"Calcium cysts" would be caused by cancer, rather than the cause of the cancer. Mammograms show the calcium, which is white on the film, and that's how we know where to biospy.
Yes, family members who have breast cancer increases risk - in other words, if we're trying to guess who may have the cancer, our guesses are more accurate in women whose mother, sister, or grandmother had breast cancer. But they do not *cause* breast cancer. The genetic and physical environment causes the breast cancer.
Smoking may be one factor that causes breast cancer.
We know that women who never have children have an increased risk of breast cancer. In med school, we learned that breast cancer used to be called the "nun's disease."