“What she and others discovered begins to explain why things like smoking or coal mining or sunbathing are so carcinogenic. Each activity injures the tissue and damages the DNA. When the tissue is damaged, the immune system kicks in and cleanses the site and helps stimulate new tissue growth. The trouble is that when the DNA is damaged, the new cells that grow can be malignant cells, some that are made up of self but that are different enough to behave like a cancer.”