Pituitary Neuroendocrine Tumor: Is It Benign or Malignant?

The World Health Organization (WHO) updated the classification of pituitary tumors in 2022. The new classification presents detailed histological subtyping of a pituitary neuroendocrine tumor (PitNET) based on the tumor cell lineage, cell type, and related characteristics. The immunohistochemistry for pituitary transcription factors (PIT1, TPIT, SF1, GATA3, and ERα) is routinely needed in this classification. The controversy regarding the change of behavior code of all PitNET/pituitary adenoma from "0" for benign tumors to "3" for primary malignant tumors is a topic of debate among experts, nowadays. Some authors represent that pituitary adenoma has a tendency for hemorrhage and necrosis and frequent invasion of the cavernous sinus. However, most small PitNET/pituitary adenoma do not need any treatment because of benign biologic behavior or less than 5% recurrence after gross total removal. Pituitary apoplexy is also benign nature but has a tendency of cranial nerve compression or panhypopituitarism. Most of cavernous invasion is compression of the cavernous sinus. Aggressive PitNET/pituitary adenoma with malignant biological behavior is less than 1%.