Swollen lymph nodes in cats are never normal, and the treatment depends entirely on what’s causing the swelling. The underlying cause could be anything from a localized bacterial infection that clears with antibiotics to lymphoma, the most common cancer in cats. Because the range of possibilities is so wide, a veterinary exam and diagnostic testing are the essential first steps before any treatment can begin.
Why Lymph Nodes Swell
Lymph nodes are small, bean-shaped filters scattered throughout your cat’s body. They trap bacteria, viruses, and abnormal cells, then activate immune responses against them. When a lymph node is working overtime to fight something off, it fills with white blood cells and swells. This swelling, called lymphadenopathy, is a symptom rather than a disease on its own.
The four broad categories of causes are bacterial infections, viral infections (particularly feline leukemia virus and feline immunodeficiency virus), fungal infections, and cancer. Reactive swelling from a nearby wound or abscess is probably the most common reason a cat owner notices a lump, but lymphoma accounts for a significant share of cases, especially in older cats. Pinpointing which category your cat falls into determines the entire treatment path.
Where to Check for Swollen Nodes
Cats have five pairs of lymph nodes close enough to the surface that you can feel them during a gentle exam at home. Knowing their locations helps you spot changes early and describe them accurately to your vet.
- Mandibular: At the angle of the jawbone on each side, tucked just beneath the skin near where the jaw meets the neck.
- Superficial cervical: In front of the shoulder blades, along the sides and base of the neck.
- Axillary: In the “armpit” area on the inner surface of each front leg where it meets the chest.
- Inguinal: In the groin area on the inner thigh, near the lower belly.
- Popliteal: Behind the knee joint on each back leg, nestled between the muscles at the top of the calf.
Healthy lymph nodes in cats are small (often pea-sized or smaller) and can be difficult to feel at all. If a node feels obviously enlarged, firm, or your cat flinches when you touch it, that’s worth a vet visit. Swelling in multiple locations at once is more concerning than a single enlarged node near a visible wound.
How Vets Identify the Cause
Your vet will typically start with blood work to check for infection, inflammation, and viral diseases like feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV). The next step is usually a fine needle aspirate, where a small needle is inserted into the swollen node to collect cells for examination under a microscope. This is quick, minimally painful, and often doesn’t require sedation. Lab fees for a fine needle aspirate run roughly $48 to $70, depending on how many nodes are sampled.
If the aspirate doesn’t give a clear answer, a surgical biopsy removes a larger tissue sample. This costs more (around $89 for the lab analysis alone, plus the cost of the procedure itself) but provides a definitive diagnosis in most cases. For suspected lymphoma, the biopsy also helps classify the cancer as small cell or large cell, which has a major impact on prognosis and treatment.
Treating Bacterial Infections
When a bacterial infection is behind the swelling, antibiotics are the primary treatment. This is the most straightforward scenario. A cat with an abscess from a bite wound, for example, will typically receive a course of antibiotics lasting 10 to 14 days. The swollen node should shrink as the underlying infection clears.
If your cat has a localized abscess causing the node to swell, your vet may also need to drain the abscess and flush the wound. You’ll likely be asked to monitor the node size at home during and after the antibiotic course. If the node hasn’t returned to normal by the time antibiotics are finished, your vet may want to run additional diagnostics to rule out something more serious.
Managing Viral Infections
FeLV and FIV both suppress the immune system and can cause generalized lymph node swelling, sometimes as one of the earliest signs of infection. Unfortunately, there is no cure for either virus. Treatment focuses on managing the specific problems that arise rather than eliminating the virus itself.
For an FeLV- or FIV-positive cat with swollen nodes, the vet will look for secondary infections that the weakened immune system has allowed to take hold. Common bacteria, viruses, and fungi that wouldn’t normally cause illness in a healthy cat can trigger severe disease in immunocompromised cats. These secondary infections are treated individually, with antibiotics for bacterial infections, antifungals for fungal problems, and so on. Careful ongoing monitoring of weight, appetite, activity level, and the appearance of the mouth and eyes is a core part of managing life with these viruses.
Treating Fungal Infections
Systemic fungal infections are less common but require long treatment courses. Cats in certain geographic regions can pick up infections like histoplasmosis, blastomycosis, or cryptococcosis, all of which can cause lymph node swelling as the fungus spreads through the body.
Antifungal medications are given orally, often daily, for extended periods. Treatment for histoplasmosis in cats typically lasts 9 to 12 months. Blastomycosis requires 60 to 90 days of treatment. Cryptococcosis can require 6 to 18 months. These long timelines can feel daunting, but fungal infections generally respond well to consistent medication. Your vet will monitor your cat’s bloodwork periodically during treatment, since some antifungal drugs can stress the liver.
Treatment for Lymphoma
Lymphoma is the most serious cause of swollen lymph nodes in cats, and it’s also the most common feline cancer overall. Treatment and prognosis depend heavily on the type.
Large Cell Lymphoma
This aggressive form is typically treated with a multi-drug chemotherapy protocol that combines several medications given in cycles, some by injection at the vet clinic and one (a steroid) taken at home. Between 50% and 75% of cats with gastrointestinal large cell lymphoma respond to this treatment, with a typical survival time of 6 to 9 months. Cats that achieve complete remission live longer, and a small percentage survive more than two years. An alternative oral chemotherapy option exists for cats that aren’t good candidates for the standard protocol, with a median survival of about 8 months in responders.
Cats generally tolerate chemotherapy better than humans do. Side effects like nausea and decreased appetite can occur but tend to be milder. Most cats maintain a reasonable quality of life during treatment, and your oncologist will adjust doses if side effects become significant.
Small Cell Lymphoma
This slower-growing form has a much better prognosis. Treatment involves oral medications given at home, typically a combination of a mild chemotherapy pill and a steroid. The trade-off is that treatment is ongoing and essentially chronic. With consistent medication, cats with small cell lymphoma often survive 2 to 3 years or more.
Nasal Lymphoma
Lymphoma confined to the nasal passages is treated with radiation, chemotherapy, or both, and carries an approximate prognosis of one year.
What You Can Do at Home
While treatment for the underlying cause is always a veterinary matter, there are practical things you can do at home to support your cat and catch problems early.
Get in the habit of running your hands along the five lymph node locations during petting sessions. Familiarize yourself with what feels normal so you can detect changes quickly. If your cat is being treated for an infection, track whether the swelling is decreasing over the expected timeline. Weight loss, poor appetite, lethargy, difficulty breathing, nasal discharge, or behavioral changes alongside swollen nodes all warrant a prompt vet visit, as these can signal that the condition is progressing or that a more serious cause is at play.
Keep your cat’s environment clean and low-stress during treatment. For cats on long courses of medication, setting phone reminders for doses helps maintain consistency, which is especially important for antifungal and chemotherapy protocols where gaps in treatment can reduce effectiveness. If your cat is FeLV- or FIV-positive, keeping them indoors protects both your cat from additional infections and other neighborhood cats from exposure.