Multiple Glucagon-Producing Pancreatic Neuroendocrine Tumors in a Horse (Equus caballus)

Abstract

Pancreatic neuroendocrine tumors of glucagon-producing cells are extremely rare in domestic animals. In this report, we describe for the first time, to our knowledge, the incidental finding of multiple glucagon-producing neuroendocrine tumors of the pancreas of a horse. The animal was euthanized due to severe local infection after tooth extraction. On postmortem examination, multiple white nodules of up to 4 cm in diameter were observed in the pancreas. Histologically, pancreatic nodules had the appearance of neuroendocrine neoplasms with positive immunoreactivity for glucagon, synaptophysin, chromogranin A, and neuron-specific enolase. Electron microscopy revealed numerous electron-dense granules, similar to those observed in normal pancreatic alpha cells, in the neoplastic cells. In addition, the left adrenal gland showed multiple hyperplastic foci and adenomas in the medulla that were identified as pheochromocytomas. Based on the morphologic appearance and immunohistochemical staining pattern of pancreatic nodules, a diagnosis of multiple glucagon-producing neuroendocrine tumors was made.

Malignant glucagonoma associated with hyperglycaemia, hypertriglyceridaemia, Candidiasis and bacterial pneumonia in a 12‐year‐old Arabian gelding

“…The only other report of equine glucagonoma was considered to be an incidental finding at necropsy as no clinical signs were reported (Herbach et al . ). Glucagon is a hormone secreted by alpha cells in the pancreas with the primary function of increasing blood glucose and has a wide range of physiologic activity, including stimulation of lipolysis, gluconeogenesis, glycogenolysis and activation of cyclic‐AMP.…”

“…A single case report describes a glucagonoma in a horse (Herbach et al . ). The authors of that report considered the tumour to be an incidental finding with no related clinical signs.…”

“…Pancreatic disease in horses is also uncommon with conditions such as pancreatic adenoma, adenocarcinoma, non‐functional alpha‐cell adenoma, insulinoma and pancreatitis rarely reported (Herbach et al . ; Newman ). In all cases of pancreatic disease, establishing an ante‐mortem diagnosis is difficult due to the anatomic location of the equine pancreas and the non‐specific clinical and blood chemistry values associated with pancreatic disease in horses (Johnson et al .…”

Endocrine tumours in equids

“…There is only one report of an insulinoma in a Shetland pony showing hypoglycaemic seizures (Ross et al 1983). Similarly, only one description of a case with multiple pancreatic glucagonproducing adenomas is available (Herbach et al 2014). This latter horse lacked any clinical signs typically associated with glucagonomas in other species, such as diabetes mellitus or skin lesions.…”

Occurrence of elevated amylase and lipase enzymes in horses with gastrointestinal disease

“…Postmortem findings include acute, chronic and chronic active pancreatitis (Breider et al 1985, Taintor et al 2006, Bakos et al 2008, Talbot et al 2011, Ollivett et al 2012, Yamout et al 2012, Newman 2015 and neoplasia (Ross et al 1983, Church et al 1987, Carrick et al 1992, Rendle et al 2006, Barsnick et al 2008, Spanton et al 2009, Brot et al 2014, Herbach et al 2014.…”