Gastric neoplasia is rare in dogs and cats compared with man. The types of tumour detected in small animals include polyps, adenomas, leiomyomas, adenocarcinomas and lymphosarcomas. The most frequent tumour in dogs is the adenocarcinoma and the most frequent site is the antrum or pylorus of the stomach. Lymphosarcoma is the commonest feline tumour although this is not frequently seen. Tumours frequently ulcerate so symptomatology may be similar to that observed with gastric ulceration, and endoscopically they appear very similar so histopathology of surgical biopsy is essential to differentiate which is present. Tumours have been observed more frequently in Rough Collies, Irish Setter and Terrier breeds, the mean age being 10 years and possibly more common in males than females ().
Classically there is a history of chronic vomiting, polydipsia and weight loss. The signs may appear over a short period of time or may develop more slowly over many months. The vomitus may be gastric juice and saliva or may contain food. There is no strong correlation between eating and vomiting but it certainly occurs in some individuals. Vomitus may also contain fresh or changed blood (coffee grounds) but this is not pathognomonic of gastric tumours. The animals frequently salivate and become anorexic and depressed in the latter stages of the condition.
A diagnosis cannot be made from clinical findings alone but usually requires confirmation from radiography, endoscopy or exploratory laparotomy. Tumours are most frequently found in the pyloric antrum or along the lesser curvature to the cardia. Plain X-rays usually fail to reveal the tumour but may show roughening of the surface or narrowing of the pyloric lumen. Contrast studies may reveal filling defects and delayed gastric emptying but these changes are not a common feature. Endoscopy and biopsy is required to obtain a definitive diagnosis (7 and Plate 3). Usually there are macroscopic changes present including ulceration, hypertrophy of the mucosa or outflow obstruction. Multiple ulcers are more frequently observed in lymphosarcoma while single large ulcers occur more frequently with adenocarcinomas. The periphery of the lesion should be biopsied and more than one sample must be collected. Adenocarcinoma frequently invades and produces a scirrhous or fibrosing reaction which results in an inflexible area of the gastric wall with distended lymphatics and early neoplastic peritonitis with adhesions. Changes may not be picked up by endoscopy and biopsy sampling if the mucosa is not involved. In such cases where no mucosal changes can be readily observed, it would be important to consider exploratory laparotomy. Although endoscopy may miss some forms of tumour, laparotomy will always allow a diagnosis to be made. However it is a very invasive technique to be employed routinely whenever a gastric condition is suspected ().
Gastric neoplasia: Treatment
The prognosis must be very guarded. Surgical resection may be successful when the tumour is confined to a small area of the stomach. However the tumour is often well-established, locally spreading and may have metastasized by the time a diagnosis is obtained, necessitating euthanasia. Chemotherapy combined with surgery may be a possibility in the future but is rarely considered at the present time.
Selections from the book: “Digestive Disease in the Dog and Cat” (1991)