Trauma to the breast, such as a hit or a bruise, can cause a malignant tumor. Cancer develops over a long period of time, and the bruise may just make the woman aware of what was already there. Benign breast cysts are a precursor to cancer. More than 90 percent of all women have benign breast cysts that fluctuate in size with their hormonal cycle. Large benign cysts often do need to be removed or drained, however, as their presence can mask a small tumor.
Caffeine causes cancer.
There is no proof that by itself caffeine can cause breast cancer. But it does have a relation to cyst development. At one point it was speculated that large-breasted women may have a higher incidence of breast cancer, but breast size has not been proven to be an absolute cause. What has been shown to be a risk factor is being overweight. Heavy exercise, such as running, can lead to breast cancer.