Since the bumps are fluid-filled, they could be blisters from "baking" your skin. I know a lot of people consider that tanning makes them look healthy, but all tanning involves some degree of damage to the skin, leading at best to premature wrinkling, and at worst to skin cancer.
If you persist in using tanning beds, please be sure to have a full-body skin examination by a dermatologist on a yearly basis. This is especially important if you have EVER had a serious sunburn, which increases the risk for melanoma, the most serious form of skin cancer.
Best wishes...
Tanning to any great extent is NEVER a good idea but I doubt the "bumps" you and your friend have experienced have anything to do with breast cancer as this disease doesn't present in this way. I would think it might have more to do with whatever you may have used on the skin prior to your tanning session. If these "bumps" don't go away I suggest that you see either your own Dr. or a Dermatologist. I would also advise you to stop using any type of preparation on your skin and stay away from tanning until the condition has cleared. Regards ....