Swollen Lymph Nodes in Cats — Symptom Decision Guide

A practical guide to recognizing and responding to swollen lymph nodes in cats. Learn likely causes, a decision tree for next steps, at-home checks, red flags, and why cytology matters.

Quick Assessment

Is this an emergency?

- YES — if your cat has rapid swelling, breathing difficulty, collapse, a very high fever (>104°F / 40°C), severe pain, or a draining wound with heavy bleeding. Seek emergency veterinary care.

- NO (but see vet same day/within 48 hours) — if swelling is new and the node is firm, growing, associated with weight loss, persistent fever (≥103°F / 39.4°C), or lasts >2 weeks.

Most common cause: reactive lymphadenopathy from local infection (bites, tooth disease, upper respiratory infection).

When to see a vet: any node that is larger than normal (>~1 cm), firm or fixed, progressively enlarging, or accompanied by systemic signs (fever, weight loss, decreased appetite).

What swollen lymph nodes look and feel like

Lymph nodes (lymphadenopathy) in cats can appear as small bumps under the skin. Common peripheral nodes you can feel are:

• Submandibular (under the jaw)
• Prescapular (in front of the shoulders)
• Axillary (armpit area)
• Inguinal (groin)
• Popliteal (behind the knee)

• Size: normal nodes in most cats are small and sometimes barely felt; nodes >1 cm or obviously larger than usual are suspicious.
• Consistency: soft and squishy often suggests inflammation; firm or hard suggests neoplasia or chronic disease.
• Mobility: freely movable nodes are less worrisome than fixed, immobile nodes.
• Pain: painful nodes often indicate infection or inflammation; painless enlargement can suggest neoplasia.
• Other signs: fever, loss of appetite, weight loss, oral disease, skin wounds, draining tracts.

Possible causes — ranked by likelihood (common → rare)

Decision tree — If [symptom] + [other sign] → likely [cause] → [action]

• If swollen node + recent bite/wound or abscess nearby → likely reactive infection/abscess → clean wound, monitor, see vet within 24–48 hours for drain/FNA/antibiotics.

• If swollen node(s) + painful, warm, red skin + fever (≥103°F / 39.4°C) → likely bacterial infection → urgent vet visit (same day) for exam, possible abscess drainage and antibiotics.

• If swollen node(s) + dental disease or sneezing/nasal discharge → likely reactive to oral/respiratory infection → schedule vet visit within a few days; dental exam and FNA may be recommended.

• If firm, painless, progressively enlarging nodes + weight loss or decreased appetite → likely lymphoma (or other neoplasia) → see vet promptly for FNA cytology ± biopsy, bloodwork, imaging (same week).

• If multiple regional nodes slowly enlarging over weeks/months with draining tracts → consider mycobacterial infection → see vet for culture/PCR, FNA/biopsy, and specialized therapy (often long-term antibiotics).

• If generalized lymphadenopathy + young cat or known exposure to other FeLV-positive cats → consider FeLV-associated disease → test for FeLV (ELISA) and perform cytology/biopsy.

Home assessment steps (what to check and how)

Keep a note of your findings to share with your vet.

When it's an emergency — red flags (seek immediate care)

• Rapidly enlarging nodes over hours to days
• Severe pain, vocalization, collapse, weakness
• Difficulty breathing, open-mouth breathing, severe respiratory distress
• High fever ≥104°F (40°C)
• Heavy bleeding or large open wounds/draining tracts with systemic signs
• Severe dehydration or seizures

When to schedule a regular vet visit (non-urgent but needed)

• Node(s) clearly enlarged for >48 hours without improvement
• Node >1 cm, firm, or fixed in place
• Persistent or recurrent swelling for >2 weeks
• Additional signs: weight loss, decreased appetite, intermittent fever (≥103°F / 39.4°C), persistent lethargy
• Known exposure to FeLV/FIV-positive cats or new outdoor exposure that increases infection risk

Home care (safe supportive measures while you arrange care)

• Keep the cat comfortable and hydrated. Offer palatable, warm food and fresh water.
• Maintain a quiet, warm resting area and minimize stress.
• Do NOT lance, squeeze, or try to “pop” nodes or draining tracts at home.
• Don’t give antibiotics, corticosteroids, or injectable medications without veterinary guidance — they can mask signs and complicate diagnosis.
• For painful, swollen areas due to external abscesses, a warm compress applied gently for 5–10 minutes a few times daily can ease discomfort while you seek veterinary care.
• If the cat is on immunosuppressive drugs or has other medical conditions, contact your vet promptly for tailored advice.

Why cytology (FNA) is important

Fine-needle aspiration (FNA) cytology is a minimally invasive test where a small needle collects cells from the enlarged node for microscopic evaluation. Why it matters:

• Distinguishes inflammatory/reactive cells from cancerous lymphoid cells in many cases
• Can often identify infectious organisms (bacteria, fungi, some parasites) or suggest mycobacterial infection
• Quick, low-risk, and often performed awake with gentle restraint

• Cytology can be inconclusive; it may not definitively subtype lymphoma or differentiate certain chronic inflammation from early neoplasia.
• If cytology is unclear, the vet may recommend a biopsy for histopathology, immunophenotyping (B vs T cell), flow cytometry, or PCR for antigen receptor rearrangement (PARR) to assess clonality.

What your vet will likely do

• Physical exam and full history
• Bloodwork (CBC, chemistry) to look for infection, anemia, organ function
• FeLV/FIV testing
• FNA cytology of the node(s) ± bacterial culture, or referral for biopsy
• Thoracic/abdominal imaging (X-rays, ultrasound) if systemic disease suspected
• Additional specialized testing (PARR, immunophenotyping) if lymphoma is suspected

What to tell your vet — essential information

Bring a concise history including:

• When you first noticed swelling and how it has changed
• Which node locations are affected and whether swelling is single or multiple
• Any wounds, fights, scratches, or dental problems
• Appetite, weight change, vomiting, diarrhea, coughing, sneezing, or lethargy
• Current medications, vaccines, and FeLV/FIV status
• Indoor/outdoor status and known exposures to other animals or wildlife
• Any prior similar episodes and previous diagnostic results

Takeaway

Swollen lymph nodes in cats are a common sign with many causes. Most often they reflect a localized infection or inflammation, but they can also be an important clue to serious conditions such as lymphoma, FeLV-associated disease, or mycobacterial infection. Timely vet assessment — including FNA cytology — is often the key to distinguishing these causes and guiding appropriate treatment. In urgent situations (rapid enlargement, severe systemic signs, difficulty breathing), seek emergency care immediately.

Sources and further reading

• Merck Veterinary Manual — Lymphadenopathy in Small Animals. https://www.merckvetmanual.com/generalized-conditions/lymphadenopathy/overview-of-lymphadenopathy
• Merck Veterinary Manual — Feline Lymphoma. https://www.merckvetmanual.com/cat-owners/cats-and-cancer/lymphoma-in-cats

Frequently Asked Questions