If we only knew what those "causes" were .... I suppose fate is as good an answer as anything else until proven otherwise. It's my understanding that a greater number do occur on the left. I've heard theories about that one but nothing has been proven as far as I know.
Hi Bio_as,
If I understand your question, I think you are asking how cancer ends up in the left breast, right breast or both. I can only give you my opinion, but as a breast cancer survivor I had cancer in both breasts and I believe what cancer ended up in what breast was fate. I know I have a hereditary component (I'm positive for BRCA2), but as to where it occurs, I think it's fate or chance.
Chris
Healingwell62
Breast Cancer Community Leader