Is some breast cancer caused by free radicals from immune cells?

Yes, but indirectly. Free radicals can damage DNA but the cells have their own reparative mechanisms. For free radicals to cause cancer, the following events need to happen:-
1. Damage in individual cells significant enough to overwhelm its reparative mechanisms.
2. Damage in such a way that even if the reparative process is impaired, the cell is not allowed to commit suicide called APOPTOSIS.
3. Such a cell which fails to undergo apoptosis keeps accumulating damage enough to cause genetic mutations.
4. Sufficient number of cells achieve critical mass with the above said damage to grow into a cancer.
But the good thing is antioxidants get rid of free radicals. Every chemical and toxin in your body causes free radical damage. The carcinogenic toxins cause even more damage. Combined with high acidity and low oxygenation, you've got a prescription for cancer.
Another cause of free radical damage and thus too much cancer, is that processed foods generate more free radicals than whole foods, and have fewer nutrients to act as free radical scavengers to help protect you from those free radicals...