There are people who never even saw a cellphone that also get tumors. Before cellphones came out, I knew a family who had three kids all born with cancer. That may be because they lived near high-voltage lines, another source of electromagnetic radiation, and one that is present whenever you are around, not merely when you do a specific thing that most people don’t do for more than a few minutes a day.
I have seen no convincing evidence one way or the other, and what I have seen makes me lean towards no as the power levels are pretty damn low. Now, maybe if you talk like a teenage girl and keep the thing radiating next to your head seven hours a day, every day then there might be a slight risk, but truth be told, the microwave in your kitchen puts out far more radiation than your phone.
Also remember, that it is possible for a meteor to come hurtling through the atmosphere to hit you in the head and kill you. Saying it can’t happen would be lying, but worrying about it would be pointless.