Double Heterozygosity for Rare Deleterious Variants in the BRCA1 and BRCA2 Genes in a Hungarian Patient with Breast Cancer.

Hereditary breast cancer is most commonly attributed to germline and gene variants. The vast majority of and mutation carriers are single heterozygotes, and double heterozygosity (DH) is a very rare finding. Here, we describe the case of a / double heterozygous female proband diagnosed with breast cancer. Genetic testing for hereditary breast and ovarian cancer revealed two pathogenic variants in the (c.5095C>T, p.(Arg1699Trp)) and in genes (c.658_659delGT, p.(Val220Ilefs*4)) in heterozygous form. None of the variants were founder Jewish mutations; to our knowledge, these rare deleterious variants have not been previously described in DH patients in the literature. The patient had triple-negative unilateral breast cancer at the age of 36 and 44 years. Based on family studies, the variant was maternally inherited.