Interestingly, JAK2 and STAT3 were identified as significantly mutated in the metastasis/relapse screen even though they had not been discovered in the earlier (and larger) exome studies of primary breast cancers (Banerji et al., 2012, Cancer Genome Atlas Network, 2012, Ellis et al., 2012, Shah et al., 2012, Stephens et al., 2012). This evidence concerns the gene JAK2 and breast cancer.