New pathological classification and clinical implications of pituitary neuroendocrine tumors of the 2022 WHO version

Abstract

In 2022, the World Health Organization proposed a new classification for pituitary adenomas. The major nomenclature change from the previous edition was the transition from"adenoma"to"pituitary neuroendocrine tumor"(PitNETs). The new classification provided the detailed histological subtypes of PitNETs for routine use of antibodies such as pituitary transcription factors (PIT1, TPIT, SF1, GATA3, and ERα) and hormones. The major PIT1, TPIT, and SF1 lineage-defined PitNETs types and subtypes featured distinct morphologic, molecular, and clinical differences. Unlike the 2017 WHO classification, the 2022 WHO version updated some concepts as follows: (1) Mammosomatotroph, acidophil stem cell tumors and mixed somatotroph/lactotroph tumor represented distinct PIT1-lineage PitNETs; (2) The diagnostic category of PIT1-positive plurihormonal tumor was replaced by the immature PIT1-lineage tumor and the mature plurihormonal PIT1-lineage tumor; (3) The term"metastatic PitNET"was advocated to replace the previous terminology"pituitary carcinoma". The new classification emphasizes the importance of pathological classification of PitNETs. Obviously, accurate pathological interpretation is the key to judge the clinical treatment pathway and prognosis of patients.