Stomach and Intestinal Cancer in Cats

Types of gastrointestinal cancers include adenocarcinoma, leiomyosarcoma, lymphoma, and mast cell tumors. Older cats have a predisposition for developing gastrointestinal cancers. Feline leukemia virus and immunodeficiency virus may also play a role in the development of gastrointestinal cancer.

Stomach and intestinal cancer is a rare type of feline cancer, accounting for less than one percent of all reported cancers in cats. Gastrointestinal cancers are most commonly found in the small intestine. Stomach and intestinal tumors can be benign, but are typically malignant and aggressive. 

Cats suffering from stomach or intestinal cancer will almost always show changes in eating habits due to tumors in the gastrointestinal tract. Stomach and intestinal cancers are serious conditions that require early detection for the best prognosis. If your cat is exhibiting any of the following symptoms, seek immediate veterinary attention:

• Changes in behavior
• Lethargy
• Loss of appetite
• Vomiting
• Diarrhea
• Blood present in vomit or feces
• Weight loss
• Depression
• Difficulty defecating
• Abdominal pain or swelling
• Signs of abdominal infection
• Masses in the abdomen
• Pale gums or other signs of anemia

Types

Adenocarcinoma

Adenocarcinomas located in the digestive system usually affect the large and small intestines. This type of gastric cancer is extremely rare in cats and doesn’t usually affect the stomach. Adenocarcinomas grow rapidly, tend to be aggressive during metastasis, and may cause blockages in part of the intestines.

Leiomyosarcoma

This type of tumor can be benign or malignant and originates within the smooth muscle. Leiomyosarcoma can occur in any part of the body, but most commonly affects the gastrointestinal tract. Malignant leiomyosarcomas have a high metastatic rate and typically spread to the lymph nodes and liver.

Lymphoma

Lymphoma is a type of aggressive malignant cancer that originates from an uncontrolled growth of lymphocytes. Lymphocytes are a type of white blood cell that protects the cat from foreign bodies or substances that may cause disease. Lymphoma can affect any part of the body, but is most commonly found in the gastrointestinal tract. Lymphoma is the most common type of gastric cancer in cats.

Mast Cell Tumors

Mast cells, like lymphocytes, are a type of white blood cell. While mast cell tumors typically form on the skin, they may also affect the gastrointestinal tract. Bleeding ulcers may be symptomatic of mast cell tumors, and Siamese cats in particular have a predisposition to developing mast cell tumors.

The cause of stomach and intestinal cancer in cats will depend on the type of cancer and where it originated. As with most types of cancer anywhere in the body, gastrointestinal cancers are caused when cells begin to grow at an uncontrolled rate. Lymphoma, in particular, may be caused by a previous bout of feline leukemia virus (FeLV) or the immunodeficiency virus. The link, however, is not fully understood by researchers.

The vet can make a tentative diagnosis based on presentation of symptoms and a physical examination. Be sure to inform the vet of the duration and extent of your cat’s symptoms, as well as any previous stomach or intestinal problems. An x-ray and a biopsy of the abdominal tissue will be required for a definitive diagnosis. The vet may also conduct other forms of standard testing to assess whether the cancer has spread. In some cases, the vet may perform a gastroscopy, which will require anesthetic.

Treatment will depend on the type and stage of the cancer. Surgery is required for most types of gastrointestinal cancers, apart from lymphoma. Gastrointestinal lymphoma may be partially treated through surgery, but will typically require chemotherapy to ensure the best prognosis possible. 

Before surgery, your vet will run some standard tests, including a blood chemistry profile, blood count, and urinalysis. They may also perform additional x-rays to ensure the cancer hasn’t spread to other organs. The surgery itself will usually involve the partial removal of the stomach and/or affected intestine. The veterinary surgeon will then reconnect the stomach to the intestine. Since radiation therapy can harm nearby organs, this is not usually recommended for most cases of gastrointestinal cancer.

Your cat will typically be hospitalized for two days following surgery, and will receive intravenous fluid therapy during this recovery period. Your vet may prescribe anti-vomiting and pain management medication, as well as antacids to prevent stomach ulcers. 

On the return home, ensure that your cat has a warm, secure place to rest. You’ll need to limit activity for up to three weeks to allow for adequate recovery, and don’t allow the cat to irritate the surgery site. If you notice any bleeding, swelling, or irritation of the surgery site, contact your vet immediately.

If your cat requires chemotherapy – which will be recommended for most malignant tumors – the vet will schedule follow-up appointments to administer chemotherapeutic drugs via injection. These treatments will begin two weeks after surgery and will occur once every two to three weeks for up to five sessions.

Prognosis will depend on the aggressiveness and stage of the cancer at the time of operation, as well as the success of the operation itself. Surgery may be completely curative for benign tumors. Malignant gastrointestinal cancers tend to have a poorer prognosis and a higher recurrence rate.