[Written by a Veterinarian] Feline Mast Cell Tumors: Symptoms, Treatment, Prognosis, and Daily Care Tips

Have you ever felt anxious after finding a "lump" or "redness" on your cat's skin? One potential cause is feline mast cell tumor. While it often occurs on the skin, it can also develop in internal organs, making early detection the key to successful treatment. In this article, a veterinarian explains the symptoms, treatment, prognosis, and daily care in detail.

What is a feline mast cell tumor?

What kind of tumor is a mast cell tumor?

It is a malignant tumor caused by the neoplastic transformation of mast cells. Originally, mast cells are a type of immune cell involved in allergic reactions and are found in tissues such as the mucous membranes throughout the body.

A mast cell tumor occurs when these cells become malignant and form masses in the skin or internal organs. Because mast cells contain various substances like histamine and heparin, their release can cause swelling, itching, and bleeding. Mast cell tumors are classified into "cutaneous" and "visceral" types.

Differences between the cutaneous and visceral types

The "cutaneous" type appears on the skin; while it is most commonly found on the head or ears, it can occur anywhere on the body. Hair loss and itching are the main symptoms. It is often discovered as a bump that looks like an insect bite. While it can occur as a solitary lesion, it can also present as multiple lesions across the body. The cutaneous form of feline mast cell tumor is typically low-grade and less likely to metastasize.

The "visceral" type occurs inside the body, presenting with symptoms such as loss of appetite and vomiting. Visceral mast cell tumors are prone to metastasis and often carry a poor prognosis. Sometimes, visceral mast cell tumors metastasize to the skin, mimicking the appearance of the cutaneous type. In my own practice, I have encountered one case where a mast cell tumor originating in the spleen metastasized to the skin, resulting in masses appearing all over the body.

Susceptibility and risk factors

The exact causes and risk factors are not clearly understood. There is a tendency for it to occur more frequently in middle-aged to senior cats.

Symptoms of feline mast cell tumors

Symptoms seen on the skin

Cutaneous mast cell tumors are often first discovered as small lumps. Over time, symptoms such as itching and hair loss appear, and redness may develop on the lump and the surrounding skin.

Symptoms when it occurs in internal organs

The visceral type primarily occurs in the spleen and gastrointestinal tract. Because masses form in the organs, symptoms such as vomiting, diarrhea, and loss of appetite appear.

Points to notice before symptoms progress

In the case of the cutaneous type, it appears as an eczema-like lesion resembling an insect bite. If it occurs as a solitary lesion, it may go unnoticed. While a regular insect bite heals quickly, a cutaneous mast cell tumor remains and does not resolve. If your cat seems itchy, observe the area they are scratching closely, and if eczema is present, consult a veterinarian immediately.

Visceral mast cell tumors present with symptoms that could also indicate other diseases. It is important to monitor your cat’s daily food intake and be aware of changes in appetite or the frequency of vomiting.

Treatments and prognosis

Surgical resection

If a cutaneous mast cell tumor is solitary, it can sometimes be cured by widely excising the mass along with the surrounding healthy skin. Since mast cell tumors have extensive infiltration of tumor cells, surgeons typically remove a 2–3 cm margin of healthy skin along with the mass.

For visceral mast cell tumors in the spleen, a splenectomy may be performed. However, since the visceral type may have already metastasized, chemotherapy or other treatments are often used in combination after surgery.

Chemotherapy and radiation therapy

For multiple cutaneous mast cell tumors, those that could not be completely removed by surgery, or visceral mast cell tumors, chemotherapy or steroids may be used. However, the efficacy of chemotherapy in cats has not been fully proven.

Often used in the treatment of mast cell tumors are molecular-targeted drugs, which target specific proteins or enzymes highly expressed in cancer cells. These are characterized by having fewer side effects compared to conventional chemotherapy. They are used for cases of multiple cutaneous mast cell tumors in cats, cases where surgery is difficult, or to suppress metastasis.

Radiation therapy is also used to treat mast cell tumors. It is chosen when the tumor is localized to a specific area. However, it presents challenges, such as the limited number of facilities (like university hospitals) equipped for radiation therapy, the need for general anesthesia, and high costs.

Difference in prognosis based on metastasis

A solitary cutaneous mast cell tumor can be cured by surgical excision, and thus the prognosis is favorable. However, if there are four or more tumors, the survival time is said to be between one and two years. The visceral type has a shorter life expectancy because metastasis occurs early, often leading to death within a year.

Daily care and precautions

Make skin checks a habit

For cutaneous mast cell tumors, it is important to notice skin masses early. Since lumps often form on the head, ears, or neck, you should check these areas regularly.

Care considerations for multi-cat households

Mast cell tumors themselves are not preventable. If there is a lump on the skin, licking can worsen the situation. The tumor cells contain chemical substances like histamine and heparin, which are released upon stimulation. These chemicals can intensify itching or cause the area to bleed easily.

Additionally, some substances can induce gastrointestinal bleeding or trigger vasodilation, which may lower blood pressure and lead to shock. Therefore, try to avoid causing any irritation to the area.

Summary | How to face feline mast cell tumors

Early detection is vital for mast cell tumors. If a cutaneous tumor is treated early, a complete cure is possible. Even with the visceral type, early detection and the prevention of metastasis may help extend the cat's life. Thus, early detection and treatment are necessary.

Because the cutaneous type manifests as visible skin inflammation, you should consult a veterinarian as soon as you notice any skin abnormalities. The visceral type can only be detected via methods like ultrasound. Therefore, you should also seek medical attention if your cat exhibits symptoms such as vomiting, not just skin issues.

Through early detection and treatment, you can help your cat live a better life.