I responded to your other post where you asked the same question. It may be that you are producing milk. That's what happens when a baby leaves your body, your body produces milk for it.
That would probably only happen if you were pretty far along though.
Nope, it's not cancer - there is no scientific connection between abortion and breast cancer, despite what some right-wing windbags like to tell young women.
You breasts are probably tender and swollen because of fluctuations in your hormones. Abortions means a sudden drop in estrogen/progestin, and changes in the hormones usually affect the breasts. I just went on birth control pills, and my boobs are going through the exact same thing!
Unfortunately, there is not much you can do about it. You just have to let your hormones return to normal. Rest assured that it is not serious and not permanent.