SSTR2 expression in neoplastic and normal anterior pituitary is impacted by age, sex, and hormonal status

Pituitary neuroendocrine tumors (PitNETs) are among the most common tumors encountered in neurooncology. While the majority of PitNETs demonstrate indolent behavior, a subset of tumors demonstrates aggressive behavior, including invasion into surrounding structures. As traditional imaging has limited capacity to distinguish tumor from post-operative changes, better methods of tumor delineation are needed to guide management. Somatotroph adenomas are known to express high levels of SSTR2, and SSTR2-targeting PET imaging has shown clinical utility in the management of neuroendocrine tumors and meningiomas. In this retrospective study of archival PitNETs (n = 271) and autopsy controls (AC) (n = 20), we show that although significant differences in SSTR2 immunostaining are appreciable between adenoma subtypes and ACs, high-staining cases are encountered in all subtypes. In ACs, females demonstrated significantly stronger SSTR2 staining than males. Weak age-related trends towards increasing labelling in females and decreasing labelling in males were noted but these did not reach statistical significance. Decreasing age-related trends were seen in gonadotrophs in both sexes; this was statistically significant in females. Our findings suggest that SSTR2-targeting imaging modalities may assist clinical management of a subset of PitNETs and that these results may need to be interpreted with consideration of patient age and sex.