Despite an abundance of over-simplified media messages about “the war on cancer,” the scientists in the trenches of that so-called war know that cancer is anything but homogeneous. Not only is a disease like breast cancer far more than one homogeneous disease, but even within one patient’s tumor, there may be a vast diversity of cell types, giving rise to a vast diversity of genetic mutations. This cell heterogeneity has everything to do with why some medications work on some tumor cells while other tumor cells survive and give rise to new drug-resistant cells. It’s ecology, natural selection, and survival of the fittest in the ecosystems of human cancers. “Every cell in a tumor could theoretically be different,” says oncologist Charles Swanton of the Lond Research Institute. “If you take a metastatic tumor with millions of cells and assume that every cell is different, you’re starting to get a sense of the enormity of this challenge.” Read more here about how scientists are contemplating tumor cell heterogeneity as a means of predicting which tumors are more likely to respond to specific drug treatments and which tumors have a higher likelihood of spreading.