  All this would be challenging enough as it is, but there is a yet further challenge to cancer classification. Cancers arising in the same tissue or organ can be more genetically dissimilar than cancers arising in different tissues or organs. Or, “cell-of-origin influences, but does not fully determine, tumor classification” (Hoadley, et al. 2014, 2018). Genomic information, far from providing a way to sort all cancers into a Linnean hierarchy, instead yields what philosophers have called cross-cutting classifications (Khalidi, 1998). One might think genetic profile should trump tissue or cell of origin for purposes of classification. But it turns out that where a cancer arises in the body is rather important to know. Characteristics of the tissues and organs in which a cancer arises shape the course of disease in a complex fashion (Öhlund, et al. 2017; Fessler, et al. 2016).  Moreover, the rise of epigenomics, proteomics, and transcriptomics, and “regulomics” generates further challenges with classification, suggesting genomic information needs to be supplemented. For instance, it turns out changes in microRNA in cancer cells—non-coding RNA, which affects the expression of genes—can affect cancer initiation, progression, and responses to drugs (Hrovatin, et al. 2018). This is just one of several “extra-genomic” factors that play an important role in cancer causation and thus, presumably, ought to play at least a partial role in informing cancer taxonomy.