Lymphoma is a common type of malignant cancer in dogs. Cancer occurs when cells multiply uncontrollably, leading to tumors. These tumors grow and spread, destroying the body's healthy tissues.
Specifically, lymphoma is a cancer of the lymphatic system. The lymphatic system is part of the immune system in dogs, humans, and other animals. It includes lymph nodes, lymphatic vessels, and specialized organs like the spleen. These structures transport and support lymphocytes (white blood cells); healthy white blood cells protect the body from infection.
Types of Lymphoma in Dogs
There are four main types of lymphoma in dogs. Your veterinarian will perform a physical exam, blood tests, and other diagnostics to determine whether your dog has lymphoma.
Multicentric lymphoma is considered the most common form of lymphoma in dogs. Around 80% of dogs with lymphoma will have the multicentric type (1). Affected dogs often have the classical signs of lymphoma, such as swelling of multiple lymph nodes.
Also called alimentary lymphoma, this subtype of lymphoma affects the digestive tract. The digestive system contains its own lymphatic tissue where cancer may form. The symptoms of alimentary lymphoma can be vague, making it harder to diagnose.
This rare form of lymphoma affects lymphatic tissue in the area around the heart (mediastinum).
Extranodal lymphoma in dogs affects other organs outside the lymphatic system. White blood cells leave circulation and travel around the body to fight infection. In rare cases, this function leads to lymphoma of the skin, eyes, kidney, lung, or nervous system. Advanced stages of multicentric lymphoma can also spread to these areas.
Symptoms of Lymphoma in Dogs
Common Signs of Canine Lymphoma
How do you know if your dog has lymphoma? Clinical signs of dog lymphoma can vary depending on the disease stage and other factors. However, potential signs include:
Multiple enlarged lymph nodes
Multiple swollen lymph nodes are often the first symptom of canine lymphoma. You may notice enlarged lymph nodes at home, or your veterinarian may find them during their physical exam. Affected lymph nodes are usually firm, non-painful, and get bigger over the course of weeks to months.
Where Are My Dog's Lymph Nodes?
The lymph nodes your veterinarian checks during a physical exam come in pairs, one on the left side of the body and one on the right. They're located in your dog's neck, armpits, groin, and behind the knees.
Clinical Signs in Rare Types of Canine Lymphoma
As mentioned before, around 80% of dogs with lymphoma will get the multinodal type. Dogs with multinodal lymphoma often develop telltale symptoms. However, less common types like cutaneous lymphoma and alimentary lymphoma can have vague, nonspecific clinical signs.
For example, dogs with alimentary lymphoma may have vomiting, diarrhea, and weight loss without any enlarged peripheral lymph nodes. Dogs with mediastinal lymphoma may cough or have breathing trouble.
Nonspecific symptoms make rare types of dog lymphoma more difficult to diagnose. Fortunately, these types of canine lymphoma are rare.
If you're concerned that your dog may have lymphoma, visit your veterinarian. Your vet will perform a physical exam and diagnostic tests to determine the cause of your pup's illness.
How Veterinarians Diagnose Lymphoma in Dogs
Not every dog with swollen lymph nodes will have lymphoma. Your veterinarian will rule out other causes of lymph node swelling before diagnosing cancer.
The most common test used to diagnose dog lymphoma is a fine needle aspiration (FNA). During this test, the veterinarian samples the lymph node with a small needle. Cells that collect in the needle can then be examined with a microscope.
Does lymphoma in dogs show up in blood work? Often, your vet will recommend a blood panel if they suspect lymphoma. This test provides valuable information about your dog's overall health.
Blood work also reports white blood cell count, size, and other key factors for lymphoma in dogs. However, one or more additional tests like fine needle aspirates are needed to confirm canine lymphoma.
Lymph Node Biopsy
If your dog's fine needle aspiration results are inconclusive, your veterinarian may recommend a biopsy. During a biopsy, a small amount of tissue is surgically removed. The sample is then sent to a veterinary laboratory for special testing. Biopsies are also used to stage lymphoma in dogs.
What Causes Lymphoma in Dogs?
Higher Risk in Older Dogs
Similar to people, the risk of cancer goes up as dogs get older. Lymphoma is most common in middle-aged and senior dogs, but dogs of any age can be affected. If possible, older pups should receive more frequent veterinary check-ups. That way, symptoms of lymphoma and other conditions can be caught early.
Dog Breeds Predisposed to Lymphoma
We don't fully understand the causes of lymphoma in dogs yet; dogs of any breed can develop this type of cancer. However, some dog breeds are more likely to develop lymphoma than others (2). This finding suggests that lymphoma may have a genetic component.
Dog breeds thought to be predisposed to lymphoma include:
Treatment of Canine Lymphoma
Chemotherapy is the main strategy used to treat lymphoma in dogs. There are multiple chemotherapy protocols available, but most involve weekly injections or infusions at a veterinary clinic. If you're worried about your dog's quality of life during treatment, discuss concerns with your vet.
Fortunately, dogs tolerate chemotherapy more easily than people. They often act normally during treatment and rarely lose any fur.
Dogs that do experience chemotherapy side effects may have vomiting, diarrhea, loss of appetite, or irritation at the injection site. Your vet can prescribe medications or alter the chemotherapy protocol if side effects arise.
Canine Lymphoma Prognosis
Like in humans, the treatment options and outlook for lymphoma in dogs depends on multiple factors. If your dog is diagnosed with lymphoma or lymphosarcoma, your veterinarian will recommend additional diagnostics, such as staging tests.
How long does a dog live with lymphoma? Without chemotherapy, dogs with lymphoma live an average of 4-6 weeks. Keep in mind that this range is only an average, and many dogs will have a shorter or longer life expectancy. Add-on treatments like steroids (prednisone) can make dogs with lymphoma more comfortable, but they don't reliably help survival time when used alone.
Is lymphoma curable in dogs? With chemotherapy, dog lymphoma can be put into remission. Remission is not the same as a cure. However, dogs in remission from lymphoma live symptom-free for an average of one year (1). Again, some dogs will have a longer than average life expectancy after treatment, others will have less time. Each case is unique.
Hospice Care for Dogs with Lymphoma
Unfortunately, there are situations where treating dog lymphoma is not feasible or likely to succeed. Eventually, most dogs will stop responding to chemotherapy after a period of remission. Your veterinarian will discuss likely treatment outcomes for your dog's lymphoma.
Ultimately, treating your dog's cancer is your decision, and declining treatment for your dog does not make you a bad person. Be honest with your veterinarian about how you're feeling, and ask questions about the options.
You can also talk to your veterinarian about hospice care, also known as palliative care or comfort care. The goal of hospice care is to give your dog as many happy, comfortable days as possible near the end of their life (3). Your vet can also give advice for knowing when it's time to say goodbye.
Canine Lymphoma: Conclusion
If you're concerned about lymphoma in dogs, the best thing you can do is take your pup in for regular veterinary check-ups. These visits raise the chance of catching lymphoma early, meaning that treatment is more likely to be effective.
If your dog has been diagnosed with lymphoma, continue working closely with your veterinarian. Your vet will tailor their lymphoma treatment plan to your dog's unique needs.