WT1 and Wilms tumor: Nephrogenic rests (precursors to malignant Wilms' tumors) formed as a consequence of mono-allelic inactivation transformed into the eponymous renal malignancy upon secondary WT1 allele inactivation, a classic example of Knudson's two hit hypothesis (Ruteshouser et al., 2008; Royer-Pokora et al., 2010; Kaneko et al., 2015).