Skin mass that's growing or changing on a dog
Any rapidly growing, ulcerating, or changing skin lump needs prompt vet review with fine-needle aspirate or biopsy — early diagnosis matters.
In the next 60 seconds
- Photograph and measure with date.
- Phone the vet for prompt appointment.
- Fit a buster collar if the dog is licking or chewing the lump.
Recognise the signs
- Lump growing rapidly
- Lump changing in size from day to day (classic mast cell tumour)
- Ulceration, bleeding, foul smell
- Lump that's firm, fixed, or invasive
First aid steps
- Photograph and measure with date.
- Phone the vet for prompt appointment.
- Fit a buster collar if the dog is licking or chewing the lump.
Do NOT
- Do not delay — early diagnosis often allows curative surgery.
- Do not squeeze or apply creams.
- Do not rely on appearance alone — fine-needle aspirate is essential.
When to phone the vet immediately
- Rapid growth
- Ulceration, bleeding, smell
- Dog unwell systemically
Common causes
- Mast cell tumour (variable in appearance)
- Soft tissue sarcoma
- Other tumours
- Histiocytoma (young dogs, often regresses spontaneously)
- Reactive lump (insect, infection)
What you'll need
As an Amazon Associate we earn from qualifying purchases — at no extra cost to you. Links are affiliate links.
-
Amazon
If a mass becomes ulcerated or bleeds between appointments, having saline and clean dressings to hand helps you manage it safely until the vet can see it.
Check Price on Amazon →
What the vet will need to know
- When first noticed
- Growth rate
- Photo timeline
- Other lumps
Aftercare
- Fine-needle aspirate, biopsy, or excision and biopsy.
- Surgery, sometimes with radiotherapy or chemotherapy depending on type.
- Regular monitoring for recurrence or new masses.
Prevention
- Regular grooming with hands-on body checks.
- Annual exams catch many lumps early.
Breed-specific notes
- Mast cell tumour: Boxer, Bulldog, Boston Terrier, Pug, Labrador, Golden Retriever.
Frequently asked questions
Could a fast-growing lump be benign?
Possibly — abscesses and inflammatory lumps grow fast too. Aspirate distinguishes.
Should I just have any lump removed?
Aspirate first to characterise. Some lumps need wide-margin removal; others can be safely monitored.
Will my dog need chemotherapy?
Depends on tumour type, grade, and stage. Many cancers in dogs respond well to surgery alone or with adjunctive therapy.
Vet-prescribed treatments delivered to your door
Prescription and over-the-counter treatments from a licensed UK veterinary pharmacy — flea, tick, worm, skin and wound care for dogs and cats.
Affiliate link — we may earn a commission at no extra cost to you. Supplied by Best Vet Care (licensed UK veterinary pharmacy).
Browse Best Vet Care →