Tumor cells encode the same genes as non-tumor cells. The difference is more likely to be in the expression level or epigenetic (de)repression of a particular

Tumor cells encode the same genes as non-tumor cells. The difference is more likely to be in the expression level or epigenetic (de)repression of a particular gene than the presence or absence of that gene. Organisms don't tend to keep around genes that only serve to form tumors. A slightly better approach would be to use RNA-sequencing to look for mRNA signatures in tumor vs normal cells.