Lymphoma in Dogs

Medically Reviewed by Amy Flowers, DVM on February 20, 2024
6 min read

Canine lymphoma is the name for a common group of cancers in dogs. It's similar to a type of cancer that people get called non-Hodgkin's lymphoma.

Lymphomas are one of the most common types of cancer found in dogs. They account for 7%-14% of all canine cancers. More than 30 types have been identified. Their symptoms and the way they progress vary.

Some lymphomas can't be treated, while others are chronic and develop slowly. Chronic lymphomas can be managed with treatment. Although your dog can get lymphoma in any part of its body, they usually start in the lymph nodes. These are small glands that are part of your dog's immune system. From there, they spread to other organs, including the bone marrow, liver, and spleen.

Canine lymphoma usually can't be cured. But chemotherapy could buy you and your pet more quality time together.

Lymphoma refers to cancer starting in the lymphocytes. These are white blood cells that play a key role in the body's immune response. The spleen, lymph nodes, and bone marrow have large amounts of lymphocytes.

Similar drugs are used to treat both lymphoma in dogs and non-Hodgkin's lymphoma in humans.

Experts aren't sure why dogs get lymphoma. Researchers think genetics and conditions outside and inside our homes play a role.

Dogs are in the same environment as humans, so they're exposed to many things that may cause cancer, such as weed killer. Scientists also have looked into other possible causes, including viruses and bacteria.

Dogs can get over 30 types of lymphoma. They vary in how fast they spread, the symptoms they can bring on, and how long dogs tend to live with them.

Your vet might diagnose your dog with one of these four:

  1. Multicentric lymphoma. This is the most common kind of canine lymphoma. Up to 85% of cases are this type, which first affects the lymph nodes.
  2. Alimentary lymphoma (also called gastrointestinal lymphoma). This is the second most common type, and it makes up less than 10% of cases of lymphoma in dogs.
  3. Mediastinal lymphoma. This rare type enlarges certain parts of the lymph system (tissues and organs that make, store, and carry white blood cells) in or around the chest. It can cause a lump or fluid buildup that makes it harder for your dog to breathe.
  4. Extranodal lymphoma (including cutaneous lymphoma). This type affects a specific organ or set of organs, like the skin, eyes, kidneys, lungs, or central nervous system. Most of the time, it affects the skin (called cutaneous lymphoma). It may also affect the gums, lips, and roof of the mouth.

The most common sign you might notice is one or more firm, enlarged lymph nodes on your pet's body. When they're enlarged, they feel like hard, rubbery lumps under the skin. They're not painful. They could show up in places like:

  • Under the neck or jaw
  • Behind the knees
  • In front of the shoulders
  • In the armpits

If you notice lumps like these on your dog, ask your vet to check them, even if your pet seems fine otherwise.

Lymphoma can also bring on symptoms like:

  • Reduced appetite
  • Feeling tired
  • Weight loss
  • Swelling in the face or legs
  • Increased thirst
  • More frequent peeing
  • Diarrhea
  • Throwing up
  • Trouble breathing

Dogs with cutaneous lymphoma have red, itchy, dry, and flaky patches of skin. As the disease gets worse, the skin becomes thick and moist with open sores. You may notice lumps in your dog's skin.

Other skin conditions can cause similar symptoms. Your vet may first treat the symptoms as an allergy or infection. If your dog doesn't improve, a skin biopsy is the next step That's the only way to diagnose cutaneous lymphoma.

Symptoms of gastrointestinal lymphoma are:

  • Weight loss
  • Watery diarrhea
  • Throwing up

If your dog has lymphoma, they may not seem sick. Or they may have only mild symptoms, like feeling tired and not wanting to eat. Your dog's symptoms and how serious they are will depend on:

  • How advanced the cancer is
  • Which organs are affected
  • The type of lymphoma

To find out if your dog has lymphoma, your vet may do a biopsy. The process may start with a fine needle aspiration, which uses a thin needle to remove a sample from your dog's lymph nodes or organs.

Another type of biopsy involves a minor surgery. The vet will cut out a larger piece of a lymph node or other organ that might have cancer in it. Whether your dog has a needle aspiration or larger biopsy, the sample will tested for cancer.

If the results show your dog has lymphoma, your vet may suggest that your pet get staging tests. These show how far the cancer has spread. In general, the more body parts it involves, the more serious your dog's condition may be.

Staging tests include blood tests, pee tests, X-rays, ultrasounds, and more.

The five stages of canine lymphoma reflect the extent of cancer in your dog's body:

  • Stage I: A single lymph node is enlarged.
  • Stage II: More than one node is enlarged on either the front half or back half of your dog's body.
  • Stage III: More than one node is enlarged on both the front and back of your dog's body.
  • Stage IV: The lymphoma has reached the liver, spleen, or both.
  • Stage V: The lymphoma affects the bone marrow or other organs (like the gut, skin, or nervous system).

Each stage can also be divided further. Your vet may use the term "substage A" to mean your dog feels well, and the term "substage B" to mean they feel sick.

Learning that your dog has cancer can be heartbreaking. But treatment could extend their life.

The most effective treatment of lymphoma in dogs is chemotherapy. There are many chemo drugs. The ones your vet suggests for your pet will depend on the type of lymphoma they have.

Some chemo drugs are given to dogs through an IV line, and some are given by mouth. Dogs often get a combination of these meds.

Your dog may need weekly chemo treatments for several months.

One treatment for dogs with multicentric lymphoma is based on something called the CHOP protocol used to treat lymphomas in humans.

If your dog doesn't respond to chemotherapy, that particular chemo drug might not work on the cancer. That's called drug resistance. Over time, most lymphomas become drug-resistant. Your vet can try treatments to reverse drug resistance.

Dogs don't usually get very sick from chemo or lose their hair the way some humans do. Certain breeds do lose hair, though, including sheepdogs, poodles, and Bichon Frise.

Some common side effects are:

  • Not wanting to eat
  • Being less active
  • Vomiting or diarrhea that lasts 1 or 2 days

Always call your dog's vet or cancer doctor if they have severe side effects. They may be able to prescribe medicines that will help.

Along with chemo, vets sometimes advise treatments like radiation therapy or surgery.

Ask your vet to walk you through your dog's treatment options. Have them explain the pros and cons of each. Together, you can decide which treatment (if any) is right for your dog.

Your dog's life expectancy depends on many things, like the stage of the cancer and which treatment you choose.

Most dogs who get chemotherapy for lymphoma go into remission. "Partial remission" means that some, but not all, of your dog's signs of cancer have gone away. "Total remission" means all symptoms of the disease have disappeared, although cancer could still be in their body.

Neither type of remission is a cure. But often, dogs who get lymphoma treatment go into total remission for many months.

Lymphoma in dogs usually comes back, though. Your vet may call this a "relapse." Treatment helps some dogs get back into remission. But when the cancer returns, it may be harder to treat. Over time, lymphoma cells become resistant to chemotherapy.

Keep in touch with your vet while your dog gets lymphoma treatment or recovers from it. You'll learn what to expect if the disease gets worse and how to keep your pet as happy and comfortable as possible. You can also ask the vet about hospice care and euthanasia (putting your dog to sleep) if the lymphoma can no longer be treated.