Non-ionizing RF at high enough concentrations causes heating which can directly damage body tissue/organs. The sensitivity to this effect varies by tissue type,

Non-ionizing RF at high enough concentrations causes heating which can directly damage body tissue/organs. The sensitivity to this effect varies by tissue type, location, and most importantly by frequency. Higher frequencies are not always worse than lower ones at the same power level, molecular structure and resonances can be more sensitive at specific frequency bands. So the question with regard to tumors is can this heating cause changes in DNA? My non-scientific/non-medical opinion is that it can but not before major structural damage occurs killing the cell anyways. Even if the cell survives the DNA damage is likely to be widespread, not just a few base pairs, and the cell would destroy itself.