Mastocytoma in dogs (canine mastocytoma) is one of the most common skin tumors. Many owners first notice what seems like a harmless small lump on the dog’s skin, but it often means much more. That is why it is important to recognize the symptoms in time and understand how the disease can be treated.
What are mast cells?
Mast cells, or mastocytes, are special white blood cells that play a role in proper immune response. They are present in most tissues of the body but are found in higher numbers at the interface between the external and internal environments. For example, the skin, mucous membranes (respiratory tract, digestive tract), conjunctiva, and nose. They participate in immune responses against bacteria and multicellular parasites, in wound healing, and they are also the main effector cells in allergic processes.
Why can mast cells become a problem?
When the body is exposed to various harmful effects, mast cells produce substances such as histamine. Histamine triggers a reaction similar to allergy symptoms, which “alerts” the immune system. Although these compounds are essential for the body’s normal function, particularly in proper immune response, their overproduction can cause serious problems.
Symptoms of mastocytoma in dogs
Unfortunately, the exact causes of mastocytoma in dogs are still unknown. It is one of the most common types of skin cancer in dogs. About one-third of canine cancers are skin cancers, and mast cell tumors account for around 20% of them.
It can occur in dogs of any age, sex, or breed, anywhere on the body. However, certain breeds seem to be predisposed to this type of tumor (Beagle, Boston Terrier, Staffordshire Terrier, Fox Terrier, Bulldog, Bullmastiff, Dachshund, Labrador, Schnauzer, American Staffordshire Terrier, Golden Retriever). The likelihood increases with age, usually from 8–9 years onward.
The most typical sign of mastocytoma, or mast cell tumor in dogs, is a growth on the skin’s surface. The growth can look very different, from a wart-like bump to an ulcerated sore. Most often, they appear alone, but sometimes several develop side by side, usually on the trunk and limbs, less commonly on the head and neck. Another hallmark of mastocytoma is the size fluctuation of the lump – it may grow or shrink from day to day. The tumors are usually not painful, but if they are very swollen or ulcerated, they can become painful.
Owners often describe the tumor as a lump that “changes size from day to day.” This phenomenon is highly characteristic of mastocytoma in dogs and often draws attention to the problem for the first time.
Systemic symptoms of mastocytoma in dogs
Depending on the tumor’s location and size, the dog may experience loss of appetite, vomiting, or even bloody vomit. It can also cause diarrhea and abdominal pain, while dark or black stool may appear because of internal bleeding. In addition, itching and lethargy are common, and some dogs develop coughing and difficulty breathing. The disease can also lead to irregular heart rhythm and blood pressure, and it may result in various bleeding disorders. Finally, delayed wound healing and enlarged lymph nodes often occur as further signs of the condition.
Treatment of mastocytoma in dogs
Veterinarians most often treat mastocytoma in dogs by surgically removing the tumor, provided it is well-defined. During the procedure, they usually remove not only the tumor but also some of the surrounding healthy tissue to ensure a successful outcome. Because this type of tumor spreads quickly and insidiously, veterinarians often follow surgery with chemotherapy or radiation therapy to destroy any remaining tumor cells.
Surgery and chemotherapy effectively remove most of the tumor, but this is only half of the healing process. These treatments do not cure cancer, nor do they correct the malfunctioning of the immune system that allowed the tumor cells to develop.
However, when surgery and chemotherapy remove the bulk of the tumor cells, which place a heavy burden on the body, and at the same time immunomodulatory therapy (K9 INU® and K9 INUExtra®) stimulates the body’s defense system, the chances of overcoming the tumor and achieving a normal lifespan are excellent.
Strengthening the immune system is essential not only against mastocytoma in dogs but also against other cancers (lymphoma, osteosarcoma, dog brain tumor, hemangiosarcoma, mammary tumors, etc.), as well as other immune-related disorders. Without the body’s own response, there is no real healing, only symptomatic treatment.
That is why many veterinarians rightly say that life can only be prolonged, but the tumor remains. Surgery and radiation therapy are essential to remove the already developed tumor, but the dog’s own immune strength is necessary to truly fight the disease.
It is crucial to place strong emphasis on boosting the immune system alongside veterinary treatments!
The importance of immunomodulatory therapy
Alongside surgical and oncological interventions, immunomodulatory therapy is gaining increasing importance. Instead of directly destroying tumor cells, it activates and strengthens the dog’s own immune system. The goal is for the body to recognize and control tumor cells over the long term.
Immunomodulatory supplements such as K9 INU® or K9 INUExtra® use mushroom extracts and other natural ingredients to support cell-level immune response, reduce inflammation, and help prevent tumor recurrence.
The right diet is essential
Cancer is one of the most common causes of death in dogs. According to many experts, an improper diet can significantly contribute to the development of cancer. Dogs are often fed kibble and foods based on grains, even though they do not graze in wheat fields in nature. Their digestive system is not designed to process grains efficiently, as they are essentially carnivores.
If a carnivorous animal lives long-term on a grain-based diet, its body does not receive sufficient, highly usable nutrients. This increases the likelihood of immune disorders, which can also raise the risk of cancer.
Practical advice: Provide a protein-rich, meat-based diet, supplemented with vegetables and omega-3 fatty acids (K9 INUKrill®). These support immune function and may reduce inflammation.
Below we have collected the most common questions from dog owners about mastocytoma in dogs, to give you quick and clear answers to the most important issues.
Frequently asked questions about mastocytoma in dogs
Understanding mastocytoma in dogs
❓ What is mastocytoma in dogs?
Mastocytoma, also called mast cell tumor in dogs, develops from mast cells, and these cells are normally part of the immune system. However, when they start to grow uncontrollably, they form lumps or masses on the skin or mucous membranes, so the disease becomes noticeable.
❓ What symptoms can mastocytoma cause in dogs?
One or more skin lumps usually appear, and they may look wart-like, ulcerated, red, or swollen. In addition, other signs such as loss of appetite, vomiting, diarrhea, and enlarged lymph nodes can also occur, and together these symptoms make the condition easier to identify.
Pain, breeds, and diagnosis
❓ Is mastocytoma painful in dogs?
Most mastocytomas are not painful, especially in the early stages, but if the tumor ulcerates or becomes inflamed, it can cause sensitivity and discomfort. Therefore, pain may not appear at first, yet it often increases as the tumor progresses.
❓ Which dog breeds are more prone to mastocytoma?
Mastocytoma can occur in any breed, but Boxers, Bulldogs, Labradors, Beagles, Staffordshire Terriers, and Golden Retrievers are more commonly affected. Moreover, the disease is more frequent in older dogs, and age often increases the risk of developing it.
❓ How is mastocytoma diagnosed?
A veterinarian may perform cytology, such as fine-needle aspiration, or histology, and both tests are reliable. These methods not only confirm if the tumor originates from mast cells, but they also help assess the aggressiveness of the cancer, so treatment can be planned more effectively.
Treatment, prognosis, and home care
❓ What treatment options are available for mastocytoma in dogs?
The most common treatment is surgical removal of the tumor, and in many cases chemotherapy or radiation therapy is also required. In addition, immunomodulatory therapy can strengthen the immune system and reduce the risk of recurrence, so it serves as an important complement to standard treatments.
❓ What is the prognosis for mastocytoma in dogs?
The prognosis depends on the type, size, and location of the tumor, and early treatment greatly improves the chances of success. With timely surgery and proper follow-up care, many dogs can remain symptom-free for a long time, although regular check-ups are still essential.
❓ What can I do at home if my dog has mastocytoma?
Regular veterinary check-ups and sticking to the treatment plan are essential, while supporting the immune system makes recovery more effective. In addition, provide a calm and stress-free environment, and make sure to include a balanced diet with immune-boosting supplements, because these steps together help your dog regain strength and well-being.
More about canine tumors
- Osteosarcoma in dogs
- Hemangiosarcoma in dogs
- Lymphoma in dogs
- Dog mammary tumor
- Brain tumors in dogs
Click the link if you would like to read more about masztocitoma kutyáknál. You can find more facts about dog tumor types and about medicinal mushrooms. For more information, you can read our article on feeding dogs with cancer, or browse our immune-boosting supplements for dogs.
Important: the above information is for educational purposes only and does not replace veterinary consultation. If you notice any suspicious lump or change on your dog, visit your veterinarian as soon as possible.
References:
- de Nardi, A. B., et al. (2022). Diagnosis, prognosis and treatment of canine cutaneous and subcutaneous mast cell tumors: A review after the second consensus meeting. Animals.
- Garrett, L. D. (2014). Canine mast cell tumors: Diagnosis, treatment, and prognosis. Open Veterinary Journal.
- Ilyinskaya, G. V., et al. (2018). Oncolytic Sendai virus therapy of canine mast cell tumors: A pilot study. Viruses.
- Ong, S. M., McKenna, C., & Oblak, M. L. (2025). Clinical outcomes of dogs with high-grade cutaneous mast cell tumors. Frontiers in Veterinary Science, 11, 1519636.
- Hampel, J. M. (2024). The promise of immunotherapeutic strategies to advance canine cancer medicine. Journal of the American Veterinary Medical Association.
