Gastric Neuroendocrine Carcinomas in Bearded Dragons (Pogona vitticeps)

Abstract

This article describes a newly recognized highly malignant neoplastic entity in young bearded dragons (Pogona vitticeps), gastric neuroendocrine carcinomas, which readily metastasize. Ten bearded dragons with histories of anorexia (8), vomiting (3), hyperglycemia (2), and anemia (3) were included in this study. All animals had neoplastic masses in their stomach, with metastasis to the liver. Microscopically, 6 of these neuroendocrine carcinomas were well-differentiated and 4 were poorly differentiated. For further characterization, immunohistochemistry for protein gene product 9.5, neuron-specific enolase, endorphin, chromogranins A and B, synaptophysin, somatostatin, insulin, glucagon, gastrin, pancreatic polypeptide, and vasoactive intestinal peptide was performed on 5 animals. Because only immunolabeling for somatostatin was consistently observed in all neoplasms, a diagnosis of somatostatinoma was made for these 5 bearded dragons. Some neoplasms also exhibited multihormonal expression. Electron microscopy performed on 1 tumor confirmed the presence of neuroendocrine granules within neoplastic cells. Gastric neuroendocrine carcinomas, and specifically somatostatinomas, have not been previously reported in bearded dragons, or other reptiles, and may be underdiagnosed due to inconsistent, ambiguous clinical signs. In humans, pancreatic somatostatinomas are associated with a syndrome of hypersomatostatinemia, which includes hyperglycemia, weight loss, and anemia, as observed in some of these bearded dragons. Somatostatinomas in humans are commonly associated with neurofibromatosis type 1 (Von Recklinghausen's disease), caused by a mutation in the tumor suppressor gene NF1, which results in decreased expression of neurofibromin. In all 5 animals examined, neoplasms exhibited decreased neurofibromin expression compared with control tissues, suggesting that decreased functional neurofibromin may play a role in the pathogenesis of somatostatinomas in bearded dragons.

Clinical Update on Diagnosis and Management of Disorders of the Digestive System of Reptiles

“…[39][40][41] The majority of these cases were diagnosed as neuroendocrine gastric carcinomas. Clinical signs reported with these gastric carcinomas were unspecific and included anorexia, lethargy, vomiting, and melena.…”

“…Clinical signs reported with these gastric carcinomas were unspecific and included anorexia, lethargy, vomiting, and melena. [39][40][41] The gastric carcinomas were highly malignant, with metastatic spread to liver being reported in most cases. [39][40][41] GI FOREIGN BODIES _________________________ GI foreign bodies have been reported in chelonians and lizards, and to a lesser degree in snakes.…”

“…54-57 Metastatic spread of gastric carcinomas in bearded dragons and pancreatic neoplasia in a monitor lizard have also been reported. 39,41,58 Clinical signs of reptiles with liver disease can be nonspecific (e.g., anorexia) or absent and depend on the underlying hepatic disease process (acute vs chronic). In severe cases of hepatic disease, billiverdinuria, jaundice, and/or diarrhea may be observed.…”

A survey of diseases in captive bearded dragons: a retrospective study of 529 patients

“…The prevalence of neoplasias in lizards in general is between 6% (Hernandez-Divers and Garner 2003) and 8.5% (Garner et al 2004). Case reports about neoplasias in bearded dragons include descriptions of an intrahepatic cholangiocarcinoma, adenocarcinoma and adenomas of the gallbladder (Jakab et al 2011), gastric neuroendocrine carcinomas (Ritter et al 2009;Lyons et al 2010), multicentric benign peripheral nerve sheath tumours (Lemberger et al 2005), a periorbital adenocarcinoma (Darrow et al 2013) and leukaemia (Suedmeyer and Turk 1996;Tocidlowski et al 2001;Garner et al 2004;Gregory et al 2004;Jankowski et al 2011). Neoplasias of the female and male genital tract in bearded dragons were reported by Heckers (2017).…”

Gastrinoma and Zollinger–Ellison syndrome in canids: a literature review and a case in a Mexican gray wolf

“…4,17 The mass was negative for all hormones except for strong multifocal cytoplasmic gastrin immunoreactivity (Fig. 4), which confirmed the neoplastic cells to be gastrin-producing.…”