Twenty-two pancreatic islet cell tumors and normal pancreatic islets from ferrets were evaluated by immunohistochemistry for expression of the peptide hormones insulin, somatostatin, glucagon, and pancreatic polypeptide (PP) and the neuroendocrine markers chromogranin A (CgA) and neuron-specific enolase (NSE). In normal pancreatic islets, the majority of cells stained strongly with CgA and NSE. A cells, B cells, D cells, and PP cells stained strongly with glucagon, insulin, somatostatin, and PP, respectively. All 22 tumors stained with CgA and NSE. The proportion of cells within tumors staining for CgA was variable, but more than half of the cells stained positively in 18 of the tumors. The intensity of staining for CgA was strong (reactivity equivalent to or greater than normal islet cells in adjacent tissue) in 11 moderate in six, and weak in five of the tumors. All tumors stained for NSE, with ≥50% of the cells staining in 21 of the tumors, and the intensity of staining was strong in 18 of the tumors. Twenty of 22 tumors stained positively for insulin, with ≥50% of the cells staining in 19 of them. The intensity of staining for insulin was strong in 12, moderate in seven, and weak in one of the tumors. Approximately ≤1% of the cells in 15 of 22 tumors stained for somatostatin, five tumors stained for pancreatic polypeptide, and three tumors stained for glucagon. These data indicate that the majority of islet cell tumors of ferrets express immunohistochemically detectable insulin. CgA and NSE are both useful general markers for such tumors, including those that are insulin negative. Commercially available antisera to CgA, NSE, insulin, glucagon, somatostatin, and PP work well in formalin-fixed, paraffin-embedded tissue for immunophenotyping islet cell tumors in the ferret.
Non-Islet Origin of Pancreatic Islet Cell Tumors
