In the Baltic region, previous research by several groups has demonstrated that two germline PVs in the BRCA1 gene—c.4035del and c.5266dup—are founder variants in these populations and account for approximately 80% of all identified PVs in the BRCA1 gene in BC and OC patients [4,8,9,10,11]. This evidence concerns the gene BRCA1 and breast cancer.