Tamoxifen should not prevent you from having a tattoo removed. It's always best though, to mention to the person who is doing the removal , what drugs or treatment you may be having , or have had, if you feel comfortable with that.
If you have had breast surgery and radiotherapy though and your tattoo is around the breast area, then these treatments may affect the tattooed skin, potentially taking a bit longer to heal and to get a good cosmetic result. You can always check with the breast care nurse even if you had your treatment a few years back, to make sure for your peace of mind, as they will have all your medical details.
