Breast cancer and genetics.

Familiar aggregation of breast cancer has been known since Roman times, but it has been discussed in practical terms only from the 19th century. Most of the studies dealing with this issue suggest that the risk is higher in relatives of patients with early onset and that the risk also increases as a function of the bilaterality of the disease or the simultaneous presence of breast cancer and ovarian cancer.A series of epidemiological studies consistently suggest hereditary autosomal dominant transmission with reduced penetrance. Previous epidemiological research and collection of data from families has been used only from the 1990s in order to identify disease genes. The BRCA1 gene was identified as the first gene responsible for hereditary forms of breast cancer and subsequently BRCA2. In 1995 both genes were identified and cloned, and they demonstrated to have only minimal homology. The conclusions deal with genetic counseling and the evaluation of the risk of developing cancer.