Pituitary adenoma or pituitary neuroendocrine tumor: a narrative review of controversy and perspective

In 1932, Harvey Cushing first proposed pituitary adenoma (PA) as the term for the cause of acromegaly. After nearly 90 years of research, PA is recognized as the second most common intracranial neoplasm. Most PAs can be easily cured or controlled by conventional therapies, including surgery, medical treatment or radiotherapy. However, nearly 40% of PAs are invasive, and some adenomas show aggressive behavior, with rapid growth patterns and resistance to conventional treatments, which leads to a poor prognosis; this type of adenoma is called aggressive or refractory PA. For a very small proportion of PAs (approximately 0.2%), subarachnoid or systemic metastasis may develop, at which point it is considered malignant and called pituitary carcinoma. Based on distinctions regarding the biological behaviors of adenoma, aggressive adenoma and pituitary carcinoma, the International Pituitary Pathology Club in 2016 formally proposed new terminology for PA: pituitary neuroendocrine tumor (PitNET). Over the last three years, an increasing number of relevant articles have used the term PitNET in place of PA. Interestingly, the fourth edition of the WHO classification of PA released in 2017 did not adopt this nomenclature, and the Pituitary Society published a paper in 2019 suggesting that the new nomenclature does not improve clinical diagnosis or treatment and confuses patients more than the PA terminology. The Pituitary Society insists on using the term PA, as PAs with aggressive behavior only account for a very small proportion of all PAs. Overall, the new terminology may cause significant and unnecessary patient anxiety and confusion. Here, we describe the current perspectives and bases of the two naming methods and offer our opinions on maintaining the original naming system for PA. Nevertheless, early diagnosis and intensive treatment of aggressive PAs is extremely important for improving patient prognosis, regardless of the nomenclature.