Lymphoma in dogs

Lymphoma or lymphosarcoma in dogs is a type of cancer identified by the presence of malignant white blood cells, called lymphocytes, within areas of the body such as bone marrow, the liver and spleen, the lymph nodes, and other areas. It is one of the most common malignant cancers found in dogs, making up as much as 24% of all canine cancer diagnoses within the UK.

What causes lymphoma?

Lymphoma is generally considered to develop in dogs due to a range of genetically inherited risk factors, and so an ancestral history of lymphoma within the bloodline can indicate heightened risk factors for lymphoma development.

There is also limited evidence to suggest that lymphoma may be caused in dogs with no ancestral history of the disease, due to exposure to environmental factors such as toxins and pesticides.

What type of dogs can develop lymphoma?

Any dog that has a family history of lymphoma is at a heightened risk of developing the disease, although the presence of lymphoma within the family tree does not automatically mean that any dog will themselves go on to develop the condition.

Lymphoma development usually begins around the time that a dog reaches middle age, from seven years onwards or slightly younger for some giant breeds, and the risk factors increase exponentially as the dog ages.

Some breeds of dog are considered to have particularly elevated risk factors for lymphoma, including:

• The Basset Hound
• Scottish Terrier
• Bulldog
• Boxer dog
• Bull Mastiff
• Airedale Terrier
• Dachshund
• Pomeranian
• Chow-Chow
• German Shepherd dog
• Rottweiler
• Golden Retriever

While statistics for overall risk by breed are not accurately collated, the Dachshund and Pomeranian are considered to be towards the lower end of the breed-specific risk spectrum, with the Golden Retriever at the high end. It is estimated that as many as one in eight Golden Retrievers will develop lymphoma over the course of their lifetimes.

Types of lymphoma in dogs

Lymphoma in dogs is divided into five classification categories, depending on the severity and pervasiveness of its development, and how advanced it has become.

• Stage one lymphoma is a growth that affects one single lymph node only.
• Stage two lymphoma is known as regional lymphadenopathy, and refers to lymphoma that affects one side of the diaphragm only.
• Stage three lymphoma refers to a generalised enlargement and mutation of all or most of the body’s lymph nodes.
• Stage four lymphoma involves the spleen and liver, and may or may not be accompanied by the enlargement of the lymph nodes at stage two and three also.
• Stage five lymphoma indicated an advanced lymphoma that is affecting the bone marrow, nervous system, and other areas of the body too.

What are the lymph nodes?

The lymph nodes or lymph glands are core components of the immune system, and are distributed throughout the body and linked by channels called lymphatic vessels. Lymph nodes are present in the armpits, neck, stomach, limbs, and many other areas of the body of the dog in different concentrations.

Symptoms of lymphoma in dogs

If your dog is one of the breeds considered to have elevated risk factors for lymphoma, or if you know that there is a history of lymphoma within your dog’s family tree, it is important to know and be aware of the symptoms of lymphoma development, particularly as your dog gets older.

Some of the potential generalised symptoms of lymphoma in dogs to look out for at the early stages include:

• Loss of appetite
• Weight loss
• Generalised recurrent digestive upsets or vomiting
• Elevated temperature or fever
• General lethargy and depression
• Thinning coat or loss of fur
• Increased water consumption and urination
• Enlargement of the lymph nodes, which is usually painless

Lymphoma can affect various different areas of the body, all of which can manifest with a varied range of symptoms. If lymphoma metastasis to the lungs, this can lead to breathing difficulties and coughing, while lymphoma of the digestive system can lead to blood in the stools and a range of other prolonged and pervasive digestive upsets.

As lymphoma can potentially present or metastise to many other areas of the body, including the skin, eyes, nervous system and bone marrow, more specific localised symptoms can vary greatly from case to case. Prompt investigation and differential diagnosis by your veterinarian is vital in any potential or suspected case of lymphoma once initial generalised symptoms have been observed.

How is lymphoma diagnosed?

A range of different methods may be employed by your vet to diagnose lymphoma in the dog, including potentially:

• Tissue biopsy
• Needle aspiration of the lymph nodes
• Blood testing
• Urinalysis
• X-ray
• Ultrasound scan
• Bone marrow biopsy

Treatment and prognosis for dogs with lymphoma

Lymphoma is an aggressive and debilitating cancer, which sadly usually proves fatal. Left untreated, the average survival time of dogs with lymphoma is just two months.

Treatment for lymphoma in dogs is usually palliative, meaning that any pain and other adverse side affects caused by the condition are managed and treated reactively, to improve the standard of living and day-to-day comfort of the affected dog.

Chemotherapy is usually the treatment method of choice for affected dogs where treatment is considered to be a viable option, and chemotherapy may eliminate localised stage one lymphomas entirely, and slow the progression of other forms of the disease. However, lymphoma is an aggressive cancer that generally recurs even when initially treated successfully, and a full and final cure for lymphoma in the dog is generally not considered possible.

Nevertheless, treatment with chemotherapy if recommended by your vet can potentially add a couple of years or even longer to your dog’s life, and give them a good and comfortable standard of living during that time. The earlier that treatment is sought and begun, the greater the chance that your dog will have of living comfortably and in reasonably good health with you for some time to come.