Immune System Tumors in Dogs

Lymphoma mostly affects middle-aged to senior dogs although some cases have been reported in young puppies, especially Golden Retrievers. Development of lymphoma in young dogs calls into question breeding practices and what can be done to avoid such a heartache. Breeds seemingly most affected by lymphoma are Boxers, Basset Hounds, Rottweilers, Bernese Mountain Dogs, and Golden and Labrador Retrievers.

An immune system tumor in a dog, also called lymphoma, is a common cancer. The lymph nodes and organs such as the spleen or liver are often affected.

In most cases, dogs are not clinically ill when diagnosed with lymphoma. They have been brought to the vet because an abnormal lump is present. Although symptoms vary depending the location and size of the tumor(s.) If tumors are present in the digestive tract vomiting and diarrhea are common. If tumors are present in the chest the dog may have difficulty breathing.

• Loss of appetite
• Weight loss
• Fluid in the abdomen
• Thirst
• Excessive urine production
• Fever
• Swelling of the lymph nodes
• Reddened bumps on the skin or possibly in the mouth

Types

• Multicentric - Affects external lymph nodes and at some point organs
• Mediastinal - Affects the chest
• GastroIntestinal - Can block digestion
• Cutaneous - Originates in the skin
• Extranodal - Rare, can affect many parts including bone
• Central Nervous System - Occurs due to the mastitis of multicentric lymphoma

We still do not understand why some dogs get cancer. When you see dogs develop cancer at a very young age (seen as young as eighteen months!) It is hard to argue against a genetic factor. Giant breed dogs are more prone to bone cancer. Their rapid bone growth in the first two years of life is thought to be a cause of high bone cancer rates in giant breed dogs. Vaccination site cancer happens when the dog is vaccinated year after year in the same spot. To avoid this ensure that your veterinarian changes the location of vaccinations. Consider asking for titer tests to definitively tell if your dog’s vaccinations are in need of renewal. It is speculated that dogs are developing cancer more now because with improved care we’ve eliminated other causes of death. Environmental toxins especially the increased use of lawn pesticides is sometimes thought to be a factor.

Your veterinarian will likely diagnose your dog with a combination of biopsies by fine needle aspiration, serum biochemistry, complete blood count, collection of tissues for cytology, and urinalysis.  A general checkup may reveal signs of illness such as anemia or jaundice. The exact procedure and diagnostic process will depend on the location of the tumor.

Treatment will depend on the age and overall health of your dog. Some people choose not to treat lymphoma in their dog at all. In this case, prednisone can help keep your dog comfortable for his remaining time. Prednisone is not recommended to be used in conjunction with chemotherapy as it can interfere with the effectiveness. Left untreated, dogs generally succumb to cancer within four to six weeks.

The most common form of treatment is chemotherapy. Side effects of chemotherapy are similar to those in humans, vomiting, lack of appetite, weight and hair loss. Remission is achieved in 60-90% of patients. Chemotherapy generally adds several months to a year to the dog’s life.

If the lymphoma is caught early enough and in an accessible place, surgery may be an option. It should be noted that any time an animal is anesthetized there may be complications, however, senior pets seem to have the hardest time to recover, therefore surgery is perhaps not best suited to senior dogs. A young robust dog may undergo surgery, it may take more than one surgery or a combination of surgery and chemotherapy, but in this way a dog can achieve a total cancer free status and live many happy years.

When your dog is undergoing chemotherapy or after surgery or if you decline treatment your dog's appetite will likely decrease. Providing your dog with a fresh home cooked or a raw diet can help encourage him to eat and also bolster his immune system. If you continue to feed kibble adding a topper can help. All grains should be avoided.