ESR1 and non-functioning pituitary adenoma: The very interesting thing is that the silent hormone expressed in an NFPA tissue associates tumor biological behaviors, such as invasive characteristics (7, 8); for example, a clinically silent corticotroph tumor of a pituitary shows symptomatic cystic degeneration (7), and estrogen receptors and slug contribute to development of invasiveness of an NFPA (8).