What if we told you that you have cancer cells? You'd probably get pretty upset and angry at the authors of that headline😁. But in fact, cancer cells are in all of us - they appear in every living organism. It happens as a result of a DNA coding error inside a healthy cell. And mistakes happen from time to time. Why don't these cancer cells always develop cancer? Because our immune system stands guard and prevents the growth of cancer cells by eliminating these "embryos". Special killer T-cells do this.