SGO1 and cancer: The c-AID mutations were then characterized across 49 thousand tumoral samples (9 human cohorts and 3 non-human cohorts, see Supplementary methods), revealing that: (i) they are found at a frequency of 5.2% (5.1–5.3%) in virtually all cancers (human and non-human); (ii) they show stronger activity at transcriptionally active domains; and (iii) they synergize initial non-AID hotspot mutations by a second c-AID composite mutation.