No one ever wants to hear that their cat has cancer. Fortunately, stomach cancer is very rare in cats, representing less than 1 percent of all cancers in cats (1). Unfortunately, the symptoms of stomach cancer in cats are common to many types of illness, ranging from minor to serious. 

Let’s take a closer look at the causes and signs of cat stomach cancer and how to treat this condition.

What is Cat Stomach Cancer?

Stomach cancer refers to abnormal growth of cells or tissue within the stomach. The medical term is gastric neoplasia. The types of cancer that develop in other organs of the body can also develop in the stomach. The most common type of stomach cancer in cats is lymphoma (lymphosarcoma). It can be part of generalized (diffuse) gastrointestinal lymphoma, which is a much more common form of cancer in cats, or it can be found on its own. 

Other more rare types of gastric cancer in cats include gastric adenocarcinoma, leiomyoma, leiomyosarcoma, gastrointestinal stromal tumor, adenoma, mast cell tumor, carcinoma, extramedullary plasmacytoma, and other sarcomas. The name of the cancer has to do with the type of cells the cancer originated from.

There are no risks associated with breed or sex. There are no known genetic risk factors for gastric neoplasia in cats. The average age at diagnosis is greater than 12 years (2).

Causes of Stomach Cancer in Cats

The cause of stomach cancer in cats is generally unknown. Cats who have gastrointestinal lymphoma are more likely to develop gastric lymphoma as the disease spreads. Similarly, inflammatory bowel disease (IBD) can become gastric or gastrointestinal lymphoma over time. Although there are lifestyle choices including diet and exercise that are known to affect risk of gastric neoplasia in humans, similar associations have not been found in cats.

Stomach Cancer in Cats Symptoms

The symptoms of stomach cancer in cats tend to be the same group of symptoms cats exhibit for a long list of other illnesses and diseases that range from mild to severe. These include:

• Vomiting
• Diarrhea
• Not eating (anorexia or inappetence)
• Weight loss
• Lethargy
• Changes in behavior (hiding, not seeking out attention, etc.)

These are also the symptoms of inflammation or infection of the stomach or intestines, parasites, and other illnesses such as endocrine and metabolic disease. If there is ulceration of the gastric tumor, there may be blood in the vomit or the stool may be dark and tarry (melena). 

Stomach cancer in humans is painful and so it is assumed that the condition is also painful in cats. Cats may show their pain by not eating, having less energy, and being less social or hiding.

Cat Stomach Cancer Stages and Progression 

Cancer is often described in stages based on the spread of the cancer to other locations in the body and whether the pet is ill at the time of diagnosis. Cancer can also be described in grades based on the aggressiveness of the tumor on the local tissue, likelihood of spread, likelihood of recurrence after surgery or chemotherapy, and consequences of its presence. The stage and grade of a cancer are not specific to its original location, such as the stomach, but rather depend on the type of cancer it is. 

In the case of gastric lymphoma, the most common type of stomach cancer in cats, it is most often high-grade, meaning aggressive and less likely to fully respond to chemotherapy. Since risk factors for its development include other gastrointestinal inflammation or cancer, gastric lymphoma is most often late-stage by the time of diagnosis, having spread from or to other tissues in the body. 

Diagnosing Feline Stomach Cancer

The first step in diagnosing any disease in a cat is a physical exam. This involves a detailed examination of all parts of the cat’s body to assess for abnormalities. Most often the physical exam is normal or non-specific for cats with symptoms of stomach cancer. Non-specific exam findings include evidence of dehydration, weight loss, pale gums, and/or lethargy. It is rare for a veterinarian to be able to feel stomach cancer on abdominal palpation in cats.

The next important step in diagnosis is blood work. A cat with stomach cancer may have anemia, elevated blood nitrogen levels, low protein, or their blood work could be normal. Next, abdominal ultrasound can be useful in finding a tumor or abnormalities of the tissues of the stomach. Sometimes a small needle sample (aspirate) can be taken at the time of the ultrasound and analyzed under a microscope for the presence of cancer cells. Abdominal ultrasound has the advantage of assessing all of the abdominal organs for evidence of cancer spread (metastasis). Alternatively, gastroscopy can be performed where a tiny camera is inserted into the stomach to visually examine the tissue and a biopsy sample can be taken. Occasionally, exploratory abdominal surgery will be required to diagnose stomach cancer in cats. 

X-rays are not usually diagnostic for stomach cancer, although the addition of contrast material can outline a mass if there is one. They may be part of the diagnostic testing work-up for cats with gastrointestinal symptoms, so it is not wrong for your veterinarian to recommend them. While the X-rays are not likely to show cancer, they are helpful in eliminating other possible causes of your cat’s symptoms.

Cat Stomach Cancer Treatment Options

Treatment options for cats with stomach cancer include surgery and chemotherapy. Most often surgery will be performed first to remove the bulk of the mass and then chemotherapy will be used to treat any cancer left behind or any cancer that has already metastasized. Some types of cancer, such as lymphoma, may be treated with chemotherapy only. 

Cost to Treat Stomach Cancer in Cats

Specific costs depend on the types of treatment(s) recommended for your cat. Initial diagnostic tests may be in the range of $1,000-3,000, depending on which tests are performed. Abdominal ultrasound is less expensive than gastroscopy. Surgery to remove gastric neoplasia should be performed by a board-certified veterinary surgeon and will cost $4,000-$7,000, depending on the specific type of surgery required. A round of chemotherapy is in the range of $3,500 to $6,000.

Prognosis for Stomach Cancer in Cats

Without treatment, a cat will die from the cancer or its side effects within about one month. Specific prognosis with treatment depends on the type of cancer. Gastric lymphoma, for example, has a survival of 6-18 months, depending on response to chemotherapy. Stomach cancer is a very serious disease in cats and in general, the long-term prognosis is poor.

There is no way to prevent stomach cancer in cats.