[Rich66]

http://www.nytimes.com/2009/12/29/he...ewanted=1&_r=1

...some researchers are taking a fresh look at ideas that were dismissed as folklore — a blow to the breast might spur cancer, an infection might fuel cancer cells, a weak immune system might let cancer spread. They also say the new approach may help explain mysteries, like why the breast cancer rate plummeted when women stopped taking menopausal hormones.