Lymphoma in Dogs

What is lymphoma?

Lymphoma, also known as a lymphosarcoma or LSA, is caused by a cancerous proliferation of lymphocytes, or white blood cells that normally function in the immune system. It is one of the most common tumors seen in dogs. It affects dogs of any breed and age, although most are middle-aged or older when diagnosed. Golden retrievers are considered a breed at increased risk of developing a lymphosarcoma. The cause of these tumors is not known.

What are some of the signs my dog has lymphoma?

The most common form of lymphoma causes a non-painful enlargement of one or more lymph nodes that can be seen or felt on the surface of the body. Occasionally, a lymph node becomes large enough to impair function (obstruction of blood flow or airway, for example).

Other forms can involve the liver, spleen, bone marrow, gastrointestinal tract, skin, nervous system, and other organs. The clinical signs will reflect the organ system involved. For instance, dogs with gastrointestinal forms may vomit or have diarrhea. Many dogs will simply feel ill, lose their appetite, or become lethargic.

In some cases, the tumor is an incidental finding when an otherwise healthy appearing dog is seen by a veterinarian for an unrelated reason.

If you notice fast growing lumps on your dog that seem to be in the area of the major joints (at the neck, in front of the shoulders, in the armpits, at the back of the knees or in the groin) have it examined by a veterinarian, even if the animal feels well.

How is lymphoma diagnosed?

Lymphoma is often diagnosed with a biopsy, a minor surgical procedure to remove a piece of a lymph node or other organ that may be affected by cancer. Since lymphoma can spread to almost any tissue in the body, a thorough work-up needs to be done to determine the stage of disease.

Staging can involve aspiration of one or more lymph nodes, thoracic and abdominal radiographs, ultrasound (to look for big nodes in the abdomen and to look at the liver and spleen), or bone marrow examination. Often, obtaining blood for a complete blood count and biochemical profile, and a urinalysis will be advised, as these can help assess overall health and provide information that potentially influences treatment recommendations.

Lymphoma is categorized into five stages, depending on the extent of the disease in the body:

  • Stage I – single lymph node enlarged 
  • Stage II – multiple nodes enlarged on either the front half or back half of the body 
  • Stage III – multiple nodes enlarged on both front and back halves of body 
  • Stage IV – involvement of the liver and/or spleen 
  • Stage V – bone marrow involvement, or involvement of other organs (e.g. gastrointestinal, skin, nervous system) 

Each numbered stage can be further divided into two substages:

  • Substage A – patient feels well
  • Substage B – patient is ill

How is lymphoma treated?

Lymphoma is often treated with chemotherapy drugs. Lymphosarcoma are among the most chemotherapy-responsive tumors seen in veterinary medicine, and most dogs tolerate chemotherapy well with minimal impact on their quality of life.

The best responses in terms of length of tumor control and survival are generally seen with the administration of more than one chemotherapy drug, although there are approaches that involve administration of a single drug. Chemotherapy drugs commonly used include doxorubicin, vincristine, cyclophosphamide, prednisone, and L-Aspariginase. In some dogs with localized disease, surgery or radiation therapy can also play a role in treatment.

What is the prognosis for a dog with lymphoma?

The prognosis for dogs with lymphoma is highly variable and depends on the clinical stage. Dogs in lower stages of the disease and that feel well will do better with treatment than dogs that are ill and have more advanced disease.

Lymphoma is not generally viewed as curable in dogs, although some will experience what seems to be a cure with appropriate treatment. A dog can start with one stage of the disease and progress over time to another (usually more advanced) stage.

Most dogs treated with chemotherapy will experience a remission, a period in which there is no detectable cancer, and the dog feels well. Remission times are variable, but most dogs with the lymph node forms of lymphoma will have initial remissions lasting in the range of 6-9 months before evidence of the tumor is seen again; second remissions can be achieved in many of these dogs, but any subsequent remission is expected to be shorter in duration than the first.

Survival times for most dogs treated with combination chemotherapy protocols are in the range of approximately 1 year.

Where can I get help if my dog has lymphoma?

Cancer of any kind is a diagnosis no pet owner wants to hear, but our board-certified veterinary oncologists can help you get an accurate diagnosis and develop a treatment plan. Call 509-335-0711 to schedule an appointment or visit our oncology webpage for more information.

This information is not meant to be a substitute for veterinary care. Always follow the instructions provided by your veterinarian. Washington State University assumes no liability for injury to you or your pet incurred by following these descriptions or procedures.