Clinicopathologic Analysis of 43 Surgically Resected Lactotroph Pituitary Neuroendocrine Tumors Stratified by Surgical Indication

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Abstract
Male lactotroph pituitary neuroendocrine tumors (PitNETs) are often considered more aggressive than those in women, but surgically treated cohorts are highly selected and may reflect differences in presentation and indication for surgery. We examined whether advanced clinical presentation in surgically treated lactotroph PitNETs is accompanied by distinct pathologic features. We reviewed 43 patients who underwent surgery for lactotroph PitNETs between 2018 and 2023 at a high-volume referral center. Cases were classified by surgical indication as preference for surgery/intolerance to dopamine agonists (P/I, n=26), resistance with hormonal symptoms (R/H, n=10), and resistance with mass effect (R/M, n=7). Clinical, radiologic, and pathologic parameters, including Ki-67, cytokeratin (CAM5.2), estrogen receptor, somatostatin receptor 2/5, and O6-methylguanine-DNA methyltransferase, were compared. Postoperative endocrinological remission was assessed at the last follow-up (median: 34 mo). All tumors were prolactin-immunoreactive, confirming lactotroph differentiation. Patients in the R/M group were older (median: 56 y), predominantly male (71.4%), and had larger tumors (median: 26 mm) with more frequent cavernous sinus invasion (Knosp grade 4, 85.7%) than those in the other groups. Long-term endocrinological remission differed significantly by indication (P/I, 88.5%; R/H, 80.0%; and R/M, 0%). In contrast, Ki-67 labeling index did not differ significantly across groups (P/I, 1.3%; R/H, 1.5%; and R/M, 2.6%; P =0.598), and no clear between-group differences were identified in CAM5.2 pattern, estrogen receptor, somatostatin receptor 2/5, or O6-methylguanine-DNA methyltransferase status. These findings suggest that the clinically most advanced surgical cases are not matched by distinct pathologic differences in the markers assessed and that the apparent aggressiveness of male-predominant mass-effect cases should not be interpreted solely as reflecting intrinsically aggressive tumor biology.
Funding Information
  • Ministry of Education, Culture, Sports, Science and Technology (JSPS KAKENHI (Grant Number 19K07427))
  • MHLW Program for Research on Rare and Intractable Diseases (JPMH23FC1042)

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