It is never a good idea to have a tattoo placed too close to or over an existing mole to create a beauty mark. Any changes that can occur in a mole — symmetry, border, color, size, shape, texture — are potential warning signs that the lesion may be evolving into a melanoma or another skin cancer. Melanomas that are discovered and removed at an early stage are almost always completely curable, but more advanced melanomas are far harder to cure. This is especially important for people who have multiple moles or atypical moles (dysplastic nevus syndrome), since they are at increased risk of developing melanoma, potentially within one of their moles.
When getting any tattoo or permanent makeup, it’s best to leave all moles completely visible, because anything that could delay detection can be extremely dangerous.