What are these tumors?
Tumors of the epithelial, glandular stomach lining include non-cancerous polyps and some types of chronic (hyperplastic) gastritis. Malignant epithelial tumors (gastric adenocarcinomas) cause progressive illness. This usually starts only a few weeks before diagnosis but within that time, they have usually spread locally and to distant organs. Many recur following surgery.
What do we know about the cause?
The reason why a particular pet may develop this, or any cancer, is not straightforward. Cancer is often seemingly the culmination of a series of circumstances that come together for the unfortunate individual.
In people, the bacterium Helicobacter pylori is the cause of a spectrum of disease. This includes promoting the development of gastric adenocarcinoma. We do not know whether the same is true in dogs, which also carry Helicobacter bacteria. Certain foods are implicated in these cancers in both people and farm animals and chemicals such as nitrosamines have been shown to induce gastric adenocarcinomas.
Why has my dog developed this cancer?
Some animals have a greater tendency (genetic susceptibility) to cancer. Some breeds have far more cancers than others, often of specific types. The more divisions a cell undergoes, the more probable is a mutation so cancer is more common in older animals.
Are these common tumors?
Benign stomach tumors are very rare. Malignant epithelial or glandular tumors (adenocarcinomas) occur more frequently, but are still uncommon in dogs.
How will these cancers affect my dog?
Vomiting, often not associated with food intake, and sometimes containing blood, occurs in almost all animals with gastric tumors. Other clinical signs are weight loss, loss of appetite, diarrhea and blood in the feces.
How are these cancers diagnosed?
Cancer is often suspected from the clinical signs. X-rays may be useful in detecting the tumors. Blood tests are not diagnostic but sometimes indicate if the tumor is bleeding internally. In order to identify the tumor, it is necessary to obtain a sample of the tumor itself. Various degrees of surgical invasion may be needed such as endoscopy and exploratory surgery. The tissue samples are submitted for microscopic examination. Biopsies taken with the aid of an endoscope are rarely diagnostic for cancer and examination of a larger surgical specimen from deeper tissue is usually needed. The histopathology (microscopic examination of specially prepared and stained tissue sections) is done at a specialized laboratory where the slides are examined by a veterinary pathologist.
What types of treatment are available?
Treatment is surgical removal of the tumor.
Can these cancers disappear without treatment?
Cancer rarely disappears without treatment but as development is a multi-step process, it may stop at some stages, particularly if a promoting agent such as Helicobacter infection is removed. The body’s own immune system can kill cancer cells but it is rarely 100% effective. Rarely, loss of blood supply to a cancer will make it die but the dead tissue will probably need surgical removal.
How can I nurse my dog?
After surgery, the operation site needs to be kept clean and your pet should not be allowed to interfere with the site. Any loss of sutures or significant swelling or bleeding should be reported to your veterinarian.
Your pet may require a special diet and you may be asked to check that your pet can pass urine and feces or to give treatment to facilitate this.
How will I know how the cancer will behave?
Histopathology will give your veterinarian the diagnosis that helps to indicate how it is likely to behave. The veterinary pathologist usually adds a prognosis that describes the probability of local recurrence or metastasis (distant spread).
When will I know if the cancer is permanently cured?
’Cured’ has to be a guarded term in dealing with any cancer.
Gastric polyps are usually cured by surgical removal. They are thought to be non-precancerous (not capable of becoming cancer). Despite early diagnosis (often only weeks since illness was noted), most gastric adenocarcinomas are unfortunately already spreading locally at the time of surgery. Surgical removal is therefore difficult. They can also spread within the inside lining of the abdomen (peritoneum) and to many different parts of the body including the lungs. Despite this, post-surgical survival times have increased recently, rising from a few months to between one and three years.
Are there any risks to my family or other pets?
No, these are not transmitted from pet to pet or from pets to people.
Based on material written by Joan Rest, BVSc, PhD, MRCPath, MRCVS. and modified with permission from Lifelearn Inc.
© Copyright 2004 Lifelearn Inc.
