TET2 and cyclic hematopoiesis: To assess which immune cells harbored CHIP mutations in TI-CH, we performed single-cell genotyping29 on the tumor immune infiltrate from two TRACERx patients with TI-CH that were not part of the discovery cohort (Fig 1F and Fig S12A–B): CRUK1214, harboring mutations in TET2 (VAF of 43% in blood and 26% in tumor) and SRSF2 (VAF of 43% in blood and 20% in tumor), and CRUK1358, with a single TET2 mutation (VAF of 12% in blood and up to 3% in tumor).