In this article, we delineate a loosely selected cohort comprising patients with a history of early-onset breast cancer and/or a familial occurrence of cancer. The aim of this study was to gain insights into the presence of breast cancer-related gene variants in a population from a micro-region in southern Brazil, specifically the Metropolitan Region of Curitiba. This area exhibits a highly genetically mixed population, mirroring the general characteristics of the Brazilian people. Comprehensive next-generation sequencing (NGS) multigene panel testing was conducted, involving the evaluation of twelve patients. Two pathogenic variants and one candidate pathogenic variant were identified: BRCA2:c.8878C>T, p.Gln2960Ter; CHEK2:c.1100delAG>A, p.Thr367Metfs*15 and BRCA2:c.3482dupG>GA, p.Asp1161Glufs*3, a novel variant, previously unpublished, is reported.