By Dial A Vet Veterinary Team
Finding a new lump on your dog or cat is unsettling, and the internet is full of photos that make every skin tag look like cancer or every cancer look harmless. The honest answer from vets is that you cannot reliably tell by looking. A soft, dangling skin tag is usually benign, but mast cell tumours in dogs are known as "the great pretender" because they can look like almost anything, including a tag or a wart. Australian sunshine adds another risk: white-eared cats and pale-skinned dogs develop sun-related skin cancers more often here than in many countries. This guide explains which features are reassuring, which are not, and the simple test that answers the question.
Key takeaways
- True skin tags are soft, small, and benign, but some cancers can look similar.
- A quick needle sample (fine needle aspirate) is the usual first test and often gives an answer the same day or within a few days.
- A common vet rule is to sample any lump that is pea-sized or larger and has been present for a month.
- Rapid growth, bleeding, ulceration, colour change, or a lump that is firm and fixed needs a prompt check.
- Pale-skinned cats and dogs need protection from strong sun to reduce skin cancer risk.
What a typical skin tag looks like
- Soft, small, and fleshy, often skin-coloured or slightly darker
- Hangs from a narrow stalk or sits as a small flap
- Moves with the skin and does not feel attached to deeper tissue
- Stays the same size over months
- Common on the chest, sides, legs, and around the face in older dogs
Other common benign lumps include warts (papillomas), fatty lumps (lipomas), sebaceous gland growths, and cysts.
Features that raise concern
- Growing quickly over days or weeks
- Changing colour, becoming dark, red, or patchy
- Bleeding, ulcerating, or scabbing without injury
- Firm, irregular, or fixed to underlying tissue
- Swelling and shrinking, or becoming itchy and red after being touched (a classic mast cell tumour feature)
- Sores that will not heal on the ear tips, nose, or eyelids of pale cats
- Any lump in the mouth, on a toe, or around the nail bed
Common skin cancers in pets
Mast cell tumours. The most common skin cancer in dogs. Boxers, pugs, Labradors, and Staffordshire bull terriers are among the breeds at higher risk. Behaviour ranges from low grade to aggressive. See mast cell tumours in dogs.
Squamous cell carcinoma. Linked to sun damage. In cats it often starts as reddening and crusting on white ear tips, the nose, or eyelids. In dogs it can appear on lightly pigmented belly skin.
Melanoma. Usually pigmented, though not always. Skin melanomas are often benign in dogs, but those in the mouth or nail bed are typically aggressive.
Soft tissue sarcomas. Firm lumps under the skin that may grow slowly and feel like fatty lumps.
What to do right now
- Measure the lump with a ruler and take a clear photo next to a coin for scale.
- Note where it is and when you first found it.
- Avoid squeezing, picking, or trying to tie off a skin tag at home. This can cause infection and, with mast cell tumours, release of inflammatory chemicals.
- Book a vet check. Bring your photos so changes can be tracked.
When to see a vet
Urgent, same day: a lump that is bleeding heavily, rapidly swelling, hot and painful, or accompanied by vomiting, lethargy, or not eating.
Within a week or two: any new lump pea-sized or bigger, any lump that has changed, a non-healing sore on a pale cat's ear or nose, or anything in the mouth or on a toe.
Routine check: a small, soft, unchanged skin tag. Mention it at your next visit, and keep monitoring.
How vets typically diagnose and treat
A fine needle aspirate collects cells with a thin needle, usually without sedation, and the cells are examined under a microscope. If this does not give a clear answer, a biopsy removes a piece of tissue for laboratory analysis. For confirmed cancers, vets may recommend blood tests, chest X-rays, ultrasound, or lymph node sampling to check for spread.
Benign tags may be left alone or removed if they catch, bleed, or bother your pet. Cancers are most often treated with surgical removal with a margin of healthy tissue. Depending on the type and grade, some pets also benefit from radiation, chemotherapy, or other therapies offered by veterinary oncologists.
Prevention and monitoring
- Do a monthly nose-to-tail lump check during grooming.
- Keep a simple lump map with dates and sizes.
- Keep white cats and pale dogs indoors in the middle of the day, and ask your vet about pet-safe sun protection.
- Keep up regular health checks, especially for older pets. See 13 signs of cancer in dogs.
FAQ
Can a skin tag turn into cancer?
True skin tags are benign and rarely change. The concern is that some cancers look like skin tags, which is why sampling is advised.
Is a needle sample painful?
Most pets tolerate it like a vaccination. Some lumps in sensitive areas may need light sedation.
Can I just watch a lump?
Monitoring alone is reasonable only once a vet has confirmed what it is. Unknown lumps should be sampled.
Are cats' lumps more worrying than dogs'?
In general, a higher proportion of skin lumps in cats are malignant, so new lumps in cats deserve prompt attention.
Talk with a vet
Photos and measurements can help a vet at Dial A Vet advise you how soon a lump should be checked in person. Only an in-clinic sample can confirm what it is.
References
- Merck Veterinary Manual. Tumours of the skin and soft tissues in dogs and cats.
- Veterinary Cancer Society. "See Something, Do Something" lump awareness campaign.
- Cornell Feline Health Center. Squamous cell carcinoma in cats.
- World Small Animal Veterinary Association (WSAVA). Oncology resources.
Disclaimer: Educational only. This page does not replace an examination by a veterinarian. Lumps cannot be diagnosed from appearance alone.
