Breast cancer and ovarian cancer are among the most common cancers in women. Molecular biological and genetic changes in tumor cells are studied in detail. This is relevant both to the treatment and the creation of new promising molecules and approved drugs, and to the identification of mutated genes, the carrier of which will place healthy women in the group of high-risk for the development of malignant diseases. BRCA1 and BRCA2 are tumor suppressor genes. When functioning normally, they encode enzymes that repair mutations and errors in DNA organization. Mutations in BRCA1/2 inactivate genes, leading to the accumulation of genetic damage and malignant degeneration of cells. Between 5% and 10% of all breast cancers are due to inherited and/or acquired mutations in BRCA 1/2. The same genetic changes are also responsible for about 15% of ovarian cancers. Sometimes, in BRCA 1/2 mutation carriers, both cancers develop simultaneously or sequentially over time. Among male carriers, statistics show a higher incidence of prostate carcinoma and pancreatic cancer. Given the high oncological risk and the hereditary transmission of mutations, the study of the genetic status of patients with the above localizations and with a prophylactic purpose of their healthy female relatives is justified in the following cases: Cancer of both breasts of a woman (bilateral); Breast cancer diagnosed before age 45; Two metachronous tumors – of the breast and of the ovaries in the same patient; Cases of breast cancer among men in the family; Multicentric breast cancer (with multiple tumor foci in the affected mammary gland); Family history of oncological diseases. In these cases, genetic counseling and testing of the cancer patient for BRCA1/2 mutations is recommended. In the presence of such, healthy female relatives are informed about the genetic transmission of the mutated genes and, in the context of genetic counseling, are informed about the risks of developing breast and ovarian cancer in them. Assessment of the risk of developing malignant diseases of the mammary glands and ovaries based on statistical data (Journal of Clinical Oncology, 2007). Risk of development without BRCA mutations Risk of development with BRCA 1 mutations Development risk with BRCA 2 mutations Breast cancer 12% 55-65% 39% Ovarian, fallopian tube and peritoneal cancer 1.5% 30-60% 15-25% Evidence of BRCA 1/2 mutations in healthy relatives of oncological patients requires a focus by medical professionals on specific regular examinations from a young age (30-35 years of age) for screening and early diagnosis of breast cancer and ovarian cancer. In the process of follow-up of healthy carriers of BRCA 1/2 mutations, mammography and MRI of both mammary glands are performed once a year (examinations should be at an interval of 6 months between them),physical examinations by a specialist, dynamic monitoring of a tumor marker – CA 15-3. NEWS_MORE_BOX Regarding ovarian cancer, screening is carried out through periodic examinations and tests – transvaginal ultrasound, physical examinations and monitoring of the tumor marker CA 125. However, these measures have not proven effective in reducing mortality from ovarian cancer among carriers of BRCA mutations . The most effective and practiced prophylactic option for BRCA 1/2 carriers is surgical radical removal of the ovaries, fallopian tubes and breasts (bilateral salpingo-oophorectomy, bilateral mastectomy). In this way, the tissues in which and from which cancer can potentially develop are removed. Radical removal of the ovaries and tubes reduces by 80% the risk of developing an oncological disease from these organs (it is not 100%, because in some cases such a disease already exists, but has not been diagnosed). A higher risk remains for peritoneal carcinoma, which histologically resembles ovarian serous adenocarcinoma. The operation also halves the oncological risk for hormone-sensitive breast cancer due to the lower production of estrogens after oophorectomy. There are different techniques for bilateral mastectomy in women. No matter how radical the surgeon is, it is always possible for glandular tissue from the mammary glands to remain in the chest wall, from which cancer could subsequently develop. Risk reduction after surgery averages about 90%, but never 100%. Further dynamic follow-up of these healthy women is necessary.Risk reduction after surgery averages about 90%, but never 100%. Further dynamic follow-up of these healthy women is necessary.Risk reduction after surgery averages about 90%, but never 100%. Further dynamic follow-up of these healthy women is necessary.