By Courtney Prue | July 14, 2025

Mast Cell Tumours In Dogs: Symptoms, Causes, And Treatment

What are mast cell tumours in dogs? 

Mast cell tumours are a type of cancer that can develop in dogs. These tumours can grow in any part of the body, including the skin, spleen, liver, and bone marrow. Mast cells are immune cells that play a crucial role in the body’s inflammatory response. However, in dogs with mast cell tumours, these usually normal cells can become malignant, leading to the development of cancerous tumours.

What causes mast cell tumours in dogs to become cancerous?

The exact cause of mast cell tumours in dogs is unknown. However, certain breeds, including Boxers, Boston Terriers, Labrador Retrievers, and Golden Retrievers, are more prone to developing these tumours. Additionally, exposure to certain environmental factors may increase the risk of developing mast cell tumours.

How do I know if my dog has mast cell cancer?

The symptoms of mast cell tumours can vary depending on the location and stage of the tumour. 

Common symptoms include:

• A lump or bump on the skin that may be red, swollen, or itchy
• Loss of appetite
• Vomiting and diarrhea
• Lethargy
• Rapid weight loss
• Difficulty breathing
• Swollen lymph nodes

Is a mast cell tumour ever an emergency?

It’s important for dog owners to be aware of the signs of an emergency related to their pet’s health, especially when dealing with conditions like mast cell tumours. In some cases, a sudden and severe reaction can occur, which requires immediate medical attention. Here are some signs that may indicate an emergency related to a mast cell tumour:

• Rapid swelling: If the tumour suddenly starts to rapidly grow or expand, it can cause significant swelling in the affected area. This can be a sign of a severe reaction and should be evaluated by a veterinarian immediately.
• Difficulty breathing: Mast cell tumours can affect the respiratory system, and in some cases, they can cause difficulty breathing or shortness of breath. If your dog is struggling to breathe, it’s essential to seek emergency care as soon as possible.
• Pale gums: In some cases, mast cell tumours can lead to internal bleeding, which can cause the gums to become pale or white. This can be a sign of a severe reaction and should be evaluated by a veterinarian immediately.
• Lethargy: If your dog suddenly becomes lethargic, weak, or unresponsive, it could be a sign of a severe reaction to a mast cell tumour. It’s important to seek emergency medical care as soon as possible in these situations.
• Vomiting and diarrhoea: Mast cell tumours can cause gastrointestinal symptoms, including vomiting and diarrhoea. If your dog is experiencing severe or persistent vomiting and/or diarrhoea, it’s essential to seek emergency care.

If you observe any of these symptoms, seeking immediate veterinary attention is important. Time is critical in emergency situations, and a delay in treatment can have serious consequences for your dog’s health. Don’t hesitate to call your veterinarian, our team or an emergency veterinary clinic for guidance on how to proceed.

How are mast cell tumours in dogs diagnosed?

If you find a lump on your dog or are worried about swelling or a decline in health, your veterinarian will perform diagnostic tests, including:

• Fine needle aspiration or biopsy of the lump, which can either be examined at the clinic by your veterinarian, or sent off to an external pathologist to review and diagnose.
• Blood tests to evaluate liver and kidney function
• Imaging tests such as X-rays or ultrasounds to check for the spread of cancer
• If your veterinarian surgically removes the lump, it may be sent off for histopathology, which is a diagnostic test that diagnoses the type of mass, if it is malignant or benign, if the whole mass has been removed, and how aggressive it is likely to be.

What are the treatment options for mast cell cancer in dogs?

The treatment options for mast cell tumours will depend on the tumour’s location, size, and stage. Common treatment options include:

• Surgical removal of the mass: In general, surgery is the primary treatment for mast cell tumours. The goal of surgery is to remove the tumour completely, along with a wide margin of normal tissue to ensure that all cancer cells have been removed.
• If the tumour is in a difficult location, if surgery cannot remove the entire tumour, or if the tumour has spread to other locations additional treatments may be necessary. These additional treatments require referral to an oncologist at a specialist centre. 
  • Radiation therapy: Radiation therapy uses high-energy radiation to kill cancer cells. It is often used after surgery to eliminate any remaining cancer cells in the surrounding tissue.
  • Chemotherapy: Chemotherapy involves the use of drugs that kill cancer cells throughout the body. It is often used in cases where the cancer has spread to other parts of the body.
  • Immunotherapy: Immunotherapy is a relatively new treatment option for mast cell tumours in dogs. This type of therapy works by harnessing the power of the dog’s immune system to fight cancer cells. In essence, immunotherapy aims to help the immune system recognise and attack the tumour cells more effectively.

The medical management and treatment options can be confusing and overwhelming. Get in touch with our team today for a personalised discussion. 

How can I help my dog with mast cell cancer at home? 

In addition to medical treatment, there are several steps you can take to optimise your dog’s care at home. These include:

• Keeping your dog’s environment clean and free of potential irritants
• Providing a healthy and balanced diet
• Monitoring your dog’s behaviour and symptoms for any changes
• Administering medications as prescribed by your veterinarian
• Consider palliative care to maximise comfort for as long as possible

An in-home veterinary assessment can also be helpful to identify any other areas of improvement, that can help your beloved pet stay comfortable for as long as possible. 

What is the survival rate for mast cell tumours in dogs? 

The prognosis for dogs with mast cell tumours will depend on several factors, including the grade of the tumour, the location, and the effectiveness of treatment. Some dogs may be cured with surgery alone, while others may require additional treatment such as radiation or chemotherapy.  If they seem increasingly uncomfortable or their quality of life is impacted, palliative care may be the kindest option. 

End-of-life care tips

If your dog’s mast cell tumour has progressed to a point where treatment is no longer effective or its symptoms are too severe, it’s important to consider end-of-life care options, including possibly putting your dog to sleep (euthanasia). Rest Your Paws is here to support you and provide compassionate care for your beloved pet throughout their journey. Here are some end-of-life care tips for dogs with cancers such as mast cell tumours:

• Keep them comfortable and well-nourished with food that they enjoy
• Spend quality time with them, making the most of every moment, such as with a bucket list.
• Offer a peaceful and stress-free environment, free from triggers that can exacerbate symptoms
• Administer medications as prescribed for pain management and symptom relief
• Provide a warm and comfortable space for your dog to rest and sleep, with easy access to food, water, and a place to relieve themselves
• Monitor your dog’s breathing, heart rate, and overall condition, and seek veterinary attention if necessary
• Evaluate their pain regularly and work with your veterinarian or our team to reduce pain.
• Evaluate their quality of life regularly, or reach out to a palliative care vet to help you with this. 
• Consult our End of Life Care Pack to get prepared to put your dog to sleep.
• Track good days and bad days on our Quality of Life Assessment Calendar.

Please know that we are here to support you every step of the way. We understand that this is a challenging time for you and your family, and we are committed to providing you with the guidance and care that you and your furry friend deserve. If you want to learn more about putting your pet to sleep, dog euthanasia at home, options to put your pet down at home, costs of euthanasia at home or what it looks like to put your pet to sleep at home, call us on 0422 157 675 or visit our website.

We understand that the diagnosis of mast cell tumours in your dog can be a challenging and emotional experience. However, with early diagnosis and proper treatment, your furry friend can lead a comfortable and happy life for as long as possible. At Rest Your Paws, we are committed to providing compassionate care and support to both you and your pet during this difficult time. We hope this resource has provided you with useful information on mast cell tumours and has given you a better understanding of how to optimise your dog’s care. Remember, we are always here for you and your furry friend. Please do not hesitate to reach out to us if you have any questions or concerns – we are here to help.

Rest Your Paws

We offer in-home pet euthanasia for dogs and cats. Say goodbye with peace and dignity to your beloved pet. Professional and experienced end-of-life support.