A functional, insulin-secreting pancreatic (islet cell) carcinoma was diagnosed in a 17-year-old male Siamese cat. Diagnosis was made on the basis of clinical signs (i.e., seizures and stupor) that resolved temporarily after correction of hypoglycemia with feeding or intravenous administration of glucose, the finding of an inappropriately increased serum insulin concentration in the face of hypoglycemia, and prolonged resolution of hypoglycemia after surgical removal of the tumor. Primary islet cell tumor of the pancreas was confirmed by biopsy. The cat died 18 months later, and necropsy revealed metastases to regional lymph nodes and liver. INSULIN-SECRETING pancreatic (islet cell) tumors leading to hypoglycemia are well recognized in human beings,' dogs,*-' and ferrets,6 but they have not been well documented in cats. This report describes the clinical, serum biochemical, and pathologic findings in an elderly cat with an insulin-secreting tumor of the pancreas.
Materials and MethodsSerum insulin was measured with a commercial radioimmunoassay kit.* Assay of serial dilutions of a feline serum pool containing increased insulin concentrations (approximately 400 pmol/L) resulted in inhibition curves with slopes parallel with the standard curve. Accuracy was determined by adding various quantities of purified pork regular insulin to a feline serum pool containing an undetectable concentration of insulin; analysis of the resulting data revealed an average recovery of 94%. The sensitivity of the insulin assay was 35 pmol/L. The intra-and interassay coefficients of variation were 8.1% and 1476, respectively. Immunocytochemical staining was done with the avidin-biotin-peroxidase complex immunoperoxidase method as previously described,'.* with polyclonal antibodies against guinea pig insulin,t porcine glucagon,? human gastrin,? pancreatic polypeptide,? and somatostatin? and bovine neuron specific enolase,? and chromogranin A.S
Case ReportA 17-year-old male castrated Siamese cat was examined because of previously diagnosed hypoglycemic seizures. The seizures were grand mal, unassociated with meals, and responsive to oral corn syrup. The seizures had begun 18 months previously and were increasing in frequency.Three and 1 1 months before examination, the cat had two episodes of severe regenerative anemia (PCV =
Abstract. Immunocytochemical studies of the distribution of glucagon, gastrin, insulin, and somatostatin in normal canine pancreatic islets and 20 canine islet cell tumors were done using the peroxidase-anti-peroxidase (PAP) technique. In the normal adult canine pancreas, islets typically consisted of clusters of [20][21][22][23][24][25][26][27][28][29][30] Pancreatic endocrine tumors could previously only be classified as p and non-p-cell tumors by either conventional light microscopy with special stains or by electron microscopic identification of specific secretory granule morphology. Pancreatic islet cell tumors can be classified by the immunocytochemical demonstration of specific antigens representing the various pancreatic polypeptide hormones. The technique is also useful in identification of metastatic neoplasms of presumed pancreatic endocrine origin. Retrospective studies using formalin-fixed, paraffin-embedded tissue are now possible using the PAP immunocytochemical technique.Embryologically, the endocrine and exocrine cells of the pancreas have a common endodermal origin arising from ductal structures branching from the primitive foregut.4,s,16,18,24,56 Pluripotent cells within the fetal pancreatic ducts proliferate, evaginate, detach from the duct and vascularize to form individual islet^.^,^^,^^ Endocrine cells can occasionally be seen interposed between exocrine ductal epithelial cells, even after the islets are fully formed.8J6,24,40,55 Pancreatic islet cells were once thought to be of ectodermal origin since they concentrate and decarboxylate amine precursors (APUD cell^);^^^^^^^ this concept has been d i~p r o v e n .~,~~The immunocytochemistry of the normal endocrine pancreas has been well-described in man16x21,47g55,61 and less so in anima1s.5,6J7,22*25,3 Six hormones have been identified immunocytochemically in the normal adult islets of Langerhans of man: insulin, glucagon, somatostatin, gastric inhibitory polypeptide (GIP), vasoactive intestinal polypeptide (VIP), and pancreatic polypeptide (PP). 16,21,56,61 Insulin, glucagon, somatostatin, and pancreatic polypeptide have been demonstrated by light microscopy with special stainsY4J8J9 ultrastructurally,9~1s~1g~36~57 or immunocytochemica11y22,25,33 in the dog pancreas (Table 1). G cells containing gastrin have been identified immunocytochemically in the human fetal and neonatal pancreas, but are absent in normal mature islet cell populat i o n~.~~,~~,~~,~~ G cells are normally found in the mucosa of the pyloric antrum and proximal duodenum of man47,48 and the adult Islet cell tumors are uncommon in man and can cause a variety of clinical ~y m p t o m s ;~~,~~,~~ however, many are poorly functional or non-functional and are often clinically ~i l e n t .~J~,~~ Insulinomas are the most frequently occurring pancreatic endocrine neoplasm of mans6 followed by gastrinomas.8J6 Ninety percent of insulinomas are whereas the majority of the less frequently occurring pancreatic endocrine neoplasms are malignant.8J6,56 Malignant pancreatic endocrine tu...
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