" One or two cancer cells never hurt anyone. But how about a billion cancer cells? That’s how many may be in a tumor5 by the time it’s picked up by a mammogram.6 Like most tumors, breast cancer starts with just one cell, which divides to become two, four, and then eight. Every time breast cancer cells divide, the tumor can effectively double in size.7 Let’s see how many times a tiny tumor has to double to get to a billion cells. Take out a calculator. Multiply one times two. Then multiply that number by two. Keep doing that until you reach one billion. Don’t worry. It won’t take long. It’s only thirty doublings. In just thirty doublings, a single cancer cell can turn into a billion. The key to how quickly you’d be diagnosed with cancer, then, is the doubling time. How long does "

― Michael Greger , How Not to Die: Discover the Foods Scientifically Proven to Prevent and Reverse Disease