Our choice of the four BRCA1 mutations: 5382insC (c.5266dupC), 300T>G (p.181T>G), 185delAG (c.68_69delAG), and 3819del5 (c.3700_3704del5) analysed in the present study reflects their high prevalence among Polish breast and/or ovarian cancer families and is based on the results of previous research [5]. Here, BRCA1 is linked to ovarian cancer.