Cat Lump on Paw: Pododermatitis and Other Causes
By Dr. Zubair Khalid, DVM, MS, PhD ·
A cat lump on paw is most often swelling or a mass on the paw pad or between the toes. Common causes include pododermatitis (inflammation of the paw pads), infections, foreign material like cat litter silica, and skin tumors. Some lumps are painful, some are not, and a few need a biopsy to identify.
This article is educational and is not a substitute for veterinary diagnosis or treatment.
Quick Answer
- A lump or swelling on a cat's paw can come from inflammation (pododermatitis), infection, a foreign body reaction, or a tumor [1][2].
- Plasma cell pododermatitis is an uncommon paw pad disease that causes soft, diffuse swelling, often on multiple pads [3].
- Paw pad swelling, ulceration, and bleeding can be linked to silica (clay cat litter) granulomas in some cats [4].
- Skin tumors in cats, including basal cell carcinomas and mast cell tumors, can appear as lumps or ulcers on the legs and paws [2].
- Any paw lump that grows, bleeds, or causes limping needs a veterinary exam, and a biopsy is often the only way to know the cause.
What Is a Cat Lump on Paw?
A lump on a cat's paw is any new bump, swelling, or thickened area on the paw pad, between the toes, or on the skin of the foot. The medical word for inflammation of the paw is pododermatitis. Dermatitis is a general term for skin inflammation, and it is used until a specific diagnosis is reached [1].
Pododermatitis in cats can affect one pad or several. It can be soft and squishy, firm, ulcerated, or crusted. Some cats have swelling that feels like a spongy cushion. Others have a distinct raised mass.
Plasma cell pododermatitis is one specific type. In this condition, the cat's own immune cells (plasma cells) build up in the paw pads. A recent case report describes soft, diffuse swelling across multiple paw pads, with severe swelling of the nasal bridge in one cat [3]. The same report suggests this condition may be a hypersensitivity reaction pattern, meaning it could be an allergic-type response instead of a single distinct disease [3].
Other lumps are caused by infections, foreign material, or tumors. Because the causes are so different, the treatment depends entirely on what is actually growing or swelling in the paw.
Signs Owners Notice
You may see one or more of these signs:
- A visible bump or swollen pad on one or more paws
- Soft, squishy, or firm swelling of the paw pad
- Redness, purple or violet discoloration of the pad [5]
- Peeling, crusting, or ulceration of the pad surface [5]
- Bleeding from the pad or a draining tract [4]
- Limping or reluctance to walk on the paw
- Licking or chewing at the foot
- Hair loss around the lump
- Foul odor if infection is present
Some cats with plasma cell pododermatitis have swelling on multiple metacarpal, metatarsal, and digital paw pads [5]. In one reported case, a 2-year-old male cat had alopecia, skin peeling, and red swelling in the left metacarpal paw pad, along with softening, ulceration, and crusts on several pads [5].
If your cat is limping, see our guide to Cat Limping Paw for help deciding how urgent the problem is.
Causes and Risk Factors
Plasma Cell Pododermatitis
Plasma cell pododermatitis is uncommon. A case series of 25 cats found that affected cats were most commonly young (under 5 years old) and castrated males [6]. The same series found marked anemia, high globulin levels, and protein in the urine in these cats, and it suggested that cats with this condition may be predisposed to glomerular (kidney filter) disease [6].
One case was linked to feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV) infection [5]. The cat was positive for both viruses on blood testing, and paw pad biopsies showed FeLV in the tissue [5]. This does not mean every cat with pododermatitis has these viruses, but it is one reason your vet may recommend virus testing.
Infections
Bacterial, fungal, and parasitic infections can all cause paw lumps [1]. A granulomatous pododermatitis caused by the fungus Fusarium proliferatum was reported in a 10-year-old female cat with a mass on the foot pad of the right hind leg [7]. Another report identified a novel fungus, Paraconiothyrium cyclothyrioides, causing pus-filled fungal pododermatitis in a cat and a dog [8].
Foreign Material (Cat Litter) Granulomas
Silica is common in clay-based cat litter. A study of 13 paw biopsies from cats found granulomatous inflammation containing silica-like material, and the material matched several brands of silica-based cat litter on Raman spectroscopy [4]. Ten of the 13 biopsies also showed evidence of plasma cell pododermatitis, which suggests the two conditions may overlap [4]. Front paws were often affected, with chronic or intermittent swelling, ulceration, bleeding, or draining tracts [4].
Tumors
Skin tumors can grow on the legs and paws. Basal cell carcinomas are malignant tumors seen most often in older cats, and Persians may be more prone to them [2]. They often look like ulcers on the head, legs, or neck and are not usually raised above the skin [2]. Mast cell tumors are the second most common skin tumor in cats, and more than one tumor may be present [2]. A form of skin lymphosarcoma can appear as thick patches or lumps with hair loss or ulcers, and it spreads quickly [2].
Other Causes
Allergic skin disease, trauma, burns, and irritant contact can all inflame the paw [1]. If the lump is itchy and scaly, see Cat Skin Rash on Paws: Causes and Home Care.
How Veterinarians Diagnose a Paw Lump
Your veterinarian starts with a full history and physical exam. They will look at all four paws, not only the one you noticed. They will check for symmetry, discharge, odor, and pain.
Common First Tests
- Skin scrapes and cytology (cell samples) to look for infection or inflammatory cells
- Fungal culture or PCR testing if a fungal cause is suspected
- Blood work, including a complete blood count and serum biochemistry
- Virus testing for FeLV and FIV
- Urinalysis, especially if kidney disease is a concern [6]
- Imaging such as X-rays if a deeper mass or bone involvement is possible
Biopsy
A biopsy is often the only way to tell pododermatitis from a tumor or a foreign body reaction. In the silica study, all 13 diagnoses came from surgical biopsies of the paws or paw pads [4]. In the plasma cell pododermatitis case, the diagnosis was confirmed with histopathology and immunohistochemistry on paw pad biopsies [5].
During a biopsy, your vet removes a small piece of tissue and sends it to a lab. The lab looks at the cells under a microscope. This can show plasma cells, fungal hyphae, silica particles, or tumor cells [7][5][4].
If your cat has a lump elsewhere on the body too, read Cat Skin Bumps and Lumps: When to See a Vet and When to Monitor.
Treatment Options
Treatment depends on the diagnosis. There is no single treatment for every paw lump.
| Cause | Typical Treatment Approach |
|---|---|
| Plasma cell pododermatitis | Immune-suppressing medication, treatment of any underlying virus or kidney disease [5][6] |
| Bacterial infection | Antibiotics chosen by your vet |
| Fungal infection | Antifungal medication, sometimes surgery [7][8] |
| Silica or foreign body granuloma | Removal of the material, management of chronic inflammation [4] |
| Benign tumor | Surgical removal |
| Malignant tumor | Surgical removal, possible referral to a veterinary oncologist [2] |
For plasma cell pododermatitis, your vet may prescribe medications that calm the immune system. The exact drug and dose are calculated from your cat's weight and health, so no dose is given here. If your cat tests positive for FeLV or FIV, that changes the treatment plan and the outlook [5].
For tumors, surgical removal is the treatment of choice for basal cell carcinomas [2]. These tumors spread to nearby skin but seldom spread to other organs [2]. Skin lymphosarcoma spreads quickly, and a definitive treatment is unknown, though several therapies may be available through your veterinarian or a veterinary oncologist [2].
If a fungal infection is the cause, treatment can take months. Some fungal paw infections are rare and may need specialized testing to identify the exact organism [7][8].
Recovery, Outlook, and Long-Term Management
Recovery varies widely. A cat with a simple bacterial infection may improve within days of starting antibiotics. A cat with a fungal infection may need months of treatment. A cat with plasma cell pododermatitis may need long-term medication and monitoring.
The case series of 25 cats with plasma cell pododermatitis and kidney disease collected survival times and treatment protocols, which shows that these cats need ongoing care, not a one-time visit [6]. Because kidney disease was common in that group, your vet may want to recheck urine and blood values over time [6].
Cats with silica granulomas often have chronic or intermittent swelling and draining tracts, which means the problem can come back or persist [4]. If your cat's litter is clay-based, your vet may discuss whether changing litter could help, though this has not been proven as a treatment.
For any cat with a malignant tumor, follow-up visits are needed to check for recurrence. Even when a solitary lymphosarcoma lump is removed, recurrence is likely [2].
Prevention
You cannot prevent every paw lump, but you can lower some risks.
- Check your cat's paws weekly. Look between the toes and at each pad.
- Keep the litter box clean and watch for pad irritation.
- Ask your vet about litter type if your cat has repeated pad problems, since silica in clay litter has been linked to granulomas [4].
- Keep your cat up to date on FeLV and FIV testing and prevention, since one pododermatitis case was linked to both viruses [5].
- Treat any paw wound early, before infection sets in.
- Schedule routine exams for older cats, since skin tumors are more common with age [2].
Limitations and When to Contact a Veterinarian
This article cannot tell you what your cat's lump is. Only a veterinarian can examine the tissue, run tests, and make a diagnosis for your individual cat.
Contact a veterinarian the same day if you see:
- A new lump that is growing quickly
- Bleeding or a draining tract from the paw [4]
- A pad that is ulcerated or has purple or violet discoloration [5]
- Limping that is getting worse
- Swelling on multiple paws [5][3]
Go to an emergency clinic now if:
- Your cat will not put weight on the leg at all
- There is heavy bleeding that will not stop
- The paw is swollen suddenly and your cat is in severe pain
- Your cat is lethargic, not eating, or vomiting along with the paw problem
Schedule a routine visit if:
- The lump is small, not growing, and your cat is walking normally
- You notice mild swelling that comes and goes
- You want a baseline check on an older cat
Frequently Asked Questions
Is a lump on my cat's paw always cancer?
No. Many paw lumps are caused by inflammation, infection, or foreign material reactions. Plasma cell pododermatitis, fungal infections, and silica granulomas are all non-cancerous causes [7][5][4]. However, tumors like basal cell carcinomas and mast cell tumors can also appear on the legs and paws, so a biopsy is often needed to tell the difference [2].
Can cat litter cause a lump on my cat's paw?
It may contribute in some cases. A study of 13 cat paw biopsies found silica particles inside inflamed tissue, and the silica matched several brands of clay-based cat litter [4]. Most of those biopsies also showed plasma cell pododermatitis, so the relationship is not fully clear [4]. If your cat has repeated paw problems, talk to your vet about litter options.
What does plasma cell pododermatitis look like?
It usually looks like soft, diffuse swelling of one or more paw pads. The pads may be red, purple, or violet, and the surface can peel, ulcerate, or form crusts [5][3]. Some cats also have swelling on the nasal bridge [3]. It is diagnosed with a biopsy, not by appearance alone [5].
Do paw lumps in cats hurt?
Not always. Some cats with plasma cell pododermatitis have only mild itching, while others have painful swelling [3]. Tumors may or may not be painful. Any lump that causes limping, licking, or reluctance to walk should be checked, because pain is a sign that the problem is affecting how your cat uses the paw.
Will my cat need surgery for a paw lump?
Sometimes. Surgery is the treatment of choice for basal cell carcinomas and other removable tumors [2]. Biopsies also involve a small surgical procedure to collect tissue [4]. Many inflammatory and infectious causes are treated with medication instead of surgery, so the answer depends on the diagnosis.
Related Articles
- Cat Skin Rash on Paws: Causes and Home Care
- Cat Skin Bumps and Lumps: When to See a Vet and When to Monitor
- Cat Limping Paw
- Can Cats Get Psoriasis
- Dog Skin Rash on Paws: Causes and Treatment
- Dog Paw Allergies: Signs, Causes, and Treatment
References
- Dermatitis and Dermatologic Problems in Cats - Cat Owners. Merck Veterinary Manual.
- Tumors of the Skin in Cats - Cat Owners. Merck Veterinary Manual.
- Feline plasma cell pododermatitis with nasal involvement suggesting a hypersensitivity associated reaction pattern - a case report and review of the literature. Tierarztliche Praxis. Ausgabe K, Kleintiere/Heimtiere, 2026.
- Cutaneous silica-associated (cat litter) granulomas in the paws of 13 domestic cats. Veterinary pathology, 2026.
- Plasma Cell Pododermatitis Associated With Feline Leukemia Virus (FeLV) and Concomitant Feline Immunodeficiency Virus (FIV) Infection in a Cat. Topics in companion animal medicine, 2020.
- Feline plasma cell pododermatitis with concurrent glomerular disease: a case series of 25 cats. Journal of feline medicine and surgery, 2026.
- Granulomatous pododermatitis in the digits caused by Fusarium proliferatum in a cat. The Journal of veterinary medical science, 2014.
- Paraconiothyrium cyclothyrioides, a novel cutaneous fungal pathogen in a dog and a cat. Veterinary dermatology, 2023.