Redefining Pituitary Neuroendocrine Tumors in MEN1: Prevalence, Clinical Behavior, and Implications for Long-Term Surveillance.

backgroundPituitary neuroendocrine tumors (PitNETs) are a core manifestation of multiple endocrine neoplasia type 1 (MEN1), yet their true prevalence, biological behavior, and optimal management remain debated. Earlier reports suggested increased aggressiveness compared with sporadic PitNETs, while more recent surveillance-based studies indicate a predominantly indolent phenotype.

methodsWe conducted a retrospective single-center study including all patients with clinical, familial, or genetic MEN1 referred to the Endocrinology Unit of the University of Naples "Federico II", ENETS Center of Excellence, between January 2004 and June 2025. Demographic, clinical, radiological, hormonal, and therapeutic data were systematically collected. PitNETs were classified by size and hormonal activity.

resultsAmong 103 MEN1 patients (61 women), 50 (48.5%) were diagnosed with PitNETs at a mean age of 35.1 years. Microadenomas predominated (60%), and tumors were equally distributed between functioning and non-functioning lesions. Prolactin-secreting PitNETs were the most common functioning subtype (42%), followed by rare GH-, ACTH-, or mixed-secreting PitNETs. Dopamine agonists, mainly cabergoline, were prescribed in 38% of cases, while neurosurgical intervention was required in 14%, exclusively for macroadenomas. During follow-up, recurrence occurred in 8% of patients. No significant sex-related differences were observed in prevalence, tumor size, functional status, treatment approach, or outcomes.

conclusionsIn our MEN1 cohort, PitNETs were frequent but largely indolent, with a predominance of microadenomas and limited need for surgery. Our findings support individualized, subtype-driven surveillance strategies, with conservative management for clinically non-functioning microadenomas and closer monitoring of prolactin-secreting PitNETs due to variable medical responsiveness.