individuals in the MC1R R/R group is at increased odds of being a non-specific pattern (P<0.01). A significant difference in MC1R R/R TNC dependent on melanoma history exists and there is a predisposition towards a non-specific signature nevus pattern. Citation Format: Phil McClenahan, Kasturee Jagirdar, Katie Lee, Elizabeth McEniery, Sam Beh, Brian Burke, David L. Duffy, H. Peter Soyer, Richard A. Sturm. Nevus count and dermoscopic pattern associated with MC1R RHC-variant alleles in a case-control study of melanoma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5588. doi:10.1158/1538-7445.AM2015-5588