Indeed the possibility that IGF1R is not a tumor-specific target, but just a stage-specific differentiation marker of interstitial cell of Cajal (ICC) precursors cannot be ruled out, since a recent work by Lorincz and colleagues showed that ICC precursors are a rare IGF1R-positive, Kit(low), CD44(+), CD34(+), Insr(+) cell population, retained in postnatal life, that is dependent on IGF signaling for survival and differentiation [53]. The gene discussed is CD44; the disease is intrahepatic cholangiocarcinoma.