Purpose: Somatotroph pituitary neuroendocrine tumors are classified into sparsely and densely granulated tumor patterns. This study tried to find a positive correlation between the intensity of growth hormone expression in histopathology and the clinical presentation as well as the surgical outcome and requirement for adjuvant treatment.
Methods: Patients with a immunohistochemistry diagnosis of a growth hormone PitNET and undergoing a transnasal transsphenoidal surgery at the CHUV neurosurgery university center between January 2012 and December 2020 with a follow-up of at least six months were included in this research. Results of histopathological analysis reports were collected and compared with extent of resection and presence of residual tumor, biological remission and rate of tumor recurrence over the follow-up period as well as radiological features of invasion in the preoperative imaging, hormonal profiles of GH and IGF-1 before and after surgical intervention, association with typical clinical features of acromegaly, need for a secondary neurosurgery and adjuvant treatments.
Results: Data of thirty seven patients was analysed in this research. Results of pre-operative OGTT tests were positively correlately with the intensity of histopathological growth hormone expression (p = 0.03). Biochemical remission at one week and three months after surgery were also significantly higher in tumors with a weaker growth hormone expression (p = 0.037 and 0.08). No association was found between GH expression and tumor recurrence (p = 1) or gross total resection (p = 0.5). No statistical difference was found between tumor size and pre-surgical GH expression (rs = -0.1377, p (2-tailed) = 0.48469) or post-surgical GH expression (rs = 0.13457, p (2-tailed) = 0.54041). Concerning pre-surgical radiological features, tumors with a weak GH expression surpassed double in volume tumors with a strong GH expression (4.311 ± 6.603 vs 2.169 ± 2.441 cm3), which resulted in higher rates of mass effect on the optic chiasma (53.3% vs 31.8%, p = 0.31). However, no disparity was found between the two tumor groups concerning pituitary stalk displacement (80.9% vs 86.7%, p = 1) nor Knosp grades (Knosp 3 and 4 respectively 28.6% vs 33.3%, p = 1). In general, comorbidities in patients with a somatotroph tumor displaying a higher GH expression were more prevalent although never significatively: sleep apnea syndrome (p = 0.15), glucose intolerance and type II diabetes (p = 0.73), cardiovascular diseases (p = 0.70, hypertension (p = 0.31), higher obesity rates (p = 0.12), arthropathy (p = 0.74) and colon polyps (p = 0.06). All somatostatin analogs were prescribed for tumors with a strong GH expression (p = 0.063). The same proportion of patients in each group were benefitted Gamma-Knife neurosurgery (p = 1) and required a second surgery (p = 1).
Conclusion: Expression of growth hormone in histopathology was indeed correlated with pre-operative OGTT test results, remission at one week and three months. Tumors with a stronger GH expression caused a greater number of comorbidities in patients but not significatively. All somatostatin analogs were only prescribed to tumors with a strong GH expression. No difference was found for the need of a second surgery, tumor persistence, need for Gamma-Knife neurosurgery and tumor size.