IGF2 and Wilms tumor: BWSp patients with nephroblastoma that show loss of imprinting (LOI) at 11p15, affecting IGF2 and H19 either by GOM at the IC1 or upd(11)pat, have a high frequency (17.3%) of bilateral tumors [39], suggesting that the overexpression of IGF2 is causative for the nephrogenic rests.