Polish Academy of Sciences researchers report on a pan-cancer atlas spanning somatic mutations in dozens of microRNA biogenesis genes. Using exome sequence data for more than 10,200 matched tumor and normal pairs, the team tallied some 3,600 somatic mutations in 29 miRNA biogenesis genes across 33 cancer types profiled for the Cancer Genome Atlas, uncovering recurrent mutations that appeared to correspond with specific cancer types and/or patient outcomes.