Mast cell tumors (MCTs) are the most common type of skin tumor in dogs, accounting for 7% to 21% of all skin cancers. These tumors arise from mast cells—immune cells involved in allergic reactions—and can cause a wide range of symptoms, from localized swelling to life-threatening metastasis.
Early diagnosis and appropriate treatment are key to improving your dog’s quality of life. In this article, you’ll learn everything you need to know about canine mast cell tumors: their causes, symptoms, diagnostic process, and available treatment options.
Which Dogs Are at Risk?
Although any dog can develop a mast cell tumor, certain breeds are more predisposed. Boxers, Labrador Retrievers, and Golden Retrievers are particularly at risk. The condition can affect dogs of any sex, and it typically appears in middle-aged to older pets.
Symptoms and Appearance
Mast cell tumors can vary greatly in appearance. They may present as:
- Single skin masses (sometimes hairless)
- Multiple inflamed lumps
- Masses that fluctuate in size
Around 10% of dogs diagnosed with an MCT will have multiple tumors or develop new ones later. The size of the tumor may change depending on mast cell degranulation, which releases histamine and other substances into the tissue.
Diagnosing a Mast Cell Tumor in Dogs
The primary method for diagnosing an MCT is cytology. This minimally invasive procedure uses a fine needle to extract cells from the mass for microscopic examination. Cytology provides a quick and low-stress confirmation of mast cell presence.
To assess tumor aggressiveness, veterinarians often use the Patnaik grading system, which classifies tumors as:
- Grade I: Least aggressive
- Grade II: Intermediate
- Grade III: Highly aggressive
Additional diagnostics such as blood tests, X-rays, and abdominal ultrasounds are often performed to detect potential metastasis, especially in the lymph nodes.
Treatment Options
The best treatment strategy depends on the tumor’s grade, size, and location. Common approaches include:
Surgery
Surgical excision is the first-line treatment for most mast cell tumors. The goal is to remove the mass along with a wide margin of healthy tissue to ensure complete removal. If cancerous cells remain near the edges, a second surgery may be recommended.
Radiation Therapy
Radiation therapy is particularly effective for:
- Incompletely removed tumors
- Grade I and II tumors
- Shrinking tumors before surgery
However, it does not prevent metastasis to distant organs.
Chemotherapy
Chemotherapy is generally reserved for:
- High-grade mast cell tumors
- Cases involving metastasis
- Situations where surgery isn’t possible
It may improve survival time, reduce tumor size, and enhance the dog’s quality of life.
Prognosis and Follow-Up
The prognosis depends largely on the tumor’s grade and how well it responds to treatment. Dogs with completely excised, low-grade tumors and no metastasis can often live normal lives. However, regular veterinary check-ups are essential, especially for dogs prone to tumor recurrence or metastasis
