[WHO Histological Classification of Pituitary Tumors]

The major changes in the upcoming 5^th edition of the "2022 WHO Classification of Endocrine and Neuroendocrine Tumors" include:(1)evolution of the nomenclature: from pituitary adenoma to pituitary neuroendocrine tumour(PitNET),(2)detailed subtyping of a PitNET based on the tumor lineage, cell type, and related characteristics,(3)endorsement of the routine use of immunohistochemistry for pituitary transcription factors(PIT1, TPIT, SF1, GATA3, and ER-alpha),(4)introduction of some additional clinicopathologically distinct PitNET subtypes,(5)introduction of the term "metastatic PitNET" to replace the previous terminology "pituitary carcinoma," and(6)unifying posterior lobe tumors, the family of pituicyte tumors that invariably express TTF1, et al. Currently, no widely agreed grading or staging systems for PitNETs exist. Prognosis varies by tumor subtype and certain tumor subtypes are recognized as more aggressive(high-risk PitNETs)than others. Potentially aggressive PitNETs should be identified on an individual basis upon considering the tumor subtype, proliferative potential, and tumor invasion assessment.