Breast Cancer: Causes
In the body under the influence of various factors constantly appear abnormal cells – modified, with the wrong structure, underdeveloped (immature), etc. The immune system detects, recognizes and destroys such cells along with alien malicious micro-objects. However, even if one of the mutated cells is missed, nothing particularly terrible will happen: after a certain time and a certain number of divisions (the Heiflik limit), any living cell will die and the decay products will phagocyte very quickly to avoid inflammation. The mechanism of “programmed” at the genetic level of cell death, which must occur after a certain number of divisions (for human tissues the limit of the Heiflik is about 50 times), is called apoptosis. Every day, up to 70 billion cells die (and then are renewed at least partially) in an adult body in this way.
In a cancer cell, there is no clockwork mechanism of apoptosis. Such a cell is unable to do anything but endless division. The tissue made up of such cells is virtually immortal, it develops and grows very rapidly, becoming a macroscopic neoplasm, which we call a cancer tumor. To start such a process, a single cell with apoptosis turned off and blood lost and not destroyed by immune factors is enough. The main characteristics of cancerous (malignant) neoplasia are the absence of cytological, cellular unity or similarity with the parenchymatous tissue of the organ where such a tumor develops; the tendency to grow into surrounding tissues and structures; metastasis (the spread of cancerous cells with lymph and blood, which leads to the formation of secondary tumors-metastases in other areas of the body), rapid non-stop growth, the formation of their own blood systems (neovascularization), through which the cancerous tumor takes on a larger share of the body’s life resources.
All these properties are inherent in any form of cancer, including breast cancer.
The processes of cell renewal (regeneration) in the breast are highly intensive; this organ is richly enervated and vascularized – all of which increases the likelihood of the neoplastic process being triggered.
The mechanism and conditions of breast cancer development are thus quite clear. Another, more important and complex question is why there are many atypical cells in this area at some point, and why the immune system does not have time to destroy them (or simply does not “see”, does not recognize as a danger). The answers, usually defined as the most significant risk factors, are sought and found by modern researchers through a sophisticated multidimensional analysis of statistical data, which in turn continue to accumulate. No absolute factor or factor cluster has yet been found in the presence of which breast cancer occurs with a hundred percent frequency. It is possible that such a cause does not exist at all, i.e. the malignant process is triggered under some combination of conditions, each of which makes its own stochastic (“random”, probabilistic) contribution to the cancer risk for a given organism. Such diseases are called polyethyological or multifactorial (this is the name that has been established, although it would be more correct to call them “multifactorial”).
Breast cancer risk is significantly increased by the following factors:
- early puberty, early onset of sexual activity combined with late childbearing (above 30 years of age), avoidance or inability to breastfeed, late menopause;
- old age;
- endocrine disorders, diseases and transient imbalances (the processes of cell and tissue growth in the breast are regulated by hormones – estrogen, progestin, prolactin, etc.);
- hereditary predisposition;
- chronic diseases, primarily inflammatory ones, in the reproductive system organs;
- repeated abortions;
- substitution therapy with sex hormones for “prolongation of female youth”, and/or prolonged, for 10 years and more, taking hormonal contraceptives;
- irregular sexual life;
- mammary gland injuries and contusions (in the first year and a half or two years, the risk of starting the oncological process increases by an order of magnitude);
- radiation exposure;
- self-destructive habits (smoking, alcohol, drugs, substance abuse, etc.);
- intoxication by chemical harmful compounds;
- infections, primarily viral;
All these factors, especially exogenous (active or imported), are currently under active study to clarify their statistical significance and potential oncogeneity.