These changes can be caused by external factors such as environment, habits and lifestyle, or internal ones such as hormones and immunological conditions, which lead to genetic mutations in the structure of healthy cells.
Although genetic factors are determinant for the onset of cancer, cases that are due exclusively to hereditary, family and ethnic factors are not common.
Family history is one of the risks to be evaluated since the occurrence of the disease in other first degree relatives may indicate the existence of a genetic factor which increases the probability of breast cancer in the family.
However, a warning is in order: the absence of cases in the family does not mean that you or other members of your family are safe from breast cancer. Family history is only one of the other risk factors.
Besides, it is important to point out that genetic factors can make some people more susceptible to the action of cancerous agents. Other risk factors that we can mention are the behavioral and environmental ones such as: obesity/overweight; sedentary lifestyle, alcohol consumption.