[Histological Classification and Diagnosis of Sellar/Parasellar Tumors]

In the 5^th edition of the WHO classification of pituitary tumors, there are several significant changes:(1)the nomenclature has evolved from "pituitary adenoma" to "pituitary neuroendocrine tumor"(PitNET);(2)PitNETs are now categorized in detail based on tumor lineage, cell type, and related characteristics;(3)the routine use of pituitary transcription factor(PIT1, TPIT, SF1)immunohistochemistry for PitNET classification;(4)there is a distinction between two types of craniopharyngioma(CP), adamantinomatous CP and papillary CP, characterized by CTNNB1(β-catenin)and BRAF mutations, respectively;(5)the integration of four subtypes of posterior lobe(neurohypophysial)tumors, known as the family of pituicyte tumors that express TTF1, is emphasized. Regarding tumor proliferation markers, the assessment of the Ki-67 proliferation index remains important, although no specific cutoff value was provided. Certain PitNET subtypes have been recognized as clinically more aggressive, referred to as high-risk PitNETs. However, it is worth noting that the classification does not introduce a new grading system for PitNETs.