PTEN and neoplasm: Originally identified as the mouse ortholog of human PTEN/MMAC1 (Steck et al. 1997), mouse Pten encodes a phosphatase with tumor suppressing activity mediated by its role as a phosphatidylinositol 3 kinase (PI3K) signaling antagonist (Stambolic et al. 1998; Kim et al. 2010; Carnero and Paramio 2014; Xu et al. 2014).