Molecular biology of pituitary tumors

Pituitary neoplasms are relatively common tumors that demonstrate a wide range of hormonal and proliferative behaviours. The diversity in their hormonal activity reflects their complex cytodifferentiation. It was believed that 1 cell of adenohypophysis could produce only 1 hormone. However, advances in immunocytochemistry, electron microscopy, and molecular studies have led to a new classification of pituitary tumors and a better understanding of the mechanisms that determine development of these neoplasms. The heterogeneity of pituitary adenoma subtypes suggested that no single common etiologic event was responsible for the development of adenoma. Molecular studies within the last decade have provided evidence that multiple molecular events are involved in the pathogenesis of pituitary adenomas. These series of molecular events supported the modem theory of multistep tumorigenesis. The objective of this review is to shed light on the molecular pathogenesis and histologic classification of adenohypophyseal neoplasms based on the recent biochemical results, molecular studies, and clinicopathologic findings. Understanding the genetic defects of pituitary tumors allows a deeper insight in the pathogenesis and biologic behaviour of pituitary tumors and can lead to the development of a novel approach for the management of patients with pituitary tumors.