Introduction: Acromegaly is caused by lesions which are primarily growth hormone (GH) secreting;
however, a subset of tumors also stain positive for prolactin (PRL). Although previous
studies have examined the incidence and histological characteristics of these lesions,
little has been documented regarding the clinical/endocrinological characteristics
and postoperative outcomes after transsphenoidal surgery (TSS).
Objectives: In this preliminary study, we examined the clinical characteristics and postoperative
outcomes in acromegaly patients with PRL positive lesions.
Methods: In this single institution, retrospective study, a large cohort of 156 acromegaly
patients who had GH and PRL staining data available between 2008–2024 were examined.
Radiological, surgical, clinical, and endocrinological characteristics at baseline
and postoperatively were tracked. Pituitary adenoma size, location, and dimensions
were determined using preoperative magnetic resonance imaging (MRI) and computed tomography
(CT) imaging. t-tests and chi-square tests were not performed due to the high type-1 error rate.
A multivariate logistic regression model was created to determine whether PRL co-staining
was predictive of postoperative complications, biochemical remission, or recurrence.
Results: Among the 156 patients with staining data available, 95 (60.9%) demonstrated PRL
immunopositivity. The most common preoperative symptoms on presentation were headache
(42.1 vs. 39.3% in PRL+ vs. PRL− patients, respectively), acromegalic-bone changes
(72.6 vs. 78.7%), and tumor-induced visual loss (21.1 vs. 19.7%, respectively). Preoperative
demographics, as well as the rates of preoperative comorbidities and medication prescription
were largely similar between groups. Preoperatively, GH hypersecretion occurred in
84.8% of PRL+ and 83.3% of PRL- lesions. Unsurprisingly, rates of preoperative hyperprolactinemia
were higher in the PRL+ group (26.4 vs. 8.8%, respectively). Hypogonadism and hypocortisolism
were common in both groups (17.9 and 12.8%, respectively, overall). Postoperatively,
rates of GH hypersecretion were similar between groups (29.6 vs. 26.2% in PRL+ vs.
PRL−, respectively). Rates of hypoadrenalism were higher in the PRL+ group (116.3
vs. 5.1%), and no other significant differences in postoperative endocrine dysfunction
were noted. Interestingly, rates of tumor adherence and parasellar location were higher
in the PRL- group (16.4 vs. 5.3%, and 9.1 vs. 0%. respectively). PRL+ lesions had
higher MIB index scores (2.74 ± 2.4 vs. 1.6 ± 0.9, respectively) and experienced higher
rates of cystic features (20.2 vs. 9.3%). Furthermore, the rates of p53, ACTH, and
FSH immunopositivity were higher in the PRL+ group (68.7 vs. 35.6%, 31.6 vs. 13.1%,
and 10.5 vs. 1.7%, respectively). All but two patients received endoscopic TSS, with
nasal packing and fat grafting being the most common sellar reconstruction methods
used. Postoperatively, the rates of gross total resection (84.2 vs. 83.6%), biochemical
remission (75.4 vs. 75.5%), and recurrence (11.6 vs. 6.6%) were largely similar. Multivariate
logistic regression demonstrated that PRL immunopositivity was not associated with
a significantly increased risk of developing surgical complications (dysnatremia or
CSF leak), a failure to achieve biochemical remission, or recurrence when adjusted
for covariates.
Conclusion: Overall, despite distinct preoperative endocrinological and histological landscapes,
PRL immunopositivity in acromegaly patients was not associated with worse postoperative
outcomes. In the future, we aim to perform double staining to further classify PRL+
lesions as monomorphic or dimorphic lesions.
