Despite designated markers associated with invasive behavior of PA tumors such as the Ki-67 proliferative index, the number of mitotic figures, and the expression of p53 (48, 49), the early prediction of PA invasiveness is still considerably hard, since the patient's state tends to be delayed due to the clinical symptoms of NFPA which are not obvious in the early stage. This evidence concerns the gene TP53 and non-functioning pituitary adenoma.