The fact that KLF3 mutations in EEC occur predominantly at homopolymer tracts, were restricted to the MSI-hypermutated EEC subgroup, and are more frequently mutated in late-stage than early-stage MSI-hypermutated tumors (25.9% versus 11.4%, respectively), indicate that KLF3 is an MSI target gene that may be involved in the etiology and progression of a subset of hypermutated EECs. The gene discussed is KLF3; the disease is exstrophy-epispadias complex.