Cancer is the name given to all malignant tumors, the main reason for which is uncontrolled growth, and the tumor, which has become a mass as a result of uncontrolled cell proliferation, also attacks the surrounding cells and envelops the whole body (metastasis) in the later stages of the disease. Although cancer is an important health problem, it is not a common disease in childhood. On the other hand, statistics show that cancer affects one in three adults, causes up to 20% of all deaths, and covers about 10% of treatment costs in developed countries. Although it is known that cancer develops under the influence of genetic and environmental factors, environmental factors are more prominent in the formation of some types of cancer. Breast cancer is one of the cancer types known to have tumor suppressor genes in its etiology. These tumor suppressor genes are BRCA1 and BRCA2 genes. Studies have shown that these two genes are particularly effective in the development of familial breast cancers. These types of cancers occur much earlier than non-familial cancers. The research, two genes; It has shown that it is especially effective in the development of familial breast cancers.