Hi,
I agree with ducky406.
I have added a site below where you'll find additional information concerning your question.
I hope you don't have breast cancer and that you'll never be afflicted with this disease.
All the best...
http://www.cancer.org/docroot/CRI/content/CRI_2_2_2X_What_causes_breast_cancer_5.asp
Cancer is extremely complicated. There is definite genetic causes known for breast cancer (BRCA 1 specifically is pretty well known, although there are others) increased your risk of getting breast cancer dramatically. But even if you have this gene that doesn't mean you will get breast cancer, which shows that environment plays a factor. However you can also get breast cancer without having this gene or any family history.
Lower your risk by a healthy lifestyle- good diet, no smoking, exercise, etc. Know your family history, because this can help determine your risk.
Also lower your risk of having something grow out of control- do monthly self exams, yearly clinical and at 40 ask for a mammogram. If you notice changes, don't ignore them. It doesn't matter if your 10 or 100, male or female, changes can be more and if you're ever in doubt its always ok to ask.