The most of the BRCA2 mutations occurring in our population, most probably, slightly increases the risk of breast cancer, although studies performed in New Medical Technology Center have shown that in families with aggregation of breast cancer diagnosed before the age of 50 and stomach diagnosed in men before the age of 55, the frequency of the BRCA2 gene mutation is at the level of 10–20% [27]. The gene discussed is BRCA2; the disease is breast cancer.