What is Mast Cell Tumor?

Mast cells are present in most tissues and can form an important part of your cat’s immune system. In the case of a mast cell tumor, the healthy cell begins to mutate and take on an abnormal shape and can grow and reproduce, invading other nearby tissue. Mast cell tumors can be benign (non-cancerous) or malignant (cancerous) and have varying degrees or ratings. Mast cell tumors have a tendency to affect older cats over 10 years of age and are especially prevalent in Siamese cat breeds. Mast cell tumors are also sometimes referred to as mastocytomas.

Mast Cell Tumor Average Cost

From 526 quotes ranging from $3,000 - $8,000

Average Cost

$6,000

Symptoms of Mast Cell Tumor in Cats

Like many tumors, mast cell tumors will begin with raised bumps or growths with an escalation of symptoms depending on the severity of the condition and whether the tumor is cancerous. Symptoms include:

  • Raised growth or bump
  • Loss of hair in area of bump
  • Redness or irritation of bump
  • Can be located on or below the skin
  • Typically located on the trunk or body but can occur in other areas
  • Ulceration may occur if your cat irritates the mass or in severe cases of cancerous tumor
  • If a tumor metastasizes, or spreads, systemic symptoms such as lethargy, general sickness, or loss of appetite may occur.
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Causes of Mast Cell Tumor in Cats

The cause of mast cell tumors, as is the case with most types of tumors and cancers, is unknown. Mast cell tumors form and spread when an unnatural mutation occurs within the healthy mast cell. 

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Diagnosis of Mast Cell Tumor in Cats

Diagnosis of mast cell tumor in your cat will begin with a thorough physical exam. Your vet will examine the suspected tumor and will search your cat for any additional tumors located on other parts of the body. You should provide a thorough medical and physical history of your cat to your veterinarian. It will be especially important to note the approximate date of first appearance of the tumor and the amount of growth since that time. If the tumor has changed in size rapidly, including reduction, this will be especially important for helping your vet determine how aggressive the tumor is.

Your vet will next conduct a biopsy of the tumor. This will often be done using a technique called fine needle aspiration. During this procedure, a needle is inserted into the tumor and is used to withdraw a small number of cells. Your vet will then view those cells under a microscope to determine if there are any cellular changes in appearance, also called differentiation, that could indicate the tumor is cancerous.

If your vet determines the tumor is malignant, he or she may order additional tests to determine whether or not the cancer has spread to any other organs. These tests may include a complete blood panel, fine needle aspiration of the lymph nodes closest to the tumor, and x-rays of the head and chest.

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Treatment of Mast Cell Tumor in Cats

The preferred treatment for mast cell tumors in cats is surgical removal of the tumor. Prior to any surgery, your veterinarian will order a full blood panel in order to ensure there are no additional conditions that would make surgery extra risky for your cat. In preparation of surgery, your cat will be placed under anesthesia. Your veterinarian will attempt to remove as much of the tumor as possible. In the case of cancerous mass cell tumors, your vet will attempt to gain clean margins. This means they may have to remove extra tissue around the edges of the tumor to ensure that all of the cancerous cells have been removed.

In cases which cancer has spread, your veterinarian may opt to treat your cat with chemotherapy. During chemotherapy, strong drugs are administered to your cat. These drugs attack the cancer cells, causing them to shrink or disappear. Chemotherapy is usually administered in several treatments over a number of months and can have serious side effects. These side effects may be lessened by additional medications prescribed by your veterinarian.

In the case of benign mast cell tumors that have become inflamed, your vet may choose an alternative form of treatment involving anti-inflammatory drugs. Anti-inflammatory drugs will reduce the size and slow the spread of the tumor. This will be the treatment of choice for older cats who may be high-risk surgical candidates.

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Recovery of Mast Cell Tumor in Cats

While they may appear frightening, mast cell tumors actually have a good prognosis for recovery. With surgical removal of the tumor, most cats will recover and lead normal healthy lives. As with any surgical procedure, you will need to carefully follow your vet’s post-operative instructions for wound care. You will also need to keep your cat quiet for several days following surgery.

While they can spread, cancerous mast cell tumors do not have a tendency to metastasize or move to other parts of the body. Your cat will need routine follow-up appointments with your veterinarian and careful monitoring on the owner’s part to ensure that tumors do not return or appear in other areas.

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Mast Cell Tumor Average Cost

From 526 quotes ranging from $3,000 - $8,000

Average Cost

$6,000

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Mast Cell Tumor Questions and Advice from Veterinary Professionals

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Jack

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tabby

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11 Years

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Moderate severity

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1 found helpful

pill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filled

Moderate severity

Has Symptoms

Vomiting, Swelling, Itching

My cat Jack has a mast cell tumor on the right side of his neck and it seems to swell every so often and then go down. I’m concerned because the last time it swelled I had to rush him to the emergency vet because he started panting so bad. That night he was diagnosed with diabetes for the first time but they thought it was his mast cell tumor swelling so much that sent him into almost a panic state. I’ve had him for about a year and a half so I don’t know his whole health history. He’s 11 years old and the best kitty ever! His last flare up was in April when we went to the emergency vet. I took him to a new vet after that visit and they put him on insulin twice a day, along with 5mg of Zyrtec. They also said I could use Claritin or Benadryl but I know how Benadryl makes me feel, even the non drowsy, so I choose Zyrtec. His tumor started swelling again this morning and now is very large and hard. Both vets said surgery would be very risky due to its location. Is there anything I can do to help with the swelling now? Of course it always happens over the weekend. Should I increase his dosage of Zyrtec or try Benadryl instead? Thank you!

Aug. 12, 2018

Jack's Owner

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1 Recommendations

Don’t increase the dosage of Zyrtec (cetirizine) as it isn’t approved for use in cats and I have no toxicology data for it apart from standard dosing at 5mg per day; the use of another antihistamine may be useful but since both Zyrtec and Benadryl isn’t approved for use in cats I don’t know of any issues if they are used together. You should keep an eye on Jack for the meantime, but if there are sign of respiratory issues or pain you should go to the emergency clinic to be on the safe side. Regards Dr Callum Turner DVM

Aug. 12, 2018

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dog-name-icon

Tristan

dog-breed-icon

Ocicat

dog-age-icon

15 Years

pill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filled

Moderate severity

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13 found helpful

pill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filled

Moderate severity

Has Symptoms

Hard Nodules On Head And Neck

My fifteen-and-a-half-year-old Ocicat has multiple tumors on his head and neck, and I’m wondering whether it’s worth the risk (and trauma) of surgery to have them removed at this point in his life. They’re probably mast-cell tumors (we’ve removed several of these over the past five years), but these new ones haven’t been tested. He’s running on one kidney, sometimes has a heart arrhythmia, and has some sort of digestive disorder (maybe IBD, but he hasn’t been biopsied) that seems to be well controlled with 5 mg of prednisolone and 5 mg of famotidine every-other day. He’s eating well, isn’t losing weight, and is quite lively. Do you think it’s worth removing the tumors or would you advise just letting them be at this stage of his life?

Aug. 10, 2018

Tristan's Owner


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Dr. Michele K. DVM

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13 Recommendations

That is a very difficult decision to make, sadly. It seems that Tristan is stable and doing well for now, and with so many risk factors for surgery, I would be hesitant to do that surgery. At some point, something ends all of our lives, and it becomes a balance of risk vs benefit. I can't comment on him specifically without examining him, but I would be very cautious having surgery, given what you are describing.

Aug. 10, 2018

Thank you so much for your kind--and swift--response to my question about Tristan! It can be really hard to know when to stop medical interventions on a beloved older cat, so I'm very grateful for your insight and thoughtful advice.

Aug. 10, 2018

Tristan's Owner

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Mast Cell Tumor Average Cost

From 526 quotes ranging from $3,000 - $8,000

Average Cost

$6,000

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