Distribution Characteristics and Clinical Significance of Peripheral Blood Lymphocyte Subsets in Patients with Pituitary Neuroendocrine Tumors

Objective To investigate the distribution characteristics of peripheral blood lymphocyte subsets in patients with Pituitary Neuroendocrine Tumors (PitNETs) based on the 2022 WHO classification and analyze their relationship with clinical features of the tumors. Methods A total of 230 patients with pathologically confirmed PitNETs admitted to the Department of Neurosurgery, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences between March and October 2023 were enrolled. Absolute counts and percentages of peripheral blood lymphocyte subsets (T cells, B cells, NK cells, and CD4+/CD8 + T cell ratio) were detected by flow cytometry and compared with reference values from healthy adults. Subgroup analyses were performed according to the 2022 WHO classification (PIT1, TPIT, SF1 lineages, etc.), clinical functional type, and Knosp grading. Results Compared with the normal population, PitNETs patients overall showed decreased absolute lymphocyte count and NK cell proportion, while B cell proportion, T cell proportion, and CD4+/CD8 + T cell ratio were increased (all P < 0.05). This trend was consistent across PIT1, TPIT, and SF1 lineage tumors. Subgroup analysis revealed that these alterations were most pronounced in non-functioning adenomas and growth hormone (GH) adenomas. Correlation analysis found that larger tumor volume (r = -0.114, P < 0.05) and higher Knosp grade (r = -0.046, P < 0.05) were associated with lower B cell proportion; whereas higher Knosp grade was associated with a higher CD4 + T cell proportion (r = 0.112, P < 0.05). Lymphocyte distribution was not significantly correlated with tumor recurrence. Conclusion Patients with PitNETs exhibit systemic immune dysfunction, characterized by abnormalities in both cellular immunity (decreased NK cells) and humoral immunity (increased B cells). This immune dysregulation is associated with tumor lineage, size, and invasiveness. Analysis of peripheral blood lymphocyte subsets may provide a new clinical perspective for assessing the immune status of PitNETs and exploring their potential for immunotherapy.