What is a Mast Cell Tumour (MCT) in Dogs? Early Detection & What You Need to Know
Understand this common canine cancer through medical facts, expert veterinary guidance, and inspiration from Pimmy—a brave two-time MCT survivor.
A Note From Pimmy’s Mum: Why Early Detection Saved My Girl’s Life!
When I first found a small bump on Pimmy, it looked harmless—almost like a simple wart or lipoma. But because Mast Cell Tumours are known as "the great pretenders," we acted immediately. We are endlessly grateful to Dr. Diana Weir D.V.M. from Merivale Papanui Vets right here in Christchurch for her fast diagnostics, surgical expertise, and extraordinary care, along with our former Argentinian vet Dr. Analia Perez from Clínica Veterinaria VET for her guidance and ongoing support.
Catching her lump early and having our trusted vets perform a fine-needle aspiration saved Pimmy's life—not just once, but twice when a second tumour appeared. Proactive care and having a vet team you trust are your absolute best tools to protect your pup.
Pimmy’s Corner: "I’m a Two-Time MCT Warrior!" 🐾 Hey there, my furry friends! My journey, especially conquering two Mast Cell Tumours, taught me the true meaning of self-care and proactive love. Having my lumps checked by my wonderful doctors wasn't scary—it gave me and my parents the power to act fast! Now I’m bouncing, happy, and living my best life on a wholesome, plant-based diet packed with superfood veggies to keep me thriving. Don't let those pesky lumps hide—tell your humans to check your fur during snuggle time!""
What are Mast Cell Tumours in Dogs (MCT)?
How common are they?
MCTs are the most common skin tumours found in dogs, accounting for 7–21% of all skin cancer cases.
Where do they appear?
While most commonly found on or just under the skin, they can occasionally affect internal organs like the spleen, liver, or bone marrow.
Why are they called 'The Great Pretenders'?
MCTs rarely look like a typical dangerous mass. They easily mimic a bug bite, a harmless wart, an allergic reaction, or a benign lipoma (fatty bump).
MCTs can vary wildly in appearance—they may be raised, red, hairless, or ulcerated. A key sign is fluctuating size (growing and shrinking daily). This happens when the tumour is agitated and releases histamine (degranulation).
When degranulation occurs, the released chemicals can enter the bloodstream and cause secondary issues:
Digestive Upset: Vomiting, loss of appetite, and lethargy due to stomach ulcers.
Severe Reactions: In rare cases, a serious allergic reaction called anaphylaxis.
Internal Spread: Enlarged lymph nodes, spleen, or liver.
Key Warning Signs & High-Risk Breeds
While any dog can develop an MCT (typically older dogs around 8–9 years), certain breeds are more genetically predisposed:
Cocker Spaniels & Golden Retrievers
Boxers, Pugs, English Bulldogs & Boston Terriers
Staffordshire Terriers, Beagles & Labradors
Schnauzers, Rhodesian Ridgebacks, Weimaraners & Shar-Peis
Inspect your dog’s skin regularly. Book a vet visit immediately if you notice:
A New Mass: Any new lump or bump on or under the skin.
Changes in Existing Lumps: Rapid changes in size, color, texture, or swelling.
Irritation: A bump that looks red, swollen, hairless, or ulcerated.
Unexplained Illness: Secondary symptoms like vomiting or sudden lethargy.
Pimmy’s Corner: "High Risk? Who, Me?!" 🐾
"Okay, so, guess what? This super cute pup right here is a mix of Cocker Spaniel and Mini Golden Retriever! And get this—according to all the stuff my Mum and Dad have been reading, that means I'm double-likely to get those pesky MCTs. Ugh, right? Pfff!"
How Your Vet Diagnoses an MCT
You cannot diagnose a skin lump just by looking at it or feeling it! Your veterinarian will use:
Fine-Needle Aspiration (FNA): A quick, virtually painless in-clinic test where a small needle collects cells from the lump to view under a microscope.
Biopsy & Histopathology: Surgical removal and biopsy determine the tumour's grade (how aggressive it is) to guide the best treatment plan.
Pimmy’s Corner: "The Sneaky Fat Bump Trick!" 🐾 "Alright, so get this! This nasty MCT was playing tricks on us. My vet took a peek at first and was like, 'Oh, it looks like it might just be a little fat bump!' (Those harmless fat bumps are called Lipomas.) But you know my Mum and Dad—they wanted to be super sure! So the doctor did an FNA. Basically, poked it gently and sent the cells to the lab."
Understanding the Prognosis and Grading
Pathologists grade MCTs from Grade I to Grade III:
Grade I (Low-Grade): Less aggressive, high surgical success rate, low risk of spreading.
Grade III (High-Grade): Aggressive, higher risk of spreading (metastasizing) to other tissues.
Pimmy’s Corner: "The Phone Call That Changed Everything" 🐾
"Ugh, you guys, this part was the worst! Remember that FNA poke? It hadn't even been a week, and my Mum got a super sad phone call. The vet had the results: not good. I had an MCT on my chest! Mum was totally heartbroken and froze up.
Dad had to ditch work and zoom over to the vet to double-check everything and figure out what to do next. They scheduled my big surgery day for 29th July 2024! I had to do all this pre-surgery stuff—no munchies after 7:00 pm and barely any water in the morning. Then blood tests, waiting, and finally pickup at 4:00 pm. Talk about a wild ride!"
Pimmy's Story: Two Surgeries & Recovery
Pimmy is a proud double MCT survivor! Catching both lumps early and keeping a close relationship with our vet team made the recovery process smooth and manageable.
First Surgery: 29th July 2024 (Chest)
"Dr. Tim Nottage B.VSc, a super cool vet surgeon from Merivale Papanui Vet, did my first surgery! He was so nice to Mum and Dad, explained everything, and got clean margins. He suspected it was a Grade I tumour, but we had to wait two long weeks for the official lab biopsy. When the results came back, it was confirmed: Grade I and I was going to be all right! Yay!"
Second Surgery: 24th June 2026 (Neck)
"Just two years later, during my annual vaccine checkup, Dr. Diana Weir D.V.M from Merivale Papanui Vet, found a tiny new bump on my neck out of nowhere! We did another FNA, confirmed mast cells, and booked surgery 3 days later. Dr. Diana operated on me this time and got complete, clean margins! Once again, the lab confirmed a Grade I result. Brave pup victory!"
Treatment & Hope: Why There is Power in Action
Surgical removal with clear margins is the primary treatment for most localized MCTs and offers excellent long-term outcomes, especially when caught early.
Combined with expert veterinary care, supporting your dog with gentle, nutrient-dense nutrition, antioxidant-rich superfood veggies, and natural inflammation support provides a strong foundation for post-surgery wellness and vibrant ongoing health.
Found Hope in Pimmy’s Story? Help Us Spread the Light 🐾
Did you find Pimmy’s Mast Cell Tumour journey helpful or comforting? If her story offered a guiding hand during a scary time, consider supporting our mission to share early detection awareness with pet parents everywhere.
Coming Soon: Our Local Christchurch Giving Program
Once our oven timer rings and Pimmy’s Atelier officially opens, a set portion of proceeds from every single celebration cake sale will go directly to Dogwatch Sanctuary Trust right here in Christchurch. Your cake orders will directly help cover essential vet care, medical treatments, and food for shelter pups awaiting their forever homes.
Support Vital Canine Cancer Research Today
While we prepare for our grand opening, you can help make an immediate impact by supporting life-saving research directly:
In New Zealand: Donate to Massey University Veterinary Research
International: Donate to the National Canine Cancer Foundation
Every share, every check of your pup's skin, and every contribution brings us one step closer to a world with more early detection victories. Thank you for walking this path with us!
A Final Message From Our Family
We know firsthand how difficult a positive MCT diagnosis can be and how overwhelming it feels as a pet parent. The first step is to get support from your vet as soon as possible and ask as many questions as you need—no question is ever silly!
Stay calm and breathe, because your pup trusts you implicitly and senses your peace. Embrace this journey together, lean on your community, and ask for help. We send all our love and strength to you, and we trust Pimmy's story gives you hope, clarity, and resilience. ♥️♥️♥️♥️
Proactive Wellness Articles to Read Next:
A Little Note from Us: Before trying any new foods or implementing any health or treatment-related changes with your furry pal, it's always best to chat with your vet first. This blog shares some of Pimmy's favourite eats, which have played a big part in her recovery journey after her MCT experience and in keeping her feeling her best. We hope this information is helpful, but please remember it's not a substitute for professional vet or dietary advice. Sending lots of love to your pooch, cheers!
Sources: Information by VCA , Dog Cancer , Pet MD , Hill's Pet Nutrition, Small Door Veterinary
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