A–Z topic · M
Mast cell tumours
Quick answer
**Mast cell tumours (MCTs)** are among the most common skin cancers in UK dogs. They can look harmless but behave unpredictably — some are benign after removal, others spread aggressively. **Any new lump needs a vet check**; never assume a lump is "just a fatty lump" without testing.
Key takeaways
- A mast cell tumour (MCT) is a cancer arising from mast cells in the skin or internal organs. They vary from low-grade lumps to aggressive cancers that spread.
- You cannot tell by appearance alone. Any new lump, or a lump that changes size, should be checked by your vet. Fine-needle aspiration or biopsy confirms the diagnosis.
- They can release histamine, causing swelling, itching, stomach upset or sudden lump size changes. Some dogs show no discomfort until the tumour grows large.
The full guide
Causes, symptoms, treatment options and when to call your vet — in the complete plain-English guide.
Frequently Asked Questions
- What is a mast cell tumour in dogs?
- A mast cell tumour (MCT) is a cancer arising from mast cells in the skin or internal organs. They vary from low-grade lumps to aggressive cancers that spread.
- How do I know if my dog's lump is a mast cell tumour?
- You cannot tell by appearance alone. Any new lump, or a lump that changes size, should be checked by your vet. Fine-needle aspiration or biopsy confirms the diagnosis.
- Are mast cell tumours painful for dogs?
- They can release histamine, causing swelling, itching, stomach upset or sudden lump size changes. Some dogs show no discomfort until the tumour grows large.