What It Is:
A mast cell tumor is a type of cancer that forms from mast cells, which are a part of the immune system involved in allergic responses and inflammation. In cats, mast cell tumors are one of the most common types of skin tumors, though they can also develop internally, especially in the spleen, intestines, or liver.
There are two main forms of mast cell tumors in cats:
- Cutaneous (skin) mast cell tumors
- Visceral (internal organ) mast cell tumors
The behavior and severity of the tumor depend on its location and whether it has spread.
🐾 Common Symptoms
Cutaneous mast cell tumors:
- Firm, raised lumps on the skin
- Tumors may be hairless, red, or ulcerated
- Most commonly found on the head, neck, or limbs
- May fluctuate in size or shape
- Occasional itching or irritation
Visceral mast cell tumors:
- Vomiting or diarrhea
- Decreased appetite
- Weight loss
- Lethargy
- Abdominal swelling or discomfort
- Pale gums if internal bleeding is present
Some cats with visceral tumors show no signs until the disease is advanced.
🦠 Causes and Risk Factors
The exact cause of mast cell tumors in cats is unknown, but possible contributing factors include:
- Genetics, especially in Siamese cats, who may be predisposed to skin forms
- Chronic inflammation or immune activation
- Age, as tumors are more common in middle aged to older cats, though cutaneous forms can also appear in young cats
Mast cell tumors are not contagious and cannot be passed to other animals.
🔍 Diagnosis
Diagnosis usually begins with a physical exam and evaluation of any lumps. Diagnostic tools may include:
- Fine needle aspirate (FNA) of the mass, examined under a microscope
- Biopsy to confirm diagnosis and assess tumor type
- Bloodwork and urinalysis to evaluate overall health
- Ultrasound or X rays to detect internal tumors or spread
- Spleen or liver evaluation if visceral disease is suspected
The appearance alone cannot determine if a tumor is benign or aggressive — cytology or histopathology is essential.
💊 Treatment
Treatment depends on the location and whether the tumor has spread.
For cutaneous mast cell tumors:
- Surgical removal is the treatment of choice
- Most skin tumors are benign and do not recur if completely removed
- Histopathology helps confirm margins and rule out aggressive types
For visceral mast cell tumors:
- Surgical removal of the spleen or intestinal tumor when possible
- Chemotherapy in cases of metastasis or systemic disease
- Steroids such as prednisolone to help reduce inflammation and tumor burden
- Supportive care, including appetite stimulants, anti nausea medications, and pain control
Cats with internal tumors often need more aggressive treatment and close monitoring.
🩺 Prognosis
Prognosis varies based on tumor type and location:
- Cutaneous tumors have an excellent prognosis when surgically removed
- Visceral tumors, especially those involving the spleen or GI tract, have a more guarded prognosis
- Cats with internal spread or systemic symptoms may have shorter survival, but some respond well to surgery and medication
Early detection and treatment improve outcomes significantly.
💡 Cat Owner Note
Finding a lump on your cat is always alarming, but not every bump is bad. If your vet suspects a mast cell tumor, try not to panic. Many are benign and easily removed. Internal tumors are more serious, but with prompt care and a good treatment plan, your cat still has a fighting chance.
❓ Frequently Asked Questions About Mast Cell Tumors in Cats
Are mast cell tumors in cats cancerous?
Yes. They are considered a form of cancer, but many are benign or low grade, especially those on the skin.
Do mast cell tumors hurt cats?
Not always. Skin tumors are usually painless, but internal tumors can cause discomfort, vomiting, or loss of appetite.
Can mast cell tumors spread in cats?
Some can. High grade tumors or visceral types are more likely to metastasize to other organs.
Should every lump be removed?
Not always, but any lump should be evaluated with a fine needle aspirate to rule out cancer.
What is the survival rate for cats with mast cell tumors?
Cats with cutaneous tumors often live normal lives after removal. Visceral tumor survival depends on location and treatment success.
Can mast cell tumors come back?
If removed completely, recurrence is uncommon. In cases of aggressive or systemic disease, monitoring and follow up care are essential.