Tattoos are beautiful. My thoughts are that's up to your own judgment. I wouldn't get it if you have any moles in that area. Ask your doctor or a dermatologist. Tattoo ink contains carcinogens, that may increase your risk for skin cancer. But then again, so does a lot of other things. Who knows what ink they will use, and what's in it?
I don't think anyone really knows 100% for sure. I'm not a doctor, not a skin specialist, not a cancer specialist. But I am a little crazy. If it's a dream, if you're a risk taker, if you're done with your treatments, if the doctor gives you the green light, I say go for it if you're in otherwise good health. I would be more worried about choosing a well-established tattoo artist to keep it clean, and make sure you're in good health so you can handle any potential infections. I think eating sugar puff cereal every day is more dangerous. From my limited understanding, you are already at increased risk for skin cancer, because you've already had it.
If you go back for MRI scans, I did read there may be, rarely, a problem with swelling and burning in the tattoo (FDA). It says not to avoid an MRI because of this, but just tell the radiologist.
Post pictures when it's done.