CTNNB1 and granular cell tumor: The loss of the PI3K/AKT signaling antagonist gene Pten in GC rarely causes GCT, but concomitant activation of CTNNB1 and loss of Pten in the Ctnnb1tm1Mmt/+;Ptentm1Hwu/tm1Hwu;Amhr2tm3(cre)Bhr/+ (CPA) model results in the development of aggressive, metastatic GCT with 100% penetrance [7].