Germline Cancer Susceptibility in Individuals with Melanoma.

BACKGROUND: Prior studies have estimated a small number of individuals with melanoma (2-2.5%) have germline cancer predisposition, yet a recent twin study suggested melanoma has the highest hereditability among cancers.

OBJECTIVE: To determine the incidence of hereditary melanoma and characterize the spectrum of cancer predisposition genes that may increase the risk of melanoma.

METHODS: 400 individuals with melanoma and personal or family history of cancers underwent germline testing of >80 cancer predisposition genes. Comparative analysis of germline data was performed on 3 additional oncologic and dermatologic datasets.

RESULTS: Germline pathogenic/likely pathogenic (P/LP) variants were identified in 15.3% (61) individuals with melanoma. Most variants (41, 67%) involved genes considered unrelated to melanoma (BLM, BRIP1, CHEK2, MLH1, MSH2, PMS2, RAD51C). A third (20, 33%) were in genes previously associated with familial melanoma (BAP1, BRCA2, CDKN2A, MITF, TP53). Nearly half (30, 46.9%) of P/LP variants were in HRD genes. Validation cohorts demonstrated P/LP rates of 10.6% from an unselected oncologic cohort, 15.8% from a selected commercial testing cohort and 14.5% from a highly selected dermatologic study.

LIMITATIONS: Cohorts with varying degrees of selection, some retrospective.

CONCLUSION: Germline predisposition in individuals with melanoma is common, with clinically actionable findings diagnosed in 10.6% to 15.8%.