Normal pituitary showed strong homogeneous membranous β-catenin staining, whereas absent or weak granular membranous beta-catenin expression was observed in 40% of sporadic tumors and 83% of AIPpos tumors (AIPpos vs. normal pituitary P = 0.01, AIPpos vs. sporadic somatotrophinoma P = 0.04) (Fig. 2b). This evidence concerns the gene CTNNB1 and growth hormone-producing pituitary gland adenoma.