While a tremendous amount of research has been done on the causes of breast cancer, an exact breakdown by percentages or some such measure is still not completely accurate. Hormone levels and those levels related to age are factors. Diet and heredity are also among the most important indicators of breast cancer probability.
The hormones in question are estrogen and progesterone. Any levels significantly different from the average of the females at the age the woman is, represents an increase in probability of getting breast cancer. This includes age factors for the beginning age of menstruation as well as the ending age. If a girl begins menstruation at an early age, or a woman past middle age has not reached menopause, cancer risk increases.
Because of this connection, hormone therapy after menopause is not always a recommended practice – especially if there are is a family history with links to breast cancer.
The dietary aspect is also under scrutiny, but all indicators are that obesity and/or a diet that is high in percentage of calories consumed as fat are both positively linked to higher breast cancer probability. There are also indications that excessive alcohol usage is a prominent factor.
Whether breast cancer is genetic is really two questions. One is whether family genetics are a major factor, and the other is the genetic cause of recurrence in the actual patient. Concerning the latter, a woman who previously had breast cancer that was successfully removed still has a very significantly higher risk of getting it again. An operationally removed tumor in early stages represents the best chance of reducing future risk. Chemotherapy and radiation are not as effective, since the cancerous stem cells are never destroyed. Stem cells are the special cells that do the multiplying and replacement of old cells. So if cancerous stem cells, even in small quantities are still present, their genetic code will be replicated in some of the cells with which the body replaces old cells.
Family genetic factors are definitely involved, although most researchers believe that genetic inheritance is not the primary cause of cancer. It’s a matter of risk, but a small enough percentage of the population carries the faulty gene code that causes the disease. It is now believed that about 5 to 10% of breast cancers are caused by inherited genetic mutations. There is definitely an increased risk for an individual whose mother or sister has gotten breast cancer, especially if this has occurred at an early age (before menopause).
Researches have identified two particular genes that are direct causes of breast cancer. Also, the presence of oncogenes (a general cancer causing mutation) can result in the development of breast cancer, as well as every other form of cancer that can afflict us.