Prove it. Since first posting, I've done a reasonable amount of scanning of breast cancer sites, and there is little or nothing about this supposed link between breast cancer and abortion. Frankly, I put this in the same "wishful thinking" category as "embryonic stem cell research" is to the pro-abortionists. It plays to the prejudices of the group involved, but is not well-supported by science.
The major problem, as I see it, with the "wishful thinking" category is that it seems to have overtaken much of the debate on a wide variety of "causes" of a wide variety of diseases.
Links between one thing and another exist for everything. In this particular case the claim is that abortion is the number one preventable cause of breast cancer...........yet others claim that smoking is the number one preventable cause of breast cancer..still others claim the number one is something else.
I'm not claiming to know if one is right, or if any of them are wrong - I'm just commenting that depending upon which study, which disease, which funding, etc., there are going to be different spins taken on the outcome of the studies.