In 2001, my mammogram results stated that I have "... dense breast parenchyma bilaterally." According to my doctor, this translates into what he called, Fibrocysitic Disease of the Breast. Basically, the breast has a kind of lumpiness to it making mammograms a bit more difficult to read. He added that, although it is not rare for some women to have this condition, it is considered an abnormality. And, he advised me to be particularly aware of any changes, within my breasts, when I perform my self exam. In his opinion, having Fibrocystic breasts could be hereditary. I don't know if your density is a result of Fibrocystic Disease... it may not be. But, I agree with japdip... in that it's probably unlikely that the tattooing and/or the subsequent laser removal is related to your density findings.
I don't think the tatoo removal would cause the density since this was a skin surface issue. A density can be something as simple as some breast tissue that has folded over on itself and may not even be evident when the compression views are done. Follow up for sure but I wouldn't get freaked out about this just yet. Take care ...