Lymphoma in dogs

Cancer. It’s a scary word and not one you ever want to hear. But the reality is that your dog could develop cancer at some point during their life.

One of the most common cancers in dogs is lymphoma. Lymphoma is a cancer of lymphocytes, a type of white blood cell. White blood cells protect the body against illness and disease. Lymphoma is most commonly found in the lymph nodes (glands) but it can also affect the liver, spleen, bone marrow, thymus, kidneys, digestive system, and skin. While chemotherapy can put lymphoma into remission for some dogs, unfortunately, it is rarely cured.

Sadly, one of the Just For Friends team, Bella was diagnosed with Lymphoma in September 2022. Within two days of receiving her test results she was referred to The Queens Veterinary School Hospital, Cambridge.

What Is Canine Lymphoma?

Canine lymphoma, also called lymphosarcoma, is a type of cancer that affects parts of the immune system (e.g., lymph nodes, bone marrow, spleen, thymus and others). The Merck Veterinary Manual explains that lymphoma develops from the uncontrolled and pathological clonal expansion (replication) of B-cells or T-cells (also called lymphocytes). B lymphocytes and T lymphocytes are types of white blood cells that are involved in the body’s immune response.

There are multiple forms of canine lymphoma that affect different areas of the body. The four main forms are described below:

  • Multicentric (systemic): This is the form diagnosed in most dogs and affects lymph nodes throughout the body.
  • Alimentary: This is the second most common form (but has a much lower incidence than multicentric lymphoma) and affects the gastrointestinal tract.
  • Mediastinal: This is a rare form involving the thymus and/or lymph nodes of the chest and affects the respiratory system.
  • Extranodal: This is another rare form that affects organs outside the lymphatic system (commonly the skin but also the eyes, liver, nervous system or other organs).

Why Do Dogs Develop Lymphoma?

It’s unclear why some dogs develop lymphoma, but it’s thought to be due to a combination of factors. While any dog can develop lymphoma, there is possibly a genetic link since some breeds are more susceptible to developing it than others (e.g., golden retriever, basset hound, Saint Bernard, Scottish terrier, Rottweiler). It’s also more common in dogs who are middle-aged or older.

What Does Lymphoma Look Like in Dogs?

Lymphoma symptoms can often mimic symptoms of other diseases. For example, a dog with lymphoma can have:

Possible symptoms include:

  • Lumps under the jaw or elsewhere on the body (see picture below) which are big, swollen lymph nodes
  • Reduced appetite
  • Drinking and peeing more than usual
  • Low energy
  • Weight loss
  • Vomiting
  • Diarrhoea or constipation
  • Pale gums
  • Yellow gums (jaundice)
  • Breathing problems and/or coughing
  • Lumps in or under the skin or skin that is crusting, scaly, or ulcerated along with hair loss

 Swollen lymph nodes, but a swollen lymph node doesn’t mean a dog has lymphoma. Lymph nodes can also swell due to an infection or another disease.

Dogs with multicentric lymphoma have swollen lymph nodes that aren’t painful. For other forms or advanced stages of lymphoma, the symptoms vary depending on the organs affected.

If you find a lump on your dog, you shouldn’t immediately think, “Oh no, it’s lymphoma.” It may not be a lymph node and it may not be cancerous. Always ask your veterinarian for advice if you are concerned about a lump, especially if your dog also has other symptoms — it may be nothing, but it could be something serious.

Diagnosing and Treating Canine Lymphoma

If your veterinarian suspects lymphoma, they will often start the diagnostic process by examining cells from an affected lymph node or organ. During this process, the veterinarian uses a fine needle to aspirate (draw out) a small number of cells to look for cancerous cells under a microscope. They may also do a biopsy (surgical removal of tissue) and look at the tissue under a microscope, run blood work to check blood counts and organ function, or use other diagnostic tests. If your dog does have lymphoma, they may suggest performing tests that help determine which stage (I to V) it is at, which helps guide them on treatment options.

If appropriate for the patient and financially possible for pet parents, chemotherapy is the most effective method to treat canine lymphoma.

Chemotherapy drugs attack and kill cancer cells. The aim of using chemotherapy is to ensure a good quality of life and achieve remission (when the disease is not completely gone but we cannot detect it) – but it is unlikely to be a complete cure.

In some cases, chemotherapy can extend your dog’s lifespan from a few months to a year or more. Some types of lymphoma respond very well to chemotherapy and many dogs tolerate having chemotherapy very well with minimal to no side effects.

However, response varies a lot, and it is important to know that each case of lymphoma is different, and every dog will respond differently. Unfortunately, some types of lymphoma don’t respond well to chemotherapy. Even if your dog responds well, they are very unlikely to be cured completely. They may go into remission for a period of time and live longer than they would have done without treatment, but eventually their cancer will return. It is also important to consider how your dog will cope with chemotherapy, as it usually involves multiple visits to your vet, often with blood tests and injections, which some dogs may find stressful. Your vet may refer you to a specialist referral centre.

It’s important throughout chemotherapy that your dog’s quality of life is good. Treatment usually involves combining different types of drugs which may be an injection, tablets or a combination of both. It’s often given over a long period of time for example up to six months. The cancer can eventually become resistant to treatment which means it comes back again. While chemotherapy can have side effects, in dogs these tend to be mild. Your vet will discuss any potential side effects linked to the specific medication your dog is on.

If you’re worried about chemotherapy side effects, it’s encouraging to note that there are typically fewer side effects for dogs undergoing chemotherapy compared with humans. Chemotherapy can help dogs with lymphoma go into remission, but the vast majority of dogs will relapse. Other treatments are available, but they are usually less effective.

According to the Merck Veterinary Manual, dogs who don’t receive treatment usually live for about four to six weeks. If dogs receive multidrug chemotherapy, the median (middle of the range) survival time increases to around 12 months for dogs with B-cell lymphoma and around six to eight months for dogs with T-cell lymphoma. Keep in mind that the treatment response and survival time varies between dogs. Sadly, it is very rare for dogs with lymphoma to be cured.

Canine lymphoma is a heartbreaking diagnosis for any pet parent, and we hope that you and your dog never have to experience it. At the time of publishing Bella is still enjoying her days in the office next to the wood stove,

Article by Just For Friends,