there are different kinds of gyno...in layman's terms, the puberty gyno is simple activated breast tissue related to high levels of estrogen during adolensence, it should run from the nipple laterally. Hard lumps is another kind of tissue that has been activated. The tissue is lymph tissue, everyone has it, but w/o levels of estrogen (and more specifically ratios of estrogen/test/progesterone) it stays relatively dormant. It will NOT go away w/ dieting, but there is probably not as much as you think there is. I have it; but when i got to sub 6% bf, it was hardly noticable, back around 10-12ish, it bothers me.
My philosophy: if it will make a positive lifestyle influence and make you feel better about yourself and live a normal life ( like not tryin to remain at sub 6% bodyfat ) consider surgery. I am 21 and it has always been a concern of mine, but i notice it; while many others do not. I figure someday, i'll have the money and get it removed just like The Rock lol