Pituitary tumors: Changing paradigms in understanding, nomenclature and the newer basis of classification

The pituitary gland is embryologically divided into two main lobes: adenohypophysis (anterior) and neurohypophysis (posterior). Last five decades have witnessed changes in the tumor classifications – anterior pituitary in 2017 and posterior in 2016, based on hormonal immunohistochemistry, molecular profiles, and pituitary specific transcription factors. Few newer entities/terms have been added and at the same time certain terms have been modified/discarded. In this article, relevant anatomy, development, histology, incidence, and clinical manifestations of pituitary tumors evolution of various classification systems and recommended current classification of pituitary tumors; the genetic alterations and the diagnostic implications for today's pathologist have been reviewed in a comprehensive manner.