I understand the gesture, but given that it was skin cancer, isn't placing the tattoo in the same exact location where the cancer had been recently excised kind of dangerous?
Being that skin cancer has a nasty habit or re-appearing, ink placed on the diseased area may cause a flareup of the nasty stuff--I hope not for his sake.
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"What is life? It is the flash of a firefly in the night. It is the breath of a buffalo in the wintertime. It is the little shadow that runs across the grass and loses itself in the sunset."
—Chief Isapwo Muksika Crowfoot's last whisper