Rest assured that whether you have a paper cut or a softball-sized mass visibly growing on the side of your head, some web site, some blog, somebody, somewhere on the Internet will confirm that your symptom could be a sure sign of some fatal malady. When I was first diagnosed, I surfed around a bit and decided that I'd limit my information gathering to sites and people who I fully trusted.
So what the hell is Tumor Lysis Syndrome? Let's Google it. I didn't have to get beyond the descriptions on the results page to encounter this: "Tumor Lysis Syndrome is a life-threatening oncologic emergency."