Imaging of pituitary tumors: an update with the 5th WHO Classifications—part 1. Pituitary neuroendocrine tumor (PitNET)/pituitary adenoma

Abstract

The pituitary gland is the body’s master gland of the endocrine glands. Although it is a small organ, many types of tumors can develop within it. The recently revised fifth edition of the World Health Organization (WHO) classifications (2021 World Health Organization Classification of Central Nervous System Tumors and 2022 World Health Organization Classification of Endocrine and Neuroendocrine Tumors) revealed significant changes to the classification of pituitary adenomas, the most common type of pituitary gland tumor. This change categorized pituitary adenomas as neuroendocrine tumors and proposed the name to be revised to pituitary neuroendocrine tumor (PitNET). The International Classification of Diseases for Oncology behavior code for this tumor was previously “0” for benign tumor. In contrast, the fifth edition WHO classification has changed this code to “3” for primary malignant tumors as same to neuroendocrine tumor in other organs. Because the WHO classification made an important and significant change in the fundamental concept of the disease, in this paper, we will discuss the imaging diagnosis (magnetic resonance imaging, computed tomography, and positron emission tomography) of PitNET/pituitary adenoma in detail, considering these revisions as per the latest version of the WHO classification.

Ectopic Pituitary Neuroendocrine Tumors/Adenomas Around the Sella Turcica

“… 16 , 17 , 18 , 19 Additionally, neuroendocrine proteins such as chromogranin A, insulinoma-like protein 1, CD56, and synaptophysin are expressed by PitNETs, which are suggestive of neuroendocrine tumors. 20 …”

From pituitary adenoma to PitNET: it is time to discuss PitNET/pituitary adenoma

“…As we have been familiar with "pituitary adenoma" for many years, it will take longer time for PitNET to gain social consensus and recognition [2,4].…”

“…Until the term PitNET is widely accepted by most physicians, it may be advisable to include the name pituitary adenoma along with the new name PitNET in the radiology report [2]. Except pathologists, neurosurgeons, and endocrinologists, it is radiologists who have many opportunities to use the term "PitNET".…”

“…The 5th edition of the WHO Classifications (2021 World Health Organization Classification of Central Nervous System Tumors and 2022 World Health Organization Classification of Endocrine and Neuroendocrine Tumors) has made significant changes, including classification of tumors based on cell lineage as determined by expression of transcription factors, hormones, and other biomarkers [1]. Faced with many updates as described in the articles [2,3], it is important for radiologists to understand the pros and cons of these updates.…”

Differentiation of silent corticotroph pituitary neuroendocrine tumors (PitNETs) from non-functioning PitNETs using kinetic analysis of dynamic MRI

“…Pituitary adenomas, described as pituitary neuroendocrine tumors (PitNETs) in the 5th edition of the World Health Organization (WHO) Classifications (2021 WHO Classification of Central Nervous System Tumors and 2022 WHO Classification of Endocrine and Neuroendocrine Tumors) [1], are the most common intracranial endocrine tumors and are broadly classified clinically into functioning adenomas that produce hormones and non-functioning adenomas (NFAs) that do not produce hormones. NFAs account for approximately 15-54% of pituitary adenomas [2,3].…”