Unlike mature ICCs, the KITlowCD44+CD34+ stem cells are resistant to KIT inhibition, even in the presence of an activating KIT mutation.31 The high IGF1R expression in the ICC progenitors suggests that these may be the cells of origin of wild-type SDH-deficient, IGF1Rhigh GISTs. The gene discussed is IGF1R; the disease is intrahepatic cholangiocarcinoma.