What is Mast Cell Tumor in Cats?

What is Mast Cell Tumor in Cats?

What is it?

Mast cell tumors are a type of skin tumor that is relatively common in cats. They develop from mast cells, a white blood cell type. Mast cell tumors can be benign or malignant and occur anywhere in the body.

How is it Treated?

Mast cell tumors in cats are typically treated through surgical removal of cancer. Chemotherapy and radiation therapy may also be used in more advanced cases. Follow-up monitoring and additional treatment may be necessary to address the cancer’s potential recurrence or spread.

Breed Predispositions

No specific breeds of cats are known to be predisposed to mast cell tumors. However, it is more common in middle-aged to older cats.


Samantha was a proud cat owner who loved her fur baby, Fluffy, more than anything. She made sure to provide Fluffy with the best care possible, ensuring regular check-ups and a healthy diet. One day, while brushing Fluffy, Samantha noticed a small, unusual lump on her side. Alarmed, she immediately scheduled an appointment with the veterinarian. After conducting several tests, the vet delivered the unsettling news: Fluffy had a mast cell tumor. Facing this diagnosis, Samantha felt overwhelmed and unsure of what to expect.

Mast cell tumor in cats is a rare skin cancer affecting cats. This tumor begins in the connective tissue, known as fibrous tissue. It is most common in older cats and Siamese cats. It usually appears as small, red bumps that grow quickly. They can spread to other body parts, including internal organs, bones, lymph nodes, and blood vessels.

MCC occurs when mast cells become malignant and produce large amounts of histamine, causing inflammation and swelling. MCC in cats most commonly occurs in the head, neck, ears, eyes, lips, and paws. Other locations include the tail, perineum, abdomen, thorax, axillae, inguinal region, scrotum, penis, and vulva.

Most cases of MCC are benign tumors, meaning they grow slowly over several years. However, some cases become aggressive and spread quickly. These slow-growing masses often develop spontaneously without apparent cause. However, some cases are associated with systemic diseases such as immune-mediated diseases like allergies, autoimmune disorders, and cancer.

Cats with MCC may be at risk for developing another type of cancer called lymphoma. Lymphoma is a malignant tumor of the immune system that begins in the lymph nodes. Most cases occur in older cats, although younger cats can develop this disease too.

What is a Feline Mast Cell?

Cats have mast cells throughout their bodies. They’re found in the skin, lungs, heart, brain, liver, spleen, kidneys, intestines, stomach, pancreas, bone marrow, lymph nodes, blood vessels, eyes, ears, nose, mouth, testicles, penis, ovaries, uterus, vagina, mammary glands, and tail. About 15% of cats with an enlarged spleen are diagnosed with splenic mast cell tumors.

They play a role in allergic reactions, inflammation, immune response, wound healing, and tissue repair.

There are two types of mast cells: connective tissue mast cells (CTMCs) and mucosal mast cells (MMCs). CTMCs reside in abundant connective tissue, including the skin, lung, gastrointestinal tract, and urinary bladder. MMCs live in the lining of the digestive tract, respiratory system, and genitourinary tract.

What is a Feline Mast Cell?

Both types of mast cell release histamine when activated. Histamine causes itching, swelling, redness, and pain. It also stimulates nearby nerves to send signals to the brain. The brain interprets these messages as signs of danger and sends out adrenaline and cortisol hormones to fight off infection.

When these cells become cancerous, however, they produce too many chemicals called cytokines, which cause inflammation. This inflammation makes fighting infections and tumors harder for the immune system.

What are the Types of Mast Cell Tumors in Felines?

The most common mast cell tumor found in cats is cutaneous mastocytoma. It is the second leading cause of feline cutaneous neoplasms.

Cutaneous mast cell tumors typically grow slowly over many months, and it occurs mainly on the skin surface. Cutaneous Mastocytomas tend to be minor, firm, rubbery nodules that measure less than 2 cm in diameter. These tumors do not spread beyond the skin, and they rarely metastasize.

Another type of mast cell tumor is systemic Mastocytosis. Systemic Mastocytosis affects multiple organs, such as the bone marrow, lymph nodes, spleen, gastrointestinal tract, and liver. Systemic Mastocytosis tumors grow rapidly and are associated with severe clinical signs, such as diarrhea, vomiting, weight loss, abdominal pain, and fever.

The third type of mast cell tumor, urticaria pigmentosa, causes inflammation and swelling of the skin. Urticaria pigmentosa is characterized by redness, itching, and skin flaking.

Other mast cell tumors include mucosal mastocytosis, intestinal mastocytosis, and pulmonary mastocytosis. Mucosal mastocytosis involves the stomach, intestines, or urinary bladder. Intestinal mastocytosis consists of the growth of mast cells within the intestinal wall. Finally, pulmonary mastocytosis requires enlargement of the lung airways due to the infiltration of mast cells.

Causes of Mast Cell Tumor in Cats

The uncontrolled growth of mast cells causes mast cell cancer in cats. It is aggressive cancer, often with several distinct stages which must be identified and treated. In rare cases, the cause of the tumor can be genetic; however, most often, it is caused by environmental triggers such as viruses, chemical toxins or radiation.

Some breeds, such as Ragdolls, Maine Coons, Siamese, and Persians, are known to be predisposed to developing mast cell tumors. Other environmental factors, including exposure to certain chemicals and radiation, may also contribute to the development of these tumors.

Most cats with mast cell cancer have skin mass, but other organs that can also be affected are the lungs, liver, and spleen. Symptoms may include a lump on the skin, typically near the site of infection or trauma; reddening of the skin surface; itching; poor coat health; and difficulty breathing.

facts about mast cell tumor in cats

Symptoms of Mast Cell Tumor in Felines

Mast cell tumors are rare skin cancers that affect both dogs and cats. They are uncommon in cats and rarely metastasize, meaning they don’t spread throughout the body. Most commonly, they develop in the skin and subcutis, although they can also form inside organs such as the stomach and intestines. These tumors grow slowly over many months and cause no pain.

Cats with mast cell cancer often show symptoms similar to those in humans with this disease. These include weight loss, diarrhea, vomiting, lethargy, lack of appetite, fever, and enlarged lymph nodes.

If your cat has mast cell tumors, the number of mast cells in his body will be significantly greater than usual. This means your cat is more likely to develop allergies later in life.

Another vital sign of mast cell cancer is the presence of large numbers of immature white blood cells called neutrophils. Neutrophils are involved in fighting infections. If your cat has too many neutrophils, he may be unable to fight off infection.

Diagnosis of Feline Mast Cell Cancer

Diagnosis of Feline Mast Cell Cancer

Vets use several methods to determine whether a cat has cancer. The most common method involves taking biopsies (samples) of suspicious areas of skin. This process is called cytology.

Cytology is performed by inserting a needle through the skin and collecting cells from the examined area. Vets may also take samples of fluid from cysts or masses. They may also perform blood tests to detect certain types of cancers.

The vet recommends further testing if a mass is found during a physical exam. Some vets may refer the patient to a specialist specializing in veterinary medicine.

When diagnosing a tumor, the vet must consider many factors. These include the location of cancer, its appearance, and any symptoms the pet is experiencing. Some pets experience no signs at all. Other pets may show only minor characteristics, such as lethargy, weight loss, vomiting, diarrhea, coughing, sneezing, or excessive scratching.

Other pets may exhibit more severe signs, including difficulty breathing, lack of appetite, fever, bleeding from the nose or mouth, swollen lymph nodes, pain, stiffness, seizures, paralysis, coma, or death.

The vet may order additional diagnostic tests to help identify possible causes of these symptoms. These tests may include X-rays, ultrasound scans, CT scans, MRI scans, bone marrow aspirations, blood work, or endoscopy.

Once the diagnosis is made, the vet will discuss treatment options with the owner. Treatment depends on the type of cancer and the stage of development.

Treatment for Mast Cell Tumors in Felines

Treatment may involve surgery, chemotherapy, radiation therapy, immunotherapy, hormonal treatments, or combinations of these approaches.


Surgical removal often treats mast cell tumors because it obliterates cancer. It may be done using local anesthesia, general anesthesia, or sedation. In some cases, it may require opening up the chest cavity. However, it may only be necessary for some patients. Surgery is usually recommended when the tumor is large, or there is evidence of metastasis (spread).

Surgery is usually recommended when tumors are large, invasive, or recurrent. Surgery may be combined with radiation therapy, chemotherapy, or both.


Mast cell tumors are mainly treated through chemotherapy because it destroys cancer cells. The chemotherapy drugs work by damaging DNA inside the cancerous cells. This makes them unable to reproduce and grow.

Two chemotherapy drugs are available for treating mast cell tumors in cats: alkylating agents and antimetabolites. Alkylating agents work by damaging DNA and preventing cells from dividing. Antimetabolites prevent cells from making proteins necessary for growth. Both drugs cause side effects, including vomiting, diarrhea, hair loss, weight loss, and decreased appetite. The length of therapy varies depending on the type of drug used and whether the tumor is localized or metastasized.

Radiation Therapy

Radiation therapy can be necessary to control cancer. Radiation therapy uses high-energy x-rays to kill tumor cells. The goal is to destroy enough cells to shrink the tumor.

There are several different types of radiation used to treat mast cell tumors. Each type works differently, and each has its benefits and drawbacks.

One standard treatment option is called fractionated external beam radiotherapy. This involves placing tiny radioactive pellets inside the cat’s body. These pellets emit radiation over weeks. Fractionated external beam radiotherapy is typically given once per week for 4–6 treatments.

Another standard treatment option is called brachytherapy. Brachytherapy involves inserting tiny tubes containing radioactive material directly into the tumor site. This technique delivers radiation continuously over a long period.

Brachytherapy is usually done only when there are multiple tumors throughout the body. It’s not recommended for treating just one tumor because it doesn’t work well at destroying microscopic metastases.

Fractionated external beam radiography is usually preferred for cats, not candidates for brachytherapy. However, some cats prefer brachytherapy because it allows them to remain active during treatment. Both techniques are effective at shrinking tumors and controlling symptoms. But they differ in their side effects.

Side effects include hair loss, weight gain, diarrhea, vomiting, fatigue, and mouth ulcers. Some cats experience these side effects for months after treatment. Other possible side effects include infection, kidney damage, and bone marrow suppression.

Some cats develop a condition called radiation dermatitis. This occurs when the skin becomes irritated by the radiation. It causes redness, itching, swelling, and pain. Radiation dermatitis usually resolves within 2–3 days. But it can last longer than one month.


Immunotherapy involves injecting a cat with substances called cytokines. These substances stimulate the immune system to attack cancer cells. The goal is to destroy any remaining cancer cells.

Two types of immunotherapy are used to treat mast cell tumors in cats. One type uses interferon alpha, a naturally occurring substance the body produces. Another type uses recombinant human interleukin 2 (IL2).

Both treatments work well, but IL2 is considered safer because it doesn’t cause side effects associated with interferon-alpha. However, no long-term studies are available to compare these two treatments’ effectiveness.

Hormonal Treatment

Hormone therapy is used to treat MCTs when they become cancerous. The goal of hormone treatment is to shrink the tumor and prevent metastasis.

There are two types of hormonal treatments available: topical and systemic. Topical hormones work directly on the affected area, whereas systemic hormones influence the entire body. Both types of hormone therapy require daily administration of medication for several weeks.

Topical hormones include corticosteroids, imiquimod, and 5-fluorouracil cream. Corticosteroids are anti-inflammatory medications that reduce itching and inflammation associated with MCTs. Imiquimod is a synthetic drug that stimulates immune cells to attack and destroy MCTs. This treatment works well for small lesions but not large ones.5-Fluorouracil cream is another standard topical treatment option. It contains a chemical called fluorouracil, which kills rapidly growing cells.

Systemic hormones include vinblastine, cyclophosphamide, and chlorambucil. These drugs target rapidly dividing cells throughout the body, including those that cause MCTs. In addition, systemic hormones are often combined with radiation therapy to kill the remaining cancer cells.

Depending on the type of cancer, some pets may require multiple rounds of treatment over months or years. After treatment, the vet will monitor the pet’s progress. They may suggest regular visits to prevent the recurrence of the disease.

Cats diagnosed with mast cell tumors typically live longer than those diagnosed with other forms of cancer. However, there is still a risk of relapse.

Prevention for Feline Mast Cell Tumors

Mast cells are part of our immune system. They produce histamine, an inflammatory chemical that helps us fight off infections. However, too much histamine production can cause problems.

They develop most often in older cats, especially those that are neutered. This is because neutering decreases testosterone levels, which may increase mast cell tumor growth.

Cats with mast cell tumors usually don’t seem sick until they age. This makes prevention difficult.

However, there are things you can do to decrease your cat’s chances of developing a mast cell tumor.

  • Make Sure He Has Enough Exercise

Exercise is essential for keeping your cat fit and healthy. Cats that exercise regularly tend to live longer than sedentary cats.

Ensure your cat has plenty of opportunities to run, jump, climb, play, and explore. If he doesn’t have access to safe places, give him his space away from traffic areas.

  • Give Him Safe Places to Hide

Some cats find comfort in hiding. If your cat likes to hide under furniture or behind curtains, provide him with a safe place to retreat whenever he feels stressed or anxious.

  • Don’t Overfeed Him

Overfeeding can contribute to obesity, leading to health issues such as diabetes and kidney failure. So be careful not to overfeed your cat.

Keep feeding amounts within recommended guidelines.

  • Watch Out For Signs Of Illness

Watching for signs of illness in your cat is another way to protect against mast cell tumors.

Look for changes in behavior, appetite, activity level, and sleep patterns.

If any of these symptoms occur, contact your veterinarian right away.

  • Get Regular Checkups

Regular veterinary visits are vital for maintaining overall health. Mast cell tumors are one of several types of cancers that can affect cats.

Have your vet perform regular exams and tests to detect potential problems early.

  • Talk To Your Vet About Preventive Medications

There are medications available to treat mast cell tumors. These drugs can slow down the rate at which the tumors grow.

Talk to your vet about whether preventive medication would benefit your cat.

  • Monitor His Health Carefully

Monitor your cat’s health care. If you notice anything unusual, contact your vet immediately.

  • Avoid Exposure To Certain Chemicals

Certain chemicals found in household products can trigger mast cell tumors.

Be aware of what you’re using and where you’re placing it.

Avoid cleaning products containing ammonia, bleach, and paint thinner.

  • Reduce Stress Levels

Stress can increase your cat’s likelihood of developing mast cell tumors.

Reduce stress in your life by taking care of yourself and your relationships.

Take breaks from worrying and focus on relaxing instead.

Frequently Asked Questions

The average lifespan of a cat with mastocytoma is around seven years. Some cats live longer than ten years. But some die from complications before reaching ten years old. Several factors affect how long your cat lives with mastocytoma.

One factor is if you take your pet to a veterinarian regularly. If you do so, your vet will know what treatments work best for your cat’s condition. Another factor is whether your cat gets any infections. Infections can make your cat sick and shorten its life. You should keep track of any signs of illness and call your vet immediately if you notice anything unusual.

Mast cell tumors can vary in their aggressiveness and response to treatment. However, some cats may survive mast cell tumors if treated early on and have a good prognosis.

Cats who develop mast cell tumors usually live only one year after diagnosis. However, some cats live longer than ten years. In addition, cats with mast cell tumors can live up to 20 years in rare cases.

No. Mast cell tumors can be benign or cancerous depending on the grade and location of the tumor. Most mast cell tumors are benign, but a small percentage can become cancerous.

The speed at which mast cell tumors spread depends on many factors, including how aggressive the cancer is, where it starts growing, what kind of tissue it increases in, whether any nearby lymph nodes are involved, and if the patient has had radiation therapy before.

The degree of metastasis depends on several factors, including the grade and stage of the tumor, as well as the size and location. The grade quality is based on how abnormal the cancer cells appear under a microscope; high-grade MCTs are typically more aggressive and are more likely to spread to other organs. Stage refers to how far beyond the original site of formation cancer has grown. For example, grade 3 MCTs tend to spread most quickly.

A mast cell tumor looks like a dark red mass under the skin. It usually grows slowly and painlessly. The most common sites include the ears, nose, eyelids, lips, paws, tail, chest, abdomen, back, head, neck, and genitals.

It is believed that mast cell tumors (MCTs) may be more common in cats with liver disease. Cats with MCTs are often sicker than other cats and may have jaundice or ascites. They also tend to die sooner than cats without MCTs. It is not clear why this might be, but one possibility is that a cat’s liver can’t metabolize anticancer drugs or a cat’s kidney or other organs are affected by the same disease process.

Your cat may have a mast cell tumor in their intestine. This type of tumor can be deadly and requires immediate treatment if detected early on. However, surgery may also be necessary to remove cancer if cancer grows or spreads.

Mast cell tumors in cats do not always need to be removed, but a veterinarian should evaluate them. Removal can depend on the size and location of the cancer.

They can develop anywhere on the body but are more common in older cats. A mast cell tumor may look like an accumulation of white or yellow pus near the ear canal or within the inner ear. If the cancer is large, it may block hearing or vision in one or both ears.

If your cat has exhibited the following signs or symptoms, it may be at risk: licking and biting its paws excessively; hair loss on its back; frequent urination or diarrhea; weight gain or loss without reason. A veterinary visit should be considered in cases where these symptoms persist for more than two weeks. Mast cell tumors can initially seem like benign skin conditions, but if left untreated, they can spread to other parts of the body and cause serious health problems.

Cutaneous mast cell tumors (CMCTs) are benign masses found on the skin, often in cats. CMCTs are most commonly seen in middle-aged to elderly cats but can also occur in younger cats. The tissues that make up a CMCT vary from the nodule to mass and may be red, purple, or white with varying amounts of scaly surface debris. There is a chance that a CMTC will grow slowly or not at all and eventually disappear on its own; however, if it is deemed cancerous by your vet, surgery may be required to remove it.

The prognosis of cats with mast cell tumors is typically good. Mast cell tumors can rarely spread to other body parts, and most cats will survive without significant health problems. However, some mast cells may grow large enough to cause serious health concerns, so it is essential to seek veterinary care if your cat has a suspected tumor.

Disclaimer: The information provided on this veterinary website is intended for general educational purposes only and should not be considered as a substitute for professional veterinary advice, diagnosis, or treatment. Always consult a licensed veterinarian for any concerns or questions regarding the health and well-being of your pet. This website does not claim to cover every possible situation or provide exhaustive knowledge on the subjects presented. The owners and contributors of this website are not responsible for any harm or loss that may result from the use or misuse of the information provided herein.

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