What is it, how is it treated and what is the prognosis?

What is lymphoma?

Lymphoma is a term used to describe a range of cancers that affect the immune system or more specifically the lymphocytes – a type of white blood cell. These white blood cells help to protect the body from infection and support the proper function of the immune system by preventing the spread of disease or viruses throughout the body. Lymphoma occurs when there is a genetic mutation, or a series of mutations, within a lymphocyte, causing the cells to abnormally grow and become malignant.

What causes lymphoma in dogs?

While the most common cancer to be diagnosed in dogs, the exact cause of canine lymphoma is unknown and could be caused by a number of issues such as bacteria, infection, chemical exposure or physical factors such as magnetic fields. The condition is also more common in middle-aged and older dogs, and research has shown that there is likely to be a genetic predisposition in certain larger dog breeds such as basset hounds, German shepherds, Irish wolfhounds and rottweilers.

What are the different types of lymphoma?

There are more than 40 different known types of known canine lymphomas, and survival rates, symptoms and the aggressiveness of the disease vary depending on the type. The four most common types of canine lymphoma are:

  • Multicentric lymphoma: This is the most common type of canine lymphoma and is cited as the diagnosis in around 80% of canine lymphoma patients. It is found in the lymph nodes and can affect multiple nodes at once. It can also affect the liver, spleen, or bone marrow.

    There are a number of peripheral lymph nodes located close to the skin’s surface, which you’ll be able to feel if they become enlarged. These are located in front of the shoulder, behind the knee, in the armpit and in the groin.

  • Alimentary lymphoma: The second most common lymphoma in dogs, alimentary lymphoma affects the stomach and intestines.
  • Mediastinal lymphoma: This type of lymphoma affects the organs in the chest such as the lymph nodes or thymus.
  • Extranodal lymphoma: Extranodal lymphoma affects a specific organ, such as the skin, lungs, kidneys or central nervous system.


Stages of lymphoma

Canine lymphoma is categorised by stages depending on its invasiveness and how it metastases. The stages are:

  • Stage 1 when only one lymph node is affected. 
  • Stage 2 when only one side of the diaphragm is affected.
  • Stage 3  is generalised lymphadenopathy, which happens when the lymph nodes are enlarged.
  • Stage 4 when the liver or spleen is enlarged.
  • Stage 5 when lymphoma affects bone marrow, the central nervous system or other organs. 

What are the symptoms of canine lymphoma?

The symptoms of canine lymphoma depend entirely on which part of the body is affected by the disease. In dogs presenting with multicentric lymphoma, swelling of the lymph nodes in the neck, shoulders, armpit, groin or behind the knee is often the first sign of the disease. In less common cases of lymphoma such as extranodal lymphoma or mediastinal lymphoma, clinical signs will differ depending on the affected area of the body.

Most dogs with lymphoma are not in obvious pain, and may not even appear to be ill. But, if left untreated, the disease can, over time, cause a range of illnesses and clinical symptoms such as:

  • weight loss
  • vomiting
  • fever
  • loss of bowel control
  • loss of appetite
  • increased thirst
  • loss of hair or fur
  • general weakness
  • lethargy
  • abnormal behaviour
  • shortness of breath

It’s important to remember that, if you are a dog owner and you feel the presence of any new lumps, you should contact a veterinary professional as soon as possible. 

How is it diagnosed?

A rapidly progressive disease, lymphoma quickly spreads throughout the body, so it’s important to get your dog checked out by a veterinary professional as soon as possible if you suspect that they may be suffering from the disease. However, it’s important to note that, if your dog has enlarged lymph nodes it doesn’t necessarily mean that they have lymphoma, and there are a number of other conditions that may present with the same clinical signs such as bacterial, viral, parasitic or fungal infections or other cancers.

To determine whether or not your dog has lymphoma, your veterinarian will need to assess the extent of the disease and determine a suitable treatment. First, a thorough physical examination will be completed, including a full medical history check to rule out any pre-existing conditions. Similarly, a full blood count, urine analysis may also be needed to gain a clearer picture of the problem. As symptoms are similar to those of other infections, your vet may need a full travel history too.

In order to accurately diagnose the disease, a sample of the enlarged lymph node or affected organ will need to be taken, either by fine needle aspirate or tissue biopsy. Fine needle aspiration is a simple procedure during which a thin needle is used to collect an aspirate of cells, and causes minimal discomfort to your pet. A tissue biopsy may also be needed. but this procedure usually takes place under general anaesthesia. The cell or tissue samples will then be sent to a pathologist to evaluate and assess. 

An X-ray or ultrasound scan will be performed to gain a clearer picture of organs and internal lymph nodes, while certain cases will require a bone marrow sample to check for the presence of cancerous cells.


Can lymphoma be treated?

While it is rare for dogs to recover fully from lymphoma, the most successful treatment is chemotherapy, which is normally administered via weekly injections and oral drugs., however, specific treatments will vary on a case by case basis.

A steroid called prednisone can be used if chemotherapy is not an option, however this does not treat the cancer, but simply helps to reduce symptoms and manage the disease. It’s important to note that prednisone will only help your dog to survive for up to 3 months, and can make the cells resistant to chemotherapy, making treatment less successful if you change your mind further down the line.

How to care for a dog receiving chemotherapy for lymphoma

While most dogs do not react to chemotherapy and lower, more frequent doses of the drug are given to pets in order to minimise side effects, some may still experience a range of symptoms during the course of treatment. These include:

  • nausea
  • diarrhoea
  • lethargy
  • decreased appetite

Your dog’s appetite is likely to vary while receiving chemotherapy and so you should take advantage of times when your pet is hungry, as they will need to keep their strength up to fight the disease. It’s important to remember, however, that you shouldn’t force your dog to eat if they don’t want to, nor introduce any new foods into their diet during this time.

What is the life expectancy of a dog with lymphoma?

The life expectancy of a dog with lymphoma depends entirely on the stage, the type of lymphoma and response to treatment. However, if your dog is not treated, they have an expected survival rate of around 4-6 weeks. While only a small number of dogs with lymphoma are cured of the disease, a wide range of cases are put into remission with chemotherapy and drug treatments but, unfortunately, the majority of dogs suffering from lymphoma will eventually die from related causes.

We understand that a visit to the vet can be stressful, which is why we offer a different calibre of care and support each and every pet and owner we see. Not only are we equipped and experienced in offering advanced treatments for a range of conditions and illnesses, but we’ll also be alongside you throughout the referral process.

If you’re a veterinarian looking to make a referral, get in touch with us today