Understanding Mast Cell Tumors in Dogs and Cats: A Guide for Pet Owners

At College Hills Veterinary Hospital, we understand the deep bond you share with your pets. We know their health and well-being are important to you. As a pet owner, being informed about common health issues that may affect your beloved furry companions is crucial. One such concern is mast cell tumors (MCTs), which can occur in dogs and cats. In this blog, we will provide information on mast cell tumors in dogs and cats so you can be alert to symptoms and understand why early detection and treatment are crucial to giving your pet the best prognosis.

What Are Normal Mast Cells?

Normal mast cells are white blood cells vital to the body’s immune system. They are typically found in connective tissue throughout the body, particularly in the skin, respiratory tract, and digestive system.

When the body encounters something it perceives as harmful, like an allergen or infection, mast cells release substances such as histamine. These substances trigger inflammation and other immune responses to help the body defend itself. Think of mast cells as the body’s first responders to potential threats, helping to initiate the immune response to protect against invaders.

What Are Mast Cell Tumors?

Mast cell tumors are abnormal growths that develop from mast cells. They can manifest anywhere on a pet’s body and vary in size, shape, and severity. While any dog or cat can get a mast cell tumor, certain breeds may be predisposed to this condition.

  • Boxers
  • Boston terriers
  • Pugs
  • Bullmastiffs
  • Cocker spaniels
  • Bull terriers
  • Staffordshire terriers
  • Fox terriers
  • Labrador retrievers
  • Golden retrievers
  • Beagles
  • Schnauzers
  • Weimaraners

As with dogs, any cat can get a mast cell tumor, but Siamese breeds are predisposed to these tumors.

Signs and Symptoms

Early detection of mast cell tumors early is essential for effective treatment. Some common signs and symptoms of MCTs to look for in pets include:

  • Visible Lumps or Bumps: These may appear as raised masses on the skin. Regularly check your pet for unusual lumps, bumps, or growths during grooming sessions or cuddle time.
  • Skin Irritation or Inflammation: MCTs can cause the surrounding skin to become red, swollen, itchy, or ulcerated. Pay attention to any changes in your pet’s skin texture or appearance.
  • Gastrointestinal Symptoms: In some cases, internal MCTs can lead to vomiting, diarrhea, or loss of appetite.

Diagnosis and Treatment

If you notice any concerning signs, it’s vital to consult with your veterinarian at College Hills promptly. Diagnosing MCTs often involves a combination of physical examination, fine-needle aspiration, and biopsy to confirm the presence of cancerous cells. Further tests, such as bloodwork or imaging studies, may be recommended to assess the extent of the disease.

Treatment options for mast cell tumors in pets vary depending on the tumor’s location, size, and grade. Common approaches include:


Surgical removal of the tumor is often recommended, especially for localized MCTs. After we surgically remove your pet’s tumor, we send it to a lab for evaluation. If the lab reports that all the edges are clear of cancer cells, we refer to the tumor as having “clear margins.” Clear margins mean that during surgery, we were able to remove the cancer along with a bit of healthy tissue around it, and upon examination, there’s no evidence of cancer cells left behind at the edges. This news is positive as it suggests that we removed the tumor completely, reducing the chances of it coming back. We may not recommend further treatment in this case but will likely need to monitor your pet closely to ensure no recurrence. But, if we find cancer cells near the edges, your pet might need more surgery, radiation, or chemotherapy to make sure all the cancer is gone.


We may recommend chemotherapy for aggressive MCTs or those that have spread to other parts of the body, aiming to shrink tumors and prevent metastasis. Metastasis is when cancer cells spread to other parts of the body. When cancer cells break away from the primary tumor, they can travel to other organs or tissues to form new tumors. This is a significant concern because it can make cancer more difficult to treat and can affect the patient’s prognosis or outcome.

Radiation Therapy

This therapy is used in conjunction with surgery or as a standalone therapy for MCTs that are not amenable to surgical removal.

Supportive Care

We may prescribe medications to manage pain, itching, or gastrointestinal upset associated with MCTs

Prognosis and Long-Term Management

The prognosis for pets with mast cell tumors varies depending on factors such as the tumor’s grade, stage, and response to treatment. Regular follow-up appointments with your veterinarian are essential to monitor your pet’s progress and detect any signs of recurrence or complications. Maintaining a healthy lifestyle, including a balanced diet, regular exercise, and preventive care, can contribute to their overall well-being and potentially reduce the risk of MCT development or recurrence.

Are All Lumps or Bumps Mast Cell Tumors?

When you find a lump, bump, or growth on your pet, your first impulse might be to think that it’s cancer and panic. However, some are benign (non-cancerous) and easily removed. For more information on benign tumors, please see our blog: What are These Lumps, Bumps, and Growths on My Pet.

Getting any lump or bump on your pet checked out by a veterinarian is crucial because while some may not be cancerous, others could be. Even non-cancerous lumps or bumps can still indicate health issues or discomfort for your pet. Additionally, some benign lumps could turn cancerous over time if left untreated. Early detection and proper diagnosis by a veterinarian are essential for determining the nature of the lump or bump and developing an appropriate treatment plan to ensure your pet’s well-being.

Conclusion: Take Action Against Tumors

While finding a lump, bump, or growth on your pet is concerning, timely intervention and appropriate veterinary care can significantly affect their prognosis and quality of life. Our dedicated College Hills Veterinary Hospital team is committed to providing compassionate and comprehensive care for pets facing health challenges like MCTs. By staying informed and proactive, you can help ensure your furry companion’s bright and healthy future

Warm regards,

College Hills Veterinary Hospital

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