Mast Cell Tumor in Dogs: What Is It & What To Do

The majority of this article is written by a certified veterinarian.

First, what is a mast cell? Mast cells are white blood cells found in various body tissues like under the skin, near blood vessels, and in the nerves.

This article will discuss the causes, symptoms, and treatment of the tumors of mast cells — known as mast cell tumors or MCTs.

Mast Cell Tumor in Dogs

Canine mast cell tumors are most commonly found as masses or nodules in the skin. However, they can also affect organs like the spleen, liver, and intestine, or even bone marrow.

Mast cell tumors are very common in dogs and account for about 14-21 percent of all canine skin tumors.

While easily treatable, they are quite invasive, with the ability to metastasize and regrow even after surgical removal.

Though mast cell tumors are typically not painful to the dog, their agitation can cause degranulation, meaning that chemicals can be released into the bloodstream to cause problems elsewhere in the body.

What Causes Mast Cell Tumors in Dogs?

The exact cause for developing mast cell tumors in dogs is unknown to scientists, but several environmental and genetic factors are likely involved.

Some genetic mutations areknown to play a role in the development of MCT, including mutation of the protein KIT, responsible for the replication and division of cells.

These dog breeds are more prone to mast cell tumors: MCT also shows a tendency to affect certain breeds of dogs more. Boxers, Bull Terriers, Boston Terriers, and Labrador Retrievers are especially prone, further pointing towards a genetic cause.

The exact cause for developing mast cell tumors in dogs is unknown to scientists, but several environmental and genetic factors are likely involved.

Some genetic mutations areknown to play a role in the development of MCT, including mutation of the protein KIT, responsible for the replication and division of cells.

These dog breeds are more prone to mast cell tumors:
MCT also shows a tendency to affect certain breeds of dogs more. Boxers, Bull Terriers, Boston Terriers, and Labrador Retrievers are especially prone, further pointing towards a genetic cause.

How to Prevent Dog Mast Cell Tumors?

Unfortunately, since exact causes are unknown to researchers, effectively preventing a mast cell tumor is impossible.

Keeping your dog up-to-date with regular vet appointments makes it easier to identify treatable conditions before they become a serious problem.

Mast Cell Tumor Symptoms / How To Tell

While MCT symptoms vary and many dogs are asymptomatic, some symptoms and signs of mast cell tumor in dogs are as follows.

How to tell if your dog has a mast cell tumor:

• Skin Lump

A sudden lump on your dog’s skin can be a sign of MCT.

What does a mast cell tumor look like in a dog?
These lumps may be found anywhere on the body, and range in appearance from raised lumps to bumps underneath the skin. They may also be red, ulcerated, or swollen.

MCT can appear as a single lump or more than one.

• Decreased Appetite

Mast cell tumors in dogs produce histamine. Histamine is an organic nitrogenous compound involved in the physiological function of the gut, local immune responses, and neurotransmission.

Once released into the bloodstream, histamine affects other tissues and organs, increasing the production of acid by the stomach, amongst other things.

This process eventually leads to stomach and intestinal ulcers, resulting in a decreased appetite.

• Vomiting

Mast cell tumors lead to stomach and intestinal ulcers due to histamine release.

These ulcers then lead to vomiting, which may or may not also contain blood, depending on the position of the ulcers.

The blood can be either bright red or partially digested to resemble coffee ground particles.

If your dog ever vomits blood, even without other symptoms, contact your vet immediately.

• Sluggishness

Stomach ulcers can develop at sites of blood vessels and damage them, resulting in internal bleeding.

When this internal bleeding is slow and long-term, it leads to anemia, which manifests as fatigue and a sluggish activity level.

• Severe Acute Lethargy

The blood loss resulting from some stomach or interstitial ulcers also causes severe acute lethargy.

If your dog displays sudden lethargy and you don’t know why, keep in mind the possibility of a mast cell tumor-induced stomach ulcer, and take your dog to a vet appointment as soon as possible.

• Pale Gums

Anemia due to internal bleeding often leads to pale gums.

In addition, mast cell tumors can cause stomach ulcers, leading to internal bleeding and anemia.

If you notice your dog’s gums looking paler than normal, consider making a veterinary appointment to check it out.

Anemia due to internal bleeding often leads to pale gums.

In addition, mast cell tumors can cause stomach ulcers, leading to internal bleeding and anemia.

If you notice your dog’s gums looking paler than normal, consider making a veterinary appointment to check it out.

• Dark Stool

Rapid bleeding due to stomach ulcers can result in black, tarry stools known as melena.

These dark stools are also a sign of mast cell tumor, as the blood in stool is most likely a result of histamine-induced ulcer formation.

What To Do:
If your dog is pooping blood, it is time to make a vet appointment.

• Anaphylaxis

Canine mast cell tumors release inflammatory mediators that affect the body, causing shock-like symptoms and in rare cases, the life-threatening allergic reaction known as anaphylaxis.

How To Tell:
Swelling around the face, itchy red bumps over the skin and difficulty breathing are common signs of anaphylaxis.

In this case, take your dog to an emergency vet immediately.

What Should I Do If My Dog is Diagnosed With Mast Cell Tumor?

Following all of your vet’s advice can save your dog’s life. Show up to all appointments and follow through with your treatment plan.

If you are worried about paying for a dog mast cell tumor, consider enrolling in pet insurance that covers pre-existing conditions.

When you get a new pet, it’s best practice to enroll in pet insurance right away in case of sudden costly illness such as mast cell tumor.

Dog Mast Cell Tumor Treatment

Once your pet is diagnosed with MCT, your Veterinary oncologist will develop a personal treatment plan based on the prognosis.

Mast cell tumor dog prognosis for low-grade tumors is good, as it is one of the most treatable dog cancers.

Higher-grade tumors are trickier to treat, but the main ways to treat MCT are as follows. How to treat mast cell tumor in a dog:

• Radiation Therapy

A common way to treat cancers and tumors, radiation therapy involves administering small doses of powerful X-rays under anesthesia over the course of four weeks.

It is especially suited for MCT treatment when surgery isn’t viable, but can also be used in conjunction with surgery.

Radiation therapy has localized side effects like hair loss, redness, and ulceration at the treatment site, but doesn’t make your dog systemically ill.

• Chemotherapy

Chemotherapy is cancer and tumor treatment that involves incorporating multiple drugs, including corticosteroids, into a treatment protocol.

Chemotherapy is used to treat tumors that can’t be targeted via surgery or radiation.

This usually includes grade 3 tumors that have already spread or are in areas that can’t be removed. Chemotherapy is also preferred against tumors with a high risk of spread.

• Combination chemotherapy

Combination chemotherapy is different from conventional chemotherapy, as it involves giving multiple chemotherapy drugs simultaneously.

It is more beneficial than simple chemotherapy in a variety of scenarios.

Combination chemotherapy frequently employs the use of the FDA-approved chemotherapeutic drug toceranib, which has been proven to be effective against canine mast cell tumors.

• Surgery

Surgery is the ideal treatment for mast cell tumors limited to a certain region, like lower-grade tumors that show no evidence of spreading.

In these cases, surgery allows for the complete removal of cancerous tissue, eliminating the possibility of spread and providing long-term control.

Unfortunately, surgery is not enough on its own against higher-grade tumors with a high risk of spread. In such cases, a combination of surgery and chemotherapy yields the best results.

• Targeted Therapy

Targeted therapy is a type of cancer therapy focused on blocking the growth and spread of cancer.

This treatment includes drugs specifically designed to target proteins associated with cancer development, in addition to other cancer growth blockers.

Targeted therapy is most often employed for dogs suffering from non-surgical or recurrent mast cell tumors that fail to respond to chemotherapy.

• Palliative Therapy

Palliative therapy is the type of therapy that focuses on reducing the suffering caused by cancer and other such diseases by relieving symptoms.

This includes medication like antihistamines and painkillers that can maintain quality of life, but do not treat or slow disease progression.

Palliative therapy is given alongside other cancer treatments.

• Stereotactic Radiation

Stereotactic radiation is different from traditional radiation therapy in that it can deliver large doses of radiation with sub-millimeter precision. This reduces the number of sessions, further reducing the risks associated with treatment and anesthesia.

SRS/SRT also minimizes collateral damage to nearby tissues and allows for faster recovery with almost no side effects.

This treatment has been shown to be able to treat tumors previously considered untreatable.

Cost to Remove a Dogs Mast Cell Tumor

The cost of mast cell surgery varies based on location, but $500 to $1,000 is a typical starting estimate.

True price:
Costs tend to go up two- to five-fold if the site of surgery is difficult to operate on or internal, as a board-certified surgeon is elected to perform the operation in such cases.

Mast cell surgery is also supplemented with chemotherapy or radiation therapy to get rid of the tumor satisfactorily.

Additionally, the dog’s size, medications used, and the number of rounds further affect the mast cell tumor removal price.

Without pet insurance, the cost of getting rid of mast cell tumor in dogs can be multiple thousands of dollars.

Dog Life Expectancy with Mast Cell Tumor

The median survival time for dogs with MCT treated with surgery alone is 6 months but increases to 12 months when surgery is followed by chemotherapy.

Untreated mast cell tumors dramatically reduce life expectancy to less than a year.

Still, the prognosis for most cases of MCT isn’t quite that bad, provided they receive proper medical attention shortly after diagnosis.

Canine Mast Cell Tumor FAQ

When to Stop Fighting Mast Cell Tumors in Dogs?

Grade III mast cell tumors are usually malignant with a high chance of recurrence after surgery. They are also more likely to metastasize, and dogs with this type of tumor don’t usually survive more than a year.

If your dog is diagnosed with grade III cancer, it might just be best to try to maintain its quality of life as much as possible, or consider euthanasia.

Are Mast Cell Tumors Cancerous?

Yes and no. Mast cell tumors are mostly benign, but can sometimes be cancerous.

They affect dogs’ skin, and are potentially serious as they can be cancerous or give rise to cancer cells later on.

Histiocytoma vs. Mast Cell Tumor?

A histiocytoma is a benign tumor commonly found on a young dog’s head, neck, legs, and feet.

Histiocytoma resembles MCT but affects dogs of all ages, is smaller in size, and is less common.

Histiocytomas regress by themselves after a period of three months. Therefore, any tumor or growth still present after that time duration is unlikely to be a histiocytoma and should be checked by a vet.

Wrapping Up

If your dog was diagnosed with a mast cell tumor, following your vet’s advice and treatment plan could save your dog’s life.

If you suspect a mast cell tumor on your dog based on the symptoms in this article, it’s best to make a vet appointment right away. As they say, “Better safe than sorry.”

Pet insurance can save you hundreds or thousands of dollars when treating illnesses in your dog. It is highly recommended to enroll in pet insurance if you haven’t already done so.