No offense, but gimme a break. This sounds like the whole jelqing idea to increase the size of a man's "member". Breasts are modified sweat glands and fatty tissue (
http://en.wikipedia.org/wiki/Breast). The fact that they are fatty tissue should tell you something - ever heard of someone massaging their arms and poof - instant rock hard muscles? No, because fat doesn't transform into muscle by rubbing it, nor does it get firmer.
Think about it - if we could massage parts of our body and have it get bigger, better, more toned etc, do you really think we'd need the fitness industry? No, because people would be at home rubbing themselves to increase the size of their various body parts. Next thing ya know, someone will try selling a way of rubbing parts of your body to reduce their size...