Genetics and breast cancer

Breast cancer, occurs when cells in the breasts begin to multiply uncontrollably, resulting in the formation of tumors. If left untreated, the cancerous cells can spread throughout the body and become deadly. This type of cancer is a global health concern, affecting people of all ages and genders.

Early detection is essential in the fight against breast cancer, as the earlier it is detected, the greater the chances of successful treatment. Despite advances in medicine, breast cancer remains one of the leading causes of cancer deaths worldwide.

In 2020, an estimated 2.3 million new cases of this type of cancer were diagnosed worldwide. This disease does not discriminate, affecting both men and women. However, women have a significantly higher risk of developing breast cancer in their lifetime.

In this blog, we will explain this form cancer cancer in detail: from its risk factors, the influence of genetics and detection methods.

Populations with a greater predisposition to breast cancer

Among women from developing countries, breast cancer continues to be the main cause of death (3). On the other hand, the incidence varies greatly among ethnic groups (4), for example, in Ashkenazi Jews the disease is more prevalent due to the high degree of consanguinity present in this population group.


Breast cancer risk factors

  • Aging: The risk of breast cancer increases with age, being more common in women over 40 years old.
  • Obesity: Overweight, obesity and a sedentary lifestyle are associated with an increased risk of developing breast cancer.
  • Excessive alcohol consumption has been associated with this type of cancer.
  • Family History of Cancer: Having close relatives with a history of breast cancer may increase the risk.
  • Radiation Exposure: A history of radiation exposure.
  • Reproductive History: Factors such as age of onset of menstrual periods and age at first pregnancy may influence risk.
  • Smoking: Tobacco smoking has been linked as a risk factor.
  • Post-Menopausal Hormone Treatment: Prolonged use of hormone replacement therapy after menopause may increase risk.


Mamografia cancer de mama y genética - breast cancer and genetics


Breast cancer in men

Although is commonly associated with women, it is important to note that it can also affect men, although it is much less frequent, especially in those over 60 years of age. This is because, compared to women, men have less developed breast tissue, which means there are fewer glandular cells where a malignant tumor could develop. Consequently, the incidence of breast cancer in men is less than 5%.


Clasificación y Oncogenes

An oncogene is an abnormal or activated gene that comes from the mutation of an allele of a normal gene called a proto-oncogene. Oncogenes are responsible for the transformation of a normal cell into a malignant cell that will develop a certain type of cancer.

In breast cancer we find different types depending on the absence or presence of estrogen/progesterone receptors (5):

  • Hormone receptor positive/ERBB2 negative
  • ERBB2 positive
  • Triple negative (tumors lacking the 3 standard molecular markers).

Regarding oncogenes, one of the most important is HER2, associated with breast cancer. Precisely for this reason, its progression is studied and analyzed both in terms of survival and potential recurrence (6), i.e., the possibility that the tumor may recur.


Evolution and approach to the disease

The evolution of this type of cancer is usually silent, so most diagnoses are made in routine medical examinations. Occasionally, patients present with a lump in the nearby area or in the breast itself (2).

If we look at the history, a positive fact is that the mortality rate has been decreasing steadily for the last thirty years (7). It has also been shown that many breast cancers are non-metastatic at the time of diagnosis (5). In turn, some research suggests that not all cells within this form of cancer have the capacity to develop tumors (8).

If we return to the classification and take, for example, the triple negative type, we can affirm that it is the most likely to recur, although, on the other hand, it has a high survival rate with respect to the other types. In either case, it is essential to identify and know in depth the patterns manifested by each of these typologies. In this way, clinical strategies will be able to have an increasingly personalized approach in order to be able to establish increasingly effective treatments.



It must be taken into account that there are different types of breast cancer, so the treatments will not always be the same. Currently, surgery, radiotherapy, chemotherapy, hormone therapy, targeted therapy and immunotherapy are used (9).

The most common treatment is with cyclophosphamides, but in addition to these, according to recent research, we find trastuzumab which, as an adjunct to chemotherapy, is offering good survival results (10). However, the analysis of gene expression in breast cancer has so far not made it possible to establish therapeutic strategies adapted to each individual (11).

Furthermore, it is important to emphasize the need to choose the right treatment, since in some cases side effects can occur (9) (10).


Cancer de mama y genetica mujer en tratamiento de cancer - Breast cancer


Detection, diagnosis and prevention

In genetics, breast cancer cannot be understood without speaking of genomic instability, an essential concept in the understanding of its development (12). Genomic instability is the increased tendency to present genetic mutations or other genetic changes that appear during cell division and is usually associated with many types of cancer.

Among the most important genetic tools we have found, two are particularly noteworthy:

MicroRNAs, which are diagnostic biomarkers. For example, miR-99a-5p (13) has recently been discovered in breast cancer and has been identified as a good tool for the early detection of breast cancer.
Genetic tests, which can be preventive (when they analyze part of the genes involved in a pathology) or diagnostic (when they analyze all the DNA that affects the pathology).

24Genetics genetic tests (used as preventive tests) allow more informed decisions to be made that help people improve their well-being. Specifically, our Health test covers the genes BARD1, BRCA1, BRCA2, BRIP1, PALB2, PTEN, TP53, CHEK2, CDH1 and ATM, which are directly related to breast cancer (14).

Hereditary breast cancer accounts for about 10% of all cases of this cancer, which means that there are genes with mutations related to this type of malignant tumor. Specifically, people with a mutation in the BRCA1 or BRCA2 genes have an increased risk of breast and even ovarian cancer (9).

At 24Genetics, we try to raise awareness of the importance of having a genetic test, as it can help many people to identify whether they have genes associated with this type of cancer in their genetics, especially if there is a family history of this pathology.


  1. World Health Organization. 2021.
  2. Torre, L.A., et al. (2015). Global cancer statistics, 2012. CA: A Cancer Journal for Clinicians, 65.
  3. Momenimovahed, Z., & Salehiniya, H. (2019). Epidemiological characteristics of and risk factors for breast cancer in the world. Breast Cancer: Targets and Therapy, 11, 151 – 164.
  4. Waks, A.G., & Winer, E. (2019). Breast Cancer Treatment: A Review. JAMA, 321, 288–300.
  5. Slamon, D., et al. (1989). Studies of the HER-2/neu proto-oncogene in human breast and ovarian cancer. Science, 244 4905, 707-12 .
  6. DeSantis, C., et al. (2019). Breast cancer statistics, 2019. CA: A Cancer Journal for Clinicians, 69.
  7. Veer, L.J., et al. (2002). Gene expression profiling predicts clinical outcome of breast cancer. Nature, 415, 530-536.
  8. Al-Hajj, M., et al.(2003). Prospective identification of tumorigenic breast cancer cells. Proceedings of the National Academy of Sciences of the United States of America, 100, 3983 – 3988.
  9. Slamon, D., et al. (2001). Use of chemotherapy plus a monoclonal antibody against HER2 for metastatic breast cancer that overexpresses HER2. The New England journal of medicine, 344 11, 783-92
  10. Yeow, Z.Y., et al. Targeting TRIM37-driven centrosome dysfunction in 17q23-amplified breast cancer. Nature 585, 447–452 (2020).
  11. ACS Sens. 2021, 6, 3, 1022–1029. February 18, 2021.
  12. Health report. (2021). 24Genetics

Written by Debora Pino García


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