I was about halfway through my cancer treatment for soft tissue sarcoma of the nasal cavity — a type of nasopharyngeal cancer —when I decided to get a tattoo. The tumor in my head was shrinking, and my prognosis was looking really good. I wanted to do something to memorialize the experience once I got past it.

At first, I thought I’d get a rainbow in front of a storm cloud, because in nature, you can’t really have one without the...