Stochastic (Replicative) Factors Versus Environmental and Inherited Factors: R-tumor Versus D-tumor Classification. The adjusted ERS (aERS) is indicated next to the name of each cancer type. R-tumors (green) have negative aERS and appear to be mainly due to stochastic effects associated with DNA replication of the tissues’ stem cells, whereas D-tumors (blue) have positive aERS. Importantly, although the aERS was calculated without any knowledge of the influence of environmental or inherited factors, tumors with high aERS proved to be precisely those known to be associated with these factors. From Tomasetti C, Vogelstein B. Cancer etiology: Variation in cancer risk among tissues can be explained by the number of stem cell divisions. Science. 2015;347:78-81.Abbreviations: FAP = Familial Adenomatous Polyposis; HCV = Hepatitis C virus; HPV = Human papillomavirus; CLL = Chronic lymphocytic leukemia; AML = Acute myeloid leukemiaReprinted with permission from AAAS.