---
title: "Mast Cell Tumours in Dogs UK"
description: "Mast cell tumours are common skin cancers in UK dogs. Learn how to spot lumps, grading, surgery and when to see your vet urgently."
url: "https://pethealth.org.uk/health/mast-cell-tumours-dogs-uk"
canonical: "https://pethealth.org.uk/health/mast-cell-tumours-dogs-uk"
date_published: "2026-06-25"
date_modified: "2026-06-25"
source: "PETHEALTH+"
---

# Mast Cell Tumours in Dogs UK

**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.

## What mast cell tumours look like

MCTs are unpredictable in appearance. They may present as:

- A raised, hairless lump on the skin
- A flat, reddened patch
- A lump that suddenly swells or shrinks
- A lump that looks identical to a benign fatty mass

Breeds with higher risk include Boxers, Bulldogs, Golden Retrievers, Labrador Retrievers and Shar-Peis — though any dog can develop MCTs.

## Why mast cell tumours are concerning

Mast cells contain histamine and other chemicals. When disturbed — during handling, biopsy or surgery — they can release these substances, causing:

- Sudden lump swelling
- Vomiting or diarrhoea
- Facial swelling
- Low blood pressure (rare but serious)

This is why vets often give antihistamines and stomach protectants before and after surgical removal.

## Diagnosis and grading

Your vet will typically perform **fine-needle aspiration** (FNA) — a quick test that examines cells under a microscope. If MCT is suspected, the lump is surgically removed and sent for **histopathology grading** (often Patnaik or Kiupel grading).

| Grade | Behaviour |
|-------|-----------|
| Low grade | Slow growth; wide surgical removal often curative |
| High grade | More likely to spread; may need chemotherapy |

Chest X-rays and abdominal ultrasound may be recommended for high-grade tumours to check for spread.

## Treatment options

- **Surgical excision** — primary treatment; wide margins improve outcomes
- **Chemotherapy** — for high-grade or metastatic disease
- **Radiation** — when complete surgical removal is not possible
- **Palliative care** — antihistamines and pain relief for advanced cases

Early removal of small lumps generally gives the best prognosis. Delay allows tumours to grow and makes complete excision harder.

## When to see your vet

Book an appointment within days for any new lump. Seek urgent care if a lump swells suddenly, your dog vomits after the lump is touched, or a known lump grows rapidly.

Check your dog's skin monthly — run your hands over the body, including under the fur and between toes.

## FAQs

### 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.

### Can mast cell tumours be cured in dogs?

Low-grade tumours removed early with wide surgical margins often have excellent outcomes. High-grade tumours may need additional chemotherapy or radiation — prognosis varies by grade and location.

## Sources

- [Blue Cross — Lumps on dogs](https://www.bluecross.org.uk/pet-advice)
- [PDSA — Cancer in dogs](https://www.pdsa.org.uk/pet-help-and-advice/pet-health-hub)
- [BVA — Advice for pet owners](https://www.bva.co.uk)

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Last modified: 2026-06-25