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Mast Cell Tumors, The Big “C” Word:
Why It’s Not As Scary As You May Think


So you found a lump and take your pup to the Vet to have it checked out. Hoping it’s nothing, you patiently but anxiously await for your Vet to biopsy and send it into the lab to be tested. A few days later that dreaded phone call comes. The Vet tells you that the lump is a MAST CELL TUMOR, A FORM OF SKIN CANCER, and then gives you a lot of information about MCT and what to do next. Unfortunately, all you have heard is that your beloved dog has THE BIG, SCARY “C” WORD, and the world seems to stop turning. Are they going to die today? Is this the end of the wiggles and the love they bring to your home? Where the heck do you go from here?

Take a deep breath. Let’s start with a simplified way of explaining MCT:

Mast Cell Tumors: What exactly are they?

Mast cells are specialized skin cells that are normal to the body and are randomly distributed throughout the body. They help the body respond to inflammation and allergies by releasing chemicals like histamine and serotonin. When an abnormal formation of mast cells occurs, it is called a Mast Cell tumor. The reason Mast Cell Tumors are considered a form of skin cancer is because of their chemical productions. When so many Mast cells are gathered all in one area (the tumor), the amount of Chemicals they release becomes uncontrollable and toxic; they also begin to maturate and spread. MCT is one of the most common tumors in dogs, which therefore also makes it one of the most treatable due to the amount of research that has been done so far. They typically develop in older dogs, dogs with weakened immune systems, or dogs that have severe allergies. For whatever reason, the boxer breed tends to be more prone to allergies AND cancers and therefore extra prone to MCT.

What do Mast Cell Tumors look like?

MCT’s can form in any shape, size, or location. Helpful and specific, right? Typically it is a raised lump that gradually gets bigger and uglier looking. The lumps can appear just under the skin or can be a growth protruding out of the skin. Most often, the tumors are found on the main body. The second most common location is the legs (hind legs more so than the forelegs) and tail. Lastly, the tumors will form on the head and neck. The most important thing to know is that where there is one, there are probably 2-3 in a different location. One of the major characteristics of MCT’s is that, when they are disturbed by touch, they will actually become red, irritated and swollen due to a histamine reaction from the mast cells. Another tell-tale sign is that the lump will typically change in size, shape and color daily. It will pop up randomly one day and look totally different the next. So as soon as you see a lump, it’s best to get it looked at right away. The further along the MCT progresses, it will actually become an open sore, oozy, and can be painful.

Here are a few different images showing what MCT can look like…


Are Mast Cell Tumors fatal?

If an MCT goes unnoticed and untreated for too long, it definitely can become fatal to your pup. They will gradually spread deeper into the tissue
and eventually into organs, Lymph nodes, and bones. It is one of the slower spreading cancers. When caught early, MCT is usually contained solely within the lump, and once removed all threat of cancer is gone….some good news, right?!

MCT’s can be categorized into 3 Stages.
Stage 1: MCT that has not spread beyond the growth, and upon removal of that lump, the cancer will be gone. This is the most common stage that MCT’s are in when taken to the vet because owners tend to be highly aware of new lumps. So great work for spotting that weird looking growth early!

Stage 2: MCT that has started to spread into the tissue beyond the lump and therefore will require more tissue to be removed to get all of the MCT.

Stage 3: MCT that has spread beyond local tissue and is moving into the organs and other important body structures. Fortunately, most all MCT’s caught by owners are Grade 1, and therefore once they are removed, your dog will be cancer-free. Unfortunately, if the MCT is left untreated for a very long time and it becomes Stage 3, chemotherapy and radiation may be the only possible remedy, and even then it may have spread too much to be beneficial.

What does my MCT prognosis grade really mean?

The prognosis for MCT is divided up into 3 grades.
Grade 1 prognosis means that after the removal of the tumor it is very likely that it will never return and the estimated survival rate is over 90% within a normal lifespan. This is usually the prognosis grade that Stage 1 tumors receive and why it’s important to be vigilante.

Grade 2 prognosis is after the removal of the tumor and its margins a dog will have a survival rate of approximately 4 or more years. Because Grade 2 usually correlates with Stage 2 or Stage 3 MCT, there is a higher risk for recurrence, hence the lower life expectancy. But there are dogs who have live up to their normal life expectancy despite multiple MCT removals, so definitely not something to fret too much about. The more vigilant you can be, the longer your dog may live!

A Grade 3 prognosis is the worst one to have and is held for dogs whose MCT has metastasized into organs, bones, or other vital structures beyond treatment. A dog’s life expectancy with a Grade 3 prognosis is between 6 months to 2 years. Usually due to the spread, a dog’s health is greatly diminished, and they are unable to comfortably make it day-to-day. Comfort care is usually the only option here until it is time to make that hard end-of-life decision.

How do you treat Mast Cell Tumors?

The normal treatment for MCT is a biopsy to confirm the diagnosis and then surgical removal of the lump and surrounding tissues to ensure all possible margins of the tumor are gone. Generally this is a day-surgery, but depending on your pup, it can be an overnight Vet stay. Once the lump has been categorized in its stage further treatment protocols go into effect. It is common for your Vet to prescribe your dog prednisone to help fight further maturation of Mast cells for a few weeks-months. If the MCT has dirty margins (spread too much beyond the surgery site), they may recommend Radiation and chemotherapy to kill the Mast Cells. Fortunately, because most MCT’s caught are Stage 1, the prognosis is really great for your dog. Mast Cell Tumors have a tendency to return in the same place but can also form in a totally new location. Should your dog be diagnosed with MCT, after the lump is removed, a regular monthly self-check at home is very important in order to catch any new growths. Because boxers have a high cancer risk in general, it is very important to regularly check them for lumps even if they have never had MCT, and if you see one, have it tested right away.

Will Mast Cell Tumors come back?

Simply put. Yes. It is very common that once your pup gets their first Mast Cell Tumor, they will likely have another down the road. This means that you need to make a ritual of checking your pet over from head to toe as well as looking and feeling for any lumps or bumps. Since Boxers have a higher cancer risk in general, it is recommended that owners check their pups over once or twice a month.

The Good News?

Yes, Mast Cell Tumors are a form of that big “C” word, and that can be scary, but don’t panic if you get that diagnosis from your vet. There is generally a very good prognosis for MCT and here within the rescue our own volunteers can attest to that from personal experience with their dogs. We have seen MANY, MANY rescue dogs come in with Mast Cells which are removed, and the dogs go on to live happy, healthy, and LONG lives. Boxers are a lumpy bunch! The best advice we can give is that you take your dog to your vet and have that ugly thing removed as soon as you can! Be very vigilant about checking your dog regularly since the earlier MCT is caught the longer life expectancy your dog will have. The bottom line when you see a lump: When it doubt, get it checked out!

****Disclaimer: Although we here at Wigglin’ Home have seen and experienced numerous MCT cases, we are in no way medically certified veterinarians, or have official veterinarian training in order to provide MCT diagnoses or official medical counsel. This article is to provide basic a Mast Cell Tumor summary to our readers in a more simplified manner than reading scientific journal articles and text. Although we try to provide our readers with the best possible information we can, the information used in this article was taken from numerous websites, and WHBR assumes no responsibilities for any inaccuracies or misinformation.


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