Web Only Article February 1, 2019

Mast Cell Tumors in Dogs: Is It Always Cancer?

Mast cell tumors are common in dogs. Early detection and staging is critical to diagnoses and successful treatment.

Mast cell tumors (MCTs) are one of the most frequent skin cancers seen in dogs. Mast cell tumors are the reason why careful monitoring of any skin growths is essential for maintaining a healthy canine. Any new masses on the skin should be evaluated by your veterinarian. In regards to MCTs, there are several predisposed breeds including Boxers, American Staffordshire terriers, and pit bulls.

Mast cells are important in the immune system, particularly in allergic reactions. They are found predominantly in the skin, but they are also found in lower numbers throughout the internal organs. Rarely are they found in the bloodstream. These cells are filled with substances such as histamine and heparin. During an allergic reaction, they degranulate - meaning they empty their contents onto or in the area of the offending allergen. The effect of mast cells can be seen when a patient develops hives and welts, as well as itching and redness.

dog veterinary treatment

iStock/ Getty Images Plus/ Chalabala

As with any cell in the body, mast cells can develop cancer. The word cancer merely means the uncontrolled proliferation of cells. It can be divided into 2 broad categories - malignant and benign. Malignant cancers can be locally invasive and damaging, spread to other organ systems like the lungs, or both. Benign tumors do not spread to other organs and are cured by removal.

tumor on a dog

iStock/ Getty Images Plus/ Elen11

The symptoms of a MCT on dogs begin with a skin mass, most of the time (in rare circumstances, they can start in the internal organs, but this is more common in cats). They can be as small as a pea or as large as a softball. One important aspect is that they tend to wax and wane. They can start as small and suddenly become large, red, and irritated or weepy. This is a sign of degranulation, meaning the tumor has become irritated and released the nasty substances within it. The hallmark of a mast cell tumor is a tumor that grows and shrinks periodically.

If you note a skin mass on your dog, it should be checked by your veterinarian. As with any veterinary visit, your dog should have a nose-to-tail examination including weight and vitals, followed by a detailed history. Your veterinarian will ask how the mass has behaved, how long it has been present, and if it has changed significantly. They may also measure it with calipers.

After a history and physical exam, your veterinarian will focus on the mass with gentle palpation. It is likely they will recommend a fine needle aspirate. This involves taking a very small needle and obtaining a sample of cells from the tumor.† Another option is just having the entire mass removed and submitted for testing (excisional biopsy).

If your veterinarian is suspicious of a mast cell tumor and wants to sample it, they may recommend pre-medicating with Benadryl, an antihistamine. As we discussed above, one of the substances found in mast cells is histamine. Giving Benadryl may help prevent the tumor from degranulating during sampling. Sudden degranulation can cause a systemic reaction (anaphylaxis) and can be very serious or even life-threatening. Your veterinarian will handle any suspected MCTs gently, as a result.

Diagnosis is generally by a veterinary pathologist. MCTs are graded on two different scales - the older Patnaik scale (giving a number I through III with I being the least malignant), and the newer Kiupel system that simply evaluates high grade versus low grade.

dog tumor

iStock/ Getty Images Plus/ cynoclub

If your dog is diagnosed with a mast cell tumor, your veterinarian will recommend staging as the next step. This means determining if the cancer has spread by conducting bloodwork, urinalysis, chest xrays, and abdominal ultrasound. Once staging is completed, a clearer picture of prognosis can be seen.

Treatment of mast cell tumors in dogs involves initial surgical removal followed by evaluating whether the whole tumor was removed. If it wasn’t (called “dirty margins”), a second surgery may be needed. Radiation is also an option when the entire tumor wasn’t removed. It may seem “simple” to remove a whole tumor, but sometimes the cancer cells have infiltrated the surrounding tissue on a microscopic level. For low grade (Kiupel system) or grade I-II (Patnaik system), usually removal is sufficient if the margins are clear. Even with removal, a dog will be at higher risk for developing MCTs again.

With high grade/grade III tumors, following surgery, oncologists recommend chemotherapy. This is usually administered by a veterinary oncologist. If chemotherapy is not pursued, a dog with high grade MCT will likely stay on Benadryl and steroids to suppress the MCT until symptoms become too severe. As the disease progresses, the mast cell tumor will spread to distant sites like the liver, spleen, and lungs. Symptoms will correlate with the system that is affected.

A mast cell tumor is not the end of the world, but they can be very serious. It is important to notify your veterinarian when you find any skin masses so that they can be promptly evaluated. Early detection and treatment are critical to a successful outcome.

Comments (17)

I have some curcumin at home. What would be the recommended daily amount for a 100# dog?

Tia. Blessings and prayers for all our dogs, us, and the medical teams.

Posted by: Never_Alone | March 10, 2019 7:41 PM    Report this comment

I have some curcumin at home. What would be the recommended daily amount for a 100# dog?

Tia. Blessings and prayers for all our dogs, us, and the medical teams.

Posted by: Never_Alone | March 10, 2019 7:40 PM    Report this comment

For Susi: You're welcome, and I hope that it helps your fur baby.

For BentleyBoo: I followed the dosage instructions on the product I use (Mercola Curcumin for pets). Dosage is determined by weight.

Posted by: allysmom | March 10, 2019 11:19 AM    Report this comment

I lost a dog to MCT. He had a pea size lump on his leg as a pup. It slowly grew to marble size and super ball size and yet my vet would not remove it, saying it was a fatty tumor. One day his leg blew up like a baseball bat size. Too late. Donít assume all growths are fatty benign tumors. If itís a growth, it does not belong. Get an aspiration of cells. Several years later my new dog showed a lump on his leg at age 2 1/2. Again, my vet said it was nothing. I had him remove it and biopsy it. It was hemangiopericytoma.He went through treatment for it and lived to age 14.My current vet did not check my dogs anal glands on visit and missed an anal sac tumor. When we discovered it by accident, he had second stage metastasis in his abdomal lymph node. Both were operated on, There is no cure for this cancer but his life expectancy could have been higher with an early detection. My dog has now survived 17 months on treatment but we will lose him. My point. Be proactive in the say so of your dogs care. Insist...You are paying for it. If not, find a vet who will do it. Vets are not always right, just like human doctors. I love myvets but they are human and make mistakes.

Posted by: Love My Rescues | March 10, 2019 10:42 AM    Report this comment

To allysmom: Thanks for the curcumin recommendation. Iíve purchased from Mercola before but am presently using a different curcumin. I just sent in an order to Mercola so weíll see how well it works for my 12-year-old girl.

Posted by: Susi | March 4, 2019 4:17 PM    Report this comment

For Maggie May: The product I use is sold by Mercola. It's called Curcumin For Pets. I'm unable to post a link here, but if you search under Mercola it will be easy to find. Other owners used products formulated for bone and joint pain that contain curcumin, so you may get good results with those.
The Mercola product is a fine powder that I add to her food twice a day. The dosage is determined by the dogs weight, and I just follow the instructions on the jar. My dog is entirely raw fed, and the curcumin mixes easily with a little raw ground meat. But if that doesn't work for you it could probably be added to any soft food your pet enjoys, like yogurt, yam, or peanut butter. Good luck.

Posted by: allysmom | March 3, 2019 8:23 PM    Report this comment

P.S. I'm not neurotic actually, just pro active! My best friend and business partner must live a very long life

Posted by: loveonaleash | March 3, 2019 6:31 PM    Report this comment

My Ozzie had small bumps on his tummy and chest, some got slightly bigger in a month or so...but being a neurotic dog Mom I had my vet look at every one(cytology in office) .yup, mst which I had no knowledge about. I read every article and journal I could and elected to have them all removed surgically ,and some sent out to a lab to be biopsied(expensive!) Results were grade 1 and my wonderful vet got clear margins. Ozzie is probably 12, as they fibbed about his age at the humane society when he adopted me 4 yrs ago.
So appreciate reading others experiences.
Thank you. Puppy hugs

Posted by: loveonaleash | March 3, 2019 6:27 PM    Report this comment

What is the dose of curcumin you give your dog? We have a Jack Russell Terrier and would love to give him curcumin. Thanks

Posted by: BentleyBoo | March 3, 2019 6:24 PM    Report this comment

In 1987 I moved with my dog to Ft Collins Co so he could be regularly seen at CSU Vet Teaching Hospital. At that time they were highly regarded in oncology. At 6 years old he was diagnosed with Mast Cell cancer and given 6 months to survive. I mapped his body and did weekly searches for lumps and bumps which resulted in 22 tumor removals over several years. He was a Lab Airdale mix and tough as nails. I realize not all dogs can handle such events. My sweet boy died at 17. I learned keeping diligent notes (multiple notebooks) not relying on any one veterinarian or any one person while keeping myself fully in front of the situation was key to success. Like anthing, you're taken more seriously the more educated you are and the more productive effort you provide. I've since lost 5 more dogs and my mother to cancer. There are no rules for its cruelty.

Posted by: Dudley's mom | March 3, 2019 5:47 AM    Report this comment

In 1987 I moved with my dog to Ft Collins Co so he could be regularly seen at CSU Vet Teaching Hospital. At that time they were highly regarded in oncology. At 6 years old he was diagnosed with Mast Cell cancer and given 6 months to survive. I mapped his body and did weekly searches for lumps and bumps which resulted in 22 tumor removals over several years. He was a Lab Airdale mix and tough as nails. I realize not all dogs can handle such events. My sweet boy died at 17. I learned keeping diligent notes (multiple notebooks) not relying on any one veterinarian or any one person while keeping myself fully in front of the situation was key to success. Like anthing, you're taken more seriously the more educated you are and the more productive effort you provide. I've since lost 5 more dogs and my mother to cancer. There are no rules for its cruelty.

Posted by: Dudley's mom | March 3, 2019 5:46 AM    Report this comment

Would ''allysmom'' kindly explain HOW exactly is curcumin administered?
Thank you.

Posted by: Maggie May | March 3, 2019 5:42 AM    Report this comment

My 12 year old dog developed an MCT on her foot. It was biopsied and diagnosed as an MCT. It was removed surgically and took considerable time to heal and treat the wound but it never came back and she was fine. I found the vets bandaged her foot too tightly and she chewed it off about four times until I undertook to bandage myself. She never chewed off another bandage. BTW, I found one of the best ways to keep it fairly clean and dry was to put a baby sock over the bandage and tape it. There was never a problem.

Posted by: Holly 1 | March 2, 2019 2:15 PM    Report this comment

Forgot to add that post surgery she did not require any radiation, chemotherapy or any medication other than some antibiotics and pain meds. Get pet health insurance everybody! Otherwise you might not have the luxury of making choices with the treatment of your beloved friend.

Posted by: kimfatty | March 2, 2019 12:13 PM    Report this comment

My eldest dog had a mast cell tumor on her foot which was uncomfortable for her, we had it removed. A few years later during a routine exam my Florida vet found something tiny which he suspected might be mast cell tumor, he ran some tests and advised that we have our regular vet look at it when we returned to New York the following week. We did, and he sent us to an oncologist. It turned out to be mast cell tumor, when we brought her in for surgery they found that her entire mammary chain had cancerous tumors plus there was an invasive cancerous tumor in her thigh which required removal which required removal of a significant piece of her thigh muscle. It took a while for her to walk normally again, but she is now 16 and walking/behaving like a(n old) trooper. It is really important that your vet do a thorough exam and you point out all the lumps that you find to your vet for further examination. Otherwise we would have lost our old girl at 12.

Posted by: kimfatty | March 2, 2019 12:09 PM    Report this comment

Why put an animal through multiple surgeries, chemo, and radiation? Curcumin has been used to completely remove these tumors. My dog had her MCT surgically removed, and before her incision healed another tumor came up beside it. She suffered so much through that surgery that the prospect of subjecting her to another procedure broke my heart. I looked at all of the research and found that curcumin was effectively treating these tumors in dogs. I immediately started her on curcumin and within 2 weeks her tumor started to get smaller. Today it's completely gone, and she hasn't developed any new tumors. It not only dissolves MCTs, but is very effective in controlling the pain of arthritis and other bone and joint disorders. My dog also had a bad disc that caused her so much pain she started to limp. After putting her on curcumin she is pain and limp free. Curcumin is non-toxic, inexpensive, readily available, and needs no prescription. Why not try this before subjecting an animal to surgery, chemo, and radiation, and their owners to huge veterinary bills?

Posted by: allysmom | March 2, 2019 11:35 AM    Report this comment

Early detection is key. Take the time to look your dog over from head to toe regularly. My dogs have had MCTs but fortunately because we caught them early, they were very low grade and had not spread. And looking your pet over is a good idea anyway. You never know what you might find and almost any problem is better addressed early.

Posted by: puppypig | March 2, 2019 11:17 AM    Report this comment

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