Swollen Lymph Nodes in Cats: When It’s Not Cancer (And When It Might Be)

What are lymph nodes and what do they do for your cat’s body

Your cat has lymph nodes all over their body; some locations that you can encounter would include under the jaw, in front of the shoulders, in your cat’s armpits, in the groin area, and behind the knees. There are many lymph nodes inside the body as well.

Lymph nodes are a main player in the lymphatic system, which is an integral part of the immune system. The lymphatic system helps the body fight infections and maintain fluid levels in the body. 

You can learn more in detail about how the lymphatic system works in cats in our post here.

Lymph nodes act as checkpoints throughout the lymphatic system which filter blood and fluid. They work to pull harmful substances or cells out of the body and prevent them from spreading further and creating a larger health problem. 

Because lymph nodes are so important for keeping threats out of the bloodstream and body overall, sometimes whatever has been pulled out of the lymph fluid passing through can lead to a negative reaction from the lymph node, leading to a noticeable swelling. 

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What Causes Swollen Lymph Nodes in Cats that Aren’t Cancer?

While it is very easy to jump to the conclusion that any swelling or lump or bump on your pet’s body is cancer, there are many additional reasons that a part of the immune system may have a reaction like swelling. 

Because lymph nodes function as a filtration station for the immune system, they are often exposed to infectious agents before the rest of the body, and so the reaction of the lymph nodes is a direct response to their effort in protecting the body from potential threats. 

Infections 

Bacterial infections are more likely to develop abscesses within the lymph nodes, which an lead to swelling. Fungal and viral infections may also cause swollen lymph nodes in cats, though they are less commonly the cause than bacterial infections are. 

Signs your cat may have an infection leading to their swollen lymph nodes include fever, lack of appetite, runny nose or eyes, vomiting and signs of pain, lethargy, and even possibly depression.^1,2,3,4,5 

Allergic reactions or Vaccine responses

Allergies can also cause lymph nodes on your cat to swell. Food, pollen or other environmental factors can trigger your cat’s lymph nodes to create inflammation that can be noticeable to a pet parent. 

In a similar way, vaccines can trigger an inflammatory response by your cat’s lymph nodes. Vaccines are designed to expose your cat to a small amount of a virus or bacteria to teach your cat’s immune system how to fight it off if it were to be exposed fully to the illness. Because of the inherent way that vaccines are designed it can be stressful for your cat’s immune system and can lead to their lymph nodes swelling.^2,5 

Tick-borne Diseases

There are several tick-borne diseases that can affect your cat and lead them to having swollen lymph nodes. Swelling in the lymph nodes is one of the more common symptoms of tick-borne diseases, along with fever, lethargy, joint pain or trouble walking, and weakness leading to diminished movement.² 
It’s always important to protect your cat from these diseases, especially if you allow your cat outside. Indoor cats, of course, are still at risk for tick-borne diseases—though at a significantly smaller risk than their outdoor-friendly counterparts. There are many ways to approach tick prevention for your cat, ask your vet for recommendations for tick prevention.⁷ 

If you ever do find a tick on your feline friend, you should remain calm and safely remove the tick from their body. If possible, keep the tick in a container to show your vet when you are able to get your cat checked out. Most ticks don’t carry diseases, but those that do make a big impact, and it’s always better to play it safe and make sure your cat is taken care of by getting checked out at the vet before assuming all is good or bad.⁶ 

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Signs a Swollen Lymph Node May Be Cancer 

Some common symptoms that lymph node swelling may be caused by cancer—but are not exclusive to cancer—include vomiting, weight loss, diarrhea, lethargy, appetite changes, excessive drinking and urinating, and nausea. Often lymph node swelling is not painful when it is cancer related.

The most common form of cancer that is signified by a swollen lymph node is lymphoma, a cancer of lymphocyte cells. The most frequently diagnosed type of lymphoma in cats is gastrointestinal, also called alimentary lymphoma. Most of the symptoms that cats with alimentary lymphoma experience are related to the gastrointestinal tract, but there are a few other variations of lymphoma that cats can be diagnosed with that are less common than alimentary. One of the other forms is multicentric which has an earlier appearance of swollen lymph nodes as a symptom of the cancer’s presence.⁸ 

While lymphoma is a cancer that is expressed mainly in lymph nodes throughout the body, there are other cancers that can spread to the lymph nodes as a secondary cancer location. Mast Cell tumors that are intestinal can spread to local lymph nodes and can cause partial obstruction of the intestines if the tumor gets large enough. 

It would be great if we pet parents had the ability to look at a bump on our animals and find the defining features that say whether it is cancerous or not, but with lymph nodes it’s simply not possible to see the cause of the swelling with the naked eye, and requires vet intervention to make a diagnosis and identify what your next steps should be for your cat’s treatment—if any is necessary. 

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How a Cat’s Swollen Lymph Node is Diagnosed 

The way that a swelling or a bump on your cat is diagnosed will generally start the same way.  

Once you notice a swollen lymph node and take your cat to the veterinarian, the vet will start by performing a general physical examination to assess your pet’s overall wellbeing, as well as check out the physical aspects of the bump and your cat’s reactions to being examined. 

After the initial assessment of your cat’s overall health, your vet will collect a sample of cells from the swollen lymph node to look at under a microscope. The process of getting these cells is called an FNA or Fine Needle Aspirate, where a small, narrow needle is inserted into the area of concern and a sample of cells is pulled into a waiting empty syringe. The cell sample is then looked at under the microscope in order for your vet to evaluate whether it qualifies for lab testing (cytology), or if the vet is able to identify the issue right there in the clinic itself.⁸ 

There may be additional testing required on a case-by-case basis that can include blood work, imaging, and urinalysis to get a fuller picture of the individual patient’s needs. 

Treatment for swollen lymph nodes can require many different approaches depending on the cause, so it’s important to meet with your vet and never make any assumptions about the cause or the best method to treat swollen lymph nodes on your cats without expert guidance. 

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ImpriMed is Helping Vets Diagnose Feline Lymphoma with Accuracy

If your cat has been affected by feline lymphoma or feline leukemia, ImpriMed can help your vet find the most accurate diagnosis, and add to an ever growing database of information on feline lymphoma and leukemia to help develop treatments in the future. 

You can learn more about how ImpriMed helps with diagnosing your cat’s swollen lymph node here.

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