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Mast Cell Tumor Dog Life Expectancy

The life expectancy of a dog with a mast cell tumor depends on the stage and grade of the tumor, the location, treatment options chosen, the particular strain of mast cell tumor and the overall health of the dog.

Most mast cell tumors can be treated with surgical removal without a recurrence.

It’s important to note that very aggressive tumors (considered Grade 3) are also the least common.

The life expectancy of a dog with an aggressive tumor that has spread to other parts of the body (mediatized) is roughly 4 to 6 months.

Assuming the mast cell is in a place where it can be completely removed through surgery (including a wide margin to account for cancer cells not seen) *there is a 90 – 100% chance the tumor will not recur.

[*Source: Long Island Veterinarian Specialists]

Quick Diagnosis is Key to Life Expectancy

Diagnosing mast cell tumors in dogs quickly is essential for a good prognosis. The first step is to obtain a fine-needle aspiration which will help determine whether the mass is cancerous or not.

Fine-needle aspirations and biopsies are two different things.

The fine-needle aspirate involves inserting a needle into the mass and withdrawing cells for examination. A biopsy, however, involves the removal of a small piece of mass for microscopic examination.

The following diagnostic tools may or may not all be necessary. There are a series of steps taken to make an accurate diagnosis.

If the tumor is believe to be benign, testing might stop at the fine-needle aspiration stage. If there is concern that the tumor is cancerous and may have spread, more elaborate testing may be required.

Blood Test

A blood test should be conducted to obtain a complete white blood cell count. A serum chemistry panel and urinalysis help to determine the dog’s overall health condition.

If underlying conditions are diagnosed it can affect the type of treatment options chosen and could affect the dog’s overall life expectancy.


A piece of the tissue is drawn out with a very fine needle and that tissue is examined under a microscope.

The importance of the biopsy is to establish grading of the tumor. Grading of tumors is generally done by a pathologist.

Grade 1

Typically benign or non-cancerous.

Grade 2

There is a possibility that the tumor is cancerous and may invade nearby skin tissue.

Grade 3

Grade III tumors represents a more aggressive tumor likely to have spread to other parts of the body.

Staging is another step that identifies the extent to which the tumor has spread (or not).

Lymph Node Examination

The veterinarian might feel for enlarged lymph nodes close to the mast cell tumor site. 

The examination is painless and can give the doctor a better sense of whether the cancer has spread. If the lymph nodes are enlarged, a local lymph node aspiration may be conducted.

When tumors are found in areas that make it difficult to remove completely through surgery, more tests might be required.

The additional tests help to determine what the treatment options should be.

Abdominal Ultrasound (Sonograph)

Ultrasounds use sound waves to create images of organs within the body. Abdominal ultrasounds are another way to help determine whether cancer has spread to the liver, spleen, and lymph nodes located in the abdomen.


Although radiographs are not entirely helpful in determining the spread of mast cell tumors, they can be useful if there are other underlying conditions present.

Bone Marrow Aspiration

Bone marrow aspiration in dogs involves administering a sedative along with local anesthesia. A needle is then inserted into the bone marrow to remove cells for microscopic examination.

A bone marrow biopsy is more involved and requires general anesthesia. A veterinary surgeon then removes what’s known as a “core sample” of the bone marrow.

Not every dog will require this diagnostic tool.

Mast cell tumor dog life expectancy varies depending on the stage of the cancer.

Mast Cell Tumors Symptoms In Dogs

It’s common for dogs to develop lumps and bumps, especially as they age. Unfortunately, it’s impossible to determine whether a lump is cancerous or not just by looking at it.

Unfortunately, mast cell tumors are complicated and may or may not involve the presence of the following signs:

  • Lumps that randomly increase and/or decrease in size
  • Swollen lymph nodes
  • Loss of appetite (inappetence)
  • Welts on the skin
  • Vomiting
  • Weight Loss
  • Bloody or black stool
  • Pain in the abdomen

Top Treatment of Canine Mast Cell Tumors

The first line of treatment for dogs with mast cell tumors is surgery. The goal is to completely remove the tumor by including a safety margin of 1 inch around the site.

This is performed to ensure that any cancer cells that have migrated into the surrounding skin tissue is removed.

After the initial surgery, the tumor is examined to determine whether it is benign or cancerous and whether it has spread.

If it is cancerous and thought to have spread, further treatment options include:


Radiation therapy helps to permanently destroy any microscopic cancer cells.


Chemotherapy is an option for dogs who have aggressive mast cell tumors thought to have spread to the lymph nodes and organs.

It’s also used for dogs with multiple mast cell tumors occurring at the same time.

Chemotherapy stops cancer cells from dividing and can help reduce the size of a tumor prior to surgery.

Targeted chemotherapy using drugs like Palladia (toceranib) or Kinavet (masitinib) work to slow down the progression of mast cell tumors in dogs.


Prednisone is used in combination with other treatment options and may be useful in shrinking the size of the tumors.

In some cases, it may even create a temporary remission.


Antihistamines help stabilize mast cell tumors in dogs by de-activating excessive histamine release.

Common Side-Effects of Chemotherapy

Dogs typically receive lower doses of chemotherapy than humans. As a result, the side-effects tend to be milder.

Dogs do not lose their fur as a result of chemotherapy, although they may experience appetite loss, vomiting or diarrhea.

Dogs tend to respond very well to chemotherapy with few side-effects. However, if you notice anything unusual or ongoing, be sure to discuss with the veterinarian or veterinarian oncologist.


Remember that most mast cell tumors can be completely removed through surgery and often do not recur or spread.

It’s important, however, to be aware of any new lumps and bumps on your dog. Mast cell tumors are common in dogs over the age of 8, although they have occurred in puppies.

Posting a photograph of the lump on social media is not a substitute for veterinarian care.

Nobody can diagnose a mast cell tumor by appearance alone. Unfortunately, these tumors can look like any number of things. Getting an early diagnosis with treatment offers your dog the best prognosis for long-term life expectancy.

Up next on your reading list:

Is Neosporin Safe to Use on Dogs

Dogs do remarkably well when on chemotherapy


TMS The Mast Cell Disease Society, Inc.

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