Abstract 5050: Germline variants in CDKN2A wild-type melanoma prone families

Abstract The presence of germline pathogenic variants in CDKN2A is a well-established underlying cause of familial malignant melanoma. While pathogenic variants in several other genes have also been linked to melanoma development, many familial cases remain unexplained. We analyzed for pathogenic germline variants in a panel of 360 cancer related genes in a set of 56 Norwegian melanoma prone families. The index cases and families were selected based on familial history of melanoma and/or multiple primary melanomas in the same individual, along with previous negative tests for pathogenic CDKN2A variants. We found 6 out of 56 index individuals to carry germline pathogenic or likely pathogenic variants. These variants were found in BRCA2, MRE11, ATM, MSH2, CHEK2 and AR. In addition, one family member with a melanoma diagnosis (not index case) carried a pathogenic variant in MAP3K6. In genes typically linked to xeroderma pigmentosum, we found a high fraction of variants previously considered benign and/or as variants of uncertain significance. In particular the XPCL48F variant was found in 8 out of 56 indexes, thus, the allele fraction (0. 07) was significantly higher than in comparable healthy populations (p-values from 0. 007 to 0. 014). Similarly, we found presumed benign or uncertain variants in MC1R to be significantly enriched or numerically higher in index cases versus comparable healthy populations (p-values from 0. 009 to 0. 1). The common MC1RArg151Cys variant was highly enriched in our cohort (p=0. 001). In conclusion, we found that several melanoma prone families harbored pathogenic variants in genes not usually linked to melanoma. Citation Format: Stian Knappskog, Gjertrud T. Iversen, Marie Loeng, Amalie L. Holth, Per E. Lonning, Jurgen Geisler. Germline variants in CDKN2A wild-type melanoma prone families abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 5050.