In general, a blood test and normal radiography are not sufficient to make a diagnosis.
Generally, the blood test does not show specific evidence for gastric adenocarcinoma. It may help to detect certain side effects or to distinguish them from other tumour types.
By contrast radiography of the stomach, a growth that should not be present in the stomach can be discovered. It is also possible to find a stomach ulcer, which often occurs with gastric adenocarcinomas. Alternatively, the stomach may empty more slowly than usual (the contrast material moves more slowly than usual).
Via an ultrasound the veterinarian can collect a sample from more difficult to reach places with a needle. The location of the tumour may be a possible indicator of the tumour type. Gastric adenocarcinomas tend to occur more at the level of the gastric outlet, while leiomyosarcomas are more common at the level of the stomach entrance.
By sliding a flexible tube into the stomach of the dog, the veterinarian can visualize growths and take extensive samples in a targeted manner. As the surface of a gastric tumour can be superficially necrotic, inflamed or ulcerated, it might be necessary to take several larger tissue samples. This is not always possible via the endoscopic tube and may require surgery.
This is the surest way to obtain a good sample of the tumour.
Thanks to these investigations, it can be determined whether the tumour is malignant or very aggressive. This information will help determine if additional treatments are needed.
If there is a suspicion of a GIST (gastrointestinal stromal tumour), a CD117 staining is done to confirm this. This is a rare tumour that arises from the support tissue of the gastrointestinal tract.