Somatic POLE exonuclease domain mutations (hereafter simply referred to as POLE mutations) occur in sporadic tumours of the endometrium (7–15% cases) 8, 9, colorectum (1–2%) 10, 11, and, less commonly, in other cancers (although, for reasons that are unclear, somatic POLD1 exonuclease domain mutations are very uncommon). Here, POLE is linked to cancer.