Gastric Neuroendocrine Carcinoma in a Dog
164
The dog was euthanized two months after the diagnosis
was made due to deterioration of the general condition
and the poor prognosis. Unfortunately the body was not
submitted to post mortem examination.
4. Discussion
Gastric tumours are rare in domestic animals and gastric
NETs have only been reported in dogs to date [2]. Ac-
cording to the Veterinary WHO classification of tumours
of the alimentary tract, NET of the stomach (also called
carcinoid or neuroendocrine carcinoma, NEC) are de-
fined as low-grade malignant tumours with neurosecre-
tory granules that are identifiable light microscopically,
immunohistochemically using special stains, or by elec-
tron microscopy [2,6,7].
Well differentiated NETs cannot simply be classified
by conventional histopathology with respect to their
growth pattern and cellular features [1]. According to the
human WHO classification, a gastric NEN larger than 2
cm, invading the T. muscularis is considered a well dif-
ferentiated low-grade NEC. Tumours up to 2 cm, con-
fined to the mucosa-submucosa with or without angioin-
vasion are classified as benign or low-grade NET and
poorly differentiated NEC are high-grade malignant [8].
There are few case reports on gastric NETs in dogs. A
gastric carcinoid was reported in a 13-year-old female
whippet that was presented with a 10-day history of
weakness and ataxia as well as was vomiting for 3 days.
Post mortem examination showed a 3.5 cm-diameter
erosive transmural lesion on the antral mucosa of the
stomach. Histologically, the tumour was described as a
poorly differentiated NEC with high mitotic rate, multi-
focal necrosis and invasion of blood and lymphatic ves-
sels. Metastases were observed in liver, spleen, kidney,
lungs, lymph nodes and brain [9,10]. More recently, gas-
tric carcinoids were reported in the Norwegian Lunde-
hund, a breed often afflicted by chronic atrophic gastritis
(CAG) and gastric tumours, including gastric carcinoma
and NEC [11,12]. The Lundehund is thought to develop
hyperplasia of gastric endocrine cells in response to de-
creased acid secretion and hypergastrinaemia, related to
CAG [11]. Four of eight gastric tumour-bearing Lunde-
hund exhibited gastric carcinoids, with metastases into
regional lymph nodes. Three animals showed liver me-
tastases, and in one dog, lung metastases were demon-
strated. An association of chronic atrophic gastritis and
gastric tumours is also described in humans that develop
type 1 gastric NET as a result of increased gastrin pro-
duction [1] .
Male dogs seem predisposed to developing gastric tu-
mours, and the dog in the present study as well as three
of four affected Norwegian Lundehund were reported to
be male [6,11]. In humans, male predominance is re-
ported for sporadic (type 3) NET and undifferentiated
gastric carcinoma (type 4 NET) [1].
Immunohistochemically, NET cells stain positive for
chromogranin, synaptophysin, NCAM/CD56 and may be
positive for a variety of peptide hormones (e.g. ACTH,
calcitonin) and biogenic amines (e.g. serotonin) [1,3,13].
Likewise, the tumour in the present study was positive
for chromogranin A, synaptophysin and cytokeratin, and
the tumour of the female whippet, in contrast to the pre-
sent case, was additionally positive for NSE [9]. In the
Lundehund, gastric NET was confirmed by chromo-
granin A and synaptophysin immunohistochemistry [11].
Metastases were found in all reported cases. In the pre-
sent study only the biopsy specimen of the lymph node
showed metastases, however, due to the small size of
pancreatic and liver biopsies that were taken during
laparoscopy, we can not exclude distant metastases that
may have been overlooked. The invasive growth and
invasion of blood vessels however makes distant metas-
tases likely and argues for malignant behaviour. The mi-
totic index of the gastric NET identified in the present
report was fairly low (2 - 20 per 2 mm2), which is com-
parable to the mitotic index of gastric NET in the Lun-
dehund but sligh tly lower than that of the female whip pet
[9,11]. According to the human and veterinary diagnostic
criteria, the present case of a gastric NET would be des-
ignated as a well-differentiated intermediate-grade (G2)
maligna nt NET/NEC.
5. Acknowledgements
We thank Elisabeth Kemper and Karin Stingl for excel-
lent technical assistance
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