Mast Cell Tumors in Dogs – Causes, Symptoms, Diagnostic Methods, Treatments, and Tips for Improvement and CureImprovement Methods for Mast Cell Tumors

What kind of cancer is mast cell tumor in dogs?

What are mast cells?

Mast cells are named because they appear swollen and fat under a microscope.

Mast cells are a type of white blood cell that releases a substance called histamine. Histamine is involved in inflammation and immune responses and also affects the functioning of internal organs.

Although histamine may have a negative image due to its role in allergic reactions, such as causing symptoms in hay fever, it is actually a defense mechanism to expel foreign substances from the body. The body is protected by the function of mast cells.

It should be noted that adipocytes, which store fat within the cell, are related to obesity, but they have no direct connection with mast cells or mast cell tumors.

What is a mast cell tumor?

Mast cell tumors can occur in the skin or internal organs, but in dogs, they most commonly occur in the skin, making it the most common malignant tumor found in canine skin.

Although the name mast cell tumor might suggest a connection with obesity, there is no direct link between the two.

The image above is an ultrasound scan of a mast cell tumor. The drawing below is one used by veterinarians to explain to patients.

When a lump on the skin or internal organs is identified as a mast cell tumor, there is a high possibility it is malignant and therefore cancerous.

Due to the risk of spread or metastasis, it should be surgically removed promptly. However, because mast cell tumors have a high malignancy rate, a wide-margin excision, or ‘radical surgery‘ is necessary. Depending on the location, it might be challenging to secure adequate margins, and even if it appears to have been completely removed, recurrence or metastasis is not uncommon.

If surgery successfully removes the mast cell tumor without recurrence or metastasis, it is ideal. However, if it metastasizes and spreads to other organs or the entire body, it could cause issues such as gastrointestinal inflammation or bleeding, leading to blood in vomit or stools. Appetite loss and a decline in energy and appetite may also be observed.
Mast cell tumors are a type of malignant tumor, but early detection and prompt treatment can significantly improve the chances of recovery. Therefore, if you notice any abnormalities on your pet’s skin, please visit an animal hospital as soon as possible.

Symptoms when a dog has a mast cell tumor

Mast cell tumors in dogs can present in various shapes, ranging from hard lumps to soft fatty masses, or as nodules that either protrude like warts or spread flat across the skin. Due to this variation, it is necessary to undergo tests at an animal hospital to determine whether a lump is a mast cell tumor.

In mast cell tumors, substances like histamine are released in large quantities. While histamine is essential for life, excessive amounts can cause various issues such as increased susceptibility to allergic reactions, increased gastric acid leading to ulcers, and respiratory difficulties due to lung impairment. These issues can greatly reduce the quality of life (QOL) and, in severe cases, endanger life.

If pet owners notice changes in their dog’s appearance or health, they should visit an animal hospital as soon as possible and undergo necessary tests.

Symptoms when a mast cell tumor occurs on the skin

Most mast cell tumors in dogs develop on the skin. Approximately 50% occur on the trunk and genital area, 40% on the limbs, and 10% on the head and neck. Hair loss in these areas may also be an indicator.

When a lump develops on the dog’s skin and becomes inflamed, it might indicate a high degree of malignancy. If there is inflammation or bleeding from the lump, prompt examination by a veterinarian is recommended.

Other tumors found on the skin

Other types of skin cancer include melanoma and squamous cell carcinoma.

Symptoms when a mast cell tumor occurs in internal organs

Mast cell tumors can also be found in internal organs. Most cases in internal organs are considered to be metastases from the skin. Metastasis commonly occurs in lymph nodes, liver, spleen, and bone marrow.

When a mast cell tumor develops in internal organs, symptoms such as nausea and loss of appetite become prominent. There may be bloody stools due to internal bleeding, leading to anemia, and sometimes difficulty in defecation.

Causes of Mast Cell Tumors

Mast Cell Tumors (MCTs) can occur regardless of age or breed, and therefore, the exact cause of MCTs is still unknown.

Generally, genetic factors, a decline in immune function due to aging, lifestyle problems such as diet, environmental pollution, and stress are considered potential causes of MCTs.

MCTs tend to be more common in breeds such as Labrador Retrievers, Golden Retrievers, short-headed breeds like Pugs, Boxers, Bulldogs, but other breeds are also susceptible to MCTs.

Tests When MCTs Are Suspected

Cytology

Cytology involves using a needle to collect cells from the suspected MCT area and examining them under a microscope. This method is mostly painless and can be easily performed without anesthesia. However, as cytology yields a small number of cells, it sometimes fails to provide an accurate diagnosis.

Blood Tests

When MCTs are suspected, blood tests are conducted to check for anemia, assess internal organ function, and measure changes in histamine levels released by the MCTs.

Imaging Tests (X-ray, CT, MRI, etc.)

To check if the cancer has spread to internal organs or lymph nodes in areas such as the chest or abdomen, imaging tests like X-rays, CT scans, and MRI are performed. While imaging results alone cannot determine the type of tumor, a definitive diagnosis requires tissue biopsy or cytology.

Genetic Testing

Genetic testing, which involves collecting a small number of cells, can help determine the type of MCT. It is useful for predicting malignancy and the efficacy of certain treatments.

Grading MCTs (Malignancy Level)

All MCTs are malignant tumors (cancer), but they can be divided into three levels of malignancy, with treatment methods varying by severity. MCTs that develop outside the skin are treated as highly malignant.

Mast cell tumors graded as level 2 or 3 might be said to be difficult to completely cure. However, significant improvement in prognosis is not impossible with appropriate efforts. I will explain the methods later.

Treatment of Canine Mast Cell Tumors

Treatment for Canine Mast Cell Tumors: Surgery

The primary treatment prioritized when a dog has a mast cell tumor is surgery. The tumor is excised as broadly as possible, including the surrounding area (wide excision). This is because leaving behind any mast cells (cancerous cells) can easily lead to recurrence. If recurrence occurs, it is generally considered extremely difficult to cure.

Even when it is known that the tumor cannot be completely removed, surgery is sometimes performed. Since a large amount of histamine and other substances are released from mast cell tumors, it can cause physical discomfort. By reducing the tumor through surgery, symptoms may be alleviated. Incidentally, surgery performed with the aim of symptom relief is called palliative surgery.

Treatment for Canine Mast Cell Tumors: Chemotherapy / Targeted Therapy

Chemotherapy (treatment with anticancer drugs) may be utilized as a treatment for mast cell tumors. Since anticancer drugs act on the entire body, they are suitable for cases where the tumor has spread too widely to be completely removed by surgery. However, it is challenging to cure mast cell tumors with chemotherapy alone. Moreover, there is a possibility of severe side effects, which must be anticipated.

Targeted therapies such as Imatinib or Palladia (Toceranib) are also used for treating mast cell tumors.

Targeted therapies are said to have fewer side effects compared to conventional anticancer drugs as they inhibit specific tumor cells, but they can still cause side effects such as gastrointestinal disorders or interstitial pneumonia, so you should monitor your dog closely when using them.

Palladia is expected to lead to direct inhibition of tumor growth by suppressing the function of specific molecules, as well as indirectly inhibiting tumor growth by preventing the formation of blood vessels necessary for tumor expansion. However, it causes gastrointestinal side effects (vomiting or loss of appetite) more frequently than Imatinib, so dosage adjustments are necessary.

Treatment for Canine Mast Cell Tumors: Radiation Therapy

Radiation therapy may be performed at facilities equipped with suitable equipment, such as university hospitals. Essentially, like surgery, radiation therapy is a local treatment method. If strong radiation is applied over a wide area, normal tissue will also be damaged due to exposure. Additionally, as there are exposure-related issues, repeated treatment is not feasible.

If you decide to proceed with chemotherapy or radiation therapy, I strongly recommend administering immune support Cordy and liver and kidney care with domestic SPF pig-derived placenta extract powder as measures against side effects.

Treatment for Mast Cell Tumors in Dogs: Others

Other treatments for mast cell tumors include the use of steroids (prednisolone) alone, gastroprotective agents, and antihistamines. Steroids have anti-inflammatory effects, so they are used for palliative purposes to control tumor inflammation.

As gastroprotective agents, cimetidine and ranitidine are used. These are used as supportive therapy for gastrointestinal ulcers caused by histamine secreted by mast cells.

Additionally, antihistamines are used to suppress the paraneoplastic syndrome of mast cell tumors (Darier’s sign: reddening and papules caused by histamine).

However, these treatments do not improve the mast cell tumors themselves; they are used only as symptomatic treatments.

Moreover, the use of krill oil, which is expected to have anti-inflammatory effects, is also recommended.

Prevention Methods for Mast Cell Tumors in Dogs

The exact cause of mast cell tumors is unknown, and therefore, there is no definitive way to prevent them. However, early detection of mast cell tumors can increase the chances of removing them surgically. While not a preventive measure, it is advisable to regularly check your pet’s skin and undergo routine health checkups.

Even if you find a lump or bump, most are benign and not cancerous. There’s no need for excessive worry, but having your pet examined at an animal hospital can alleviate concerns.

Mast cell tumors are more common in older pets, suggesting a link between weakened immunity and an increased incidence of these tumors. Regular immune care can contribute to prevention.

Refer to the following for methods on boosting immunity:

Immune Support for Treating and Preventing Recurrence of Mast Cell Tumors

Surgery to remove the tumor is the primary treatment for mast cell tumors. However, there is a possibility that undetected cancer cells may proliferate again.

We recommend immune support to prevent recurrence after surgery. Cordy can boost immunity without burdening the body.

These photos show the changes after administering Cordy for one and a half months to a dog with a mast cell tumor. Tumor reduction was confirmed after just one and a half months.

Even healthy dogs without mast cell tumors can lower their risk of developing malignant tumors, including mast cell tumors, through lifestyle adjustments and immune support with Cordy.

If your dog has already undergone surgery for a mast cell tumor, Cordy can help prevent recurrence. In cases where tumors have spread locally or metastasized, surgery alone may be insufficient. Immune support in such cases can significantly improve the quality of life (QOL).

Even if conventional medicine fails, it’s still too early to give up.

Cordy is safe for preventive use, with no concerns about the side effects associated with pharmaceutical treatments. Preventing cancer, including mast cell tumors, is the best strategy.

Striving for Extended Life and Overcoming Mast Cell Tumors in Dogs

No one remains unaffected if their beloved dog is diagnosed with a mast cell tumor. However, dwelling on it won’t change the situation. Cancer will inevitably progress over time. If there are benefits, consider surgery or chemotherapy promptly.

Even if standard treatments are deemed ineffective, advanced and alternative therapies may improve the situation. Consider immune support with Cordy and dietary adjustments for nutritional support. These have minimal risk of side effects or loss of strength and can be implemented alongside conventional treatment. Improvements in immunity and well-being are expected with almost no drawbacks.

Reports exist of long-term survival (over 3 years and 7 months) with a diet focused on immune support. There are cases where dogs, whose spleens had ruptured and were rushed to the animal hospital, regained remarkable vigor through natural therapies, including Cordy.

While the extent of response is uncertain, there is a good chance that appetite will improve, and your pet will regain its vitality.

We have helped many dogs with mast cell tumors regain energy and appetite through immune support, allowing them to live life more fully as dogs. Feel free to share your situation with us.

If you have any questions, please contact us.

監修獣医師：林美彩　　所属クリニック：chicoどうぶつ診療所

代替療法と西洋医学、両方の動物病院での勤務経験と多数のコルディの臨床経験をもつ。　モノリス在籍時には、一般的な動物医療（西洋医学）だけでは対応が困難な症例に対して多くの相談を受け、免疫の大切さを痛烈に実感する。
ペットたちの健康維持・改善のためには薬に頼った対処療法だけではなく、「普段の生活環境や食事を見直し、自宅でさまざまなケアを取り入れることで免疫力を維持し、病気にならない体づくりを目指していくことが大切である」という考えを提唱し普及活動に従事している。

所属：

• 獣医保健ソーシャルワーク協会

著書：

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• 獣医師が考案した長生き猫ごはん　安心・簡単・作り置きＯＫ！
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