A Single-Center Retrospective Analysis: The Correlation Of Grade, Chromogranin-A, Sst2 Ihc Stains, And Octreoscan Imaging In Small Bowel And Pancreatic Nets.

e14585 Background: Previous analyses have demonstrated that neuroendocrine tumor (NET) grade correlates well with OctreoScan positivity, SST2, and Chromogranin-A immunohistochemical (IHC) staining. Historically lower grade tumors were more likely to have a higher amplification of STT2 receptors and OctreoScan positivity. There have however been reports of pancreatic neuroendocrine tumors expressing a high degree of SST2 receptors. We hypothesized that tumor origin Chromogranin-A (ChrgA) and SST2 IHC staining would correlate with OctreoScan positivity and Wick's grade, but were unsure if this would be the case with pancreatic NETs. Methods: We retrospectively analyzed 79 formalin-fixed paraffin-embedded tumor specimens based on tumor histological origin for 1) Wick's tumor grade, 2) SST2 receptor, and 3) ChrgA IHC staining. We sought to primarily analyze NETs of the small bowel and pancreas. CT scan evidence of stage IV disease was corroborated with OctreoScan imaging, but only pancreatic primaries were assessed. OctreoScan imaging was graded as positive or negative. Wick's grading system of: 1 = well differentiated; 2 = moderately differentiated; 3 = poorly differentiated; SST2 and ChrgA IHC stains were performed and graded: 1 +, 2+ or 3+. Results: See Table. Conclusions: Although published reports have demonstrated a higher correlation of OctreoScan positivity with lower grade neuroendocrine tumors, our results demonstrate that pancreatic neuroendocrine tumors were consistently higher grade, OctreoScan positive, and ChrgA and SST2 rich. Small bowel tumors were more likely to be lower grade (Wick's grade 1-2) as consistent with published reports. ChrgA and SST2 IHC staining of 2-3+ appeared to correlate with Wick grade in NETs of the small bowel, but were neither sensitive nor specific in those of pancreatic neuroendocrine origin. Primary tumor (NETs) Wick grade 1 Wick grade 2 Wick grade 3 Small bowel 21/56 26/56 9/56 Pancreatic 3/23 8/23 12/23 Chromogranin-A IHC STAIN Small bowel tumors Pancreatic tumors 1+ 2/56 2/23 2+ 5/56 3/23 3+ 49/56 17/23 Neg 0/56 1/23 SST2 IHC STAIN Small bowel tumors Pancreatic tumors 1+ 23/56 3/23 2+ 16/56 10/23 3+ 14/56 8/23 Neg 3/56 2/23 No significant financial relationships to disclose.