Our clinical genetic testing, in particular, benefits from the presence of five of the most common mutations of BRCA1 (c.181T>G, c.4035del, c.5266dup, c.3700_3704del, c.68_69del and c.5251C>T), which constitute about 77% of all BRCA1/2 mutations detected in Polish women with breast cancer [26]. This evidence concerns the gene BRCA1 and breast cancer.