Somatostatin Receptor 2 and 5 Expressions in Gastroenteropancreatic Neuroendocrine Tumors in Turkey

Background: Gastroenteropancreatic neuroendocrine tumors (GNs) are slow growing and although theirincidence has increased in recent years, they are relatively rarely seen. Somatostatin analogues are used inthe treatment of GNs that express somatostatin receptor (SR). We aimed to investigate the expression ofSR2 and SR5 in GNs. Materials and
Methods: In this study the expression of SR2 and SR5 was investigatedimmunohistochemically in 49 cases (26 males, 23 females) diagnosed and graded with GN according to the WorldHealth Organization classification 2010.
Results: The percentage of SR2 staining was 91.0% in grade 1, 82.8%in grade 2 and 100% in grade 3. On the other hand, the percentage of SR5 staining was 81.8% % in grade 1,60.0% in grade 2 and 0% in grade 3. According to the tumor localization, the percentages of SR2 expressionwere as follows: pancreas 85.7%, stomach 100%, small bowel 70%, appendix 85.7% and rectum 100%. Thepercentages of SR5 expression were: pancreas 61,9%, stomach 37.5%, small bowel 70%, appendix 71.5%and rectum 66.6%. There was a significant negative correlation between ki67 percentage and SR5 expression(r=-0.341, p=0.016).
Conclusions: In this study, GNs were found to highly express SR2 and SR5. Although theexpression of SR2 and SR5 changed according to tumor localization, the expression of SR2 was higher than theexpression of SR5 in GN. There was a significant negative correlation between ki67 and SR5. Accordingly, SR5may be a prognostic indicator of GN.