FR
ENWhat is a mast cell tumor?
Mast cells are white blood cells specialized in immune and inflammatory responses. When they proliferate abnormally and uncontrollably, they form a mast cell tumor (MCT). These tumors contain granules packed with histamine and other potent chemicals: their release can trigger local or systemic reactions that are sometimes severe.
Mast cells and granules
Each tumor mast cell holds histamine granules. When released (through manipulation of the tumor, stress, or spontaneously), they cause local swelling, redness, and can trigger gastric ulcers or an anaphylactic reaction.
Unpredictable behavior
Some cutaneous MCTs remain stable for months; others grow rapidly or spread to lymph nodes, the liver, or spleen. Histological grading guides prognosis and the treatment plan.
Siamese predisposition
Siamese cats are overrepresented in MCT cases, particularly in multiple forms. A genetic mutation has been identified as a risk factor. Multiple MCTs in Siamese cats often behave in a more indolent fashion.
Malignant but often manageable
Although technically malignant, approximately 90% of feline cutaneous MCTs behave clinically close to benign. This contrasts with dogs, where MCTs are more often aggressive. Early, tailored treatment gives good results.
Frequently handling a suspicious mass can release histamine and cause sudden local swelling (Darier's sign). Avoid repeatedly palpating the mass and report any rapid change to your veterinarian.
Skin form vs visceral form
- Mass on or under the skin, often on the head or neck
- Variable appearance: firm nodule, erythematous lesion, sometimes ulcerated
- 90% considered low-grade or benign behavior
- Surgery is often curative if removal is complete
- Generally favorable prognosis
- Involvement of the spleen, liver, intestine, or bone marrow
- Systemic symptoms: vomiting, weight loss, depression
- Gastric ulcers common (histamine excess)
- More guarded prognosis, especially with severe signs
- Splenectomy can significantly improve quality of life
The same tumor can evolve from one form to the other. Any new lump on your cat deserves a veterinary evaluation, even if it appears small and painless.
Signs and symptoms
Signs vary considerably depending on the location (cutaneous or visceral) and disease stage. This three-level progression helps you assess the urgency of the situation.
Early stage
- •Decreased energy, less interest in play
- •Mild to moderate weight loss
- •Anorexia or reduced appetite
- •Occasional vomiting or nausea
- •Skin mass found by touch
Intermediate stage
- •Repeated vomiting, diarrhea
- •Abdominal pain (hunched posture)
- •Unkempt coat, neglected grooming
- •Withdrawn behavior, isolation
- •Mild breathing difficulties
Advanced stage
- •Red, swollen, or ulcerated skin masses
- •Abnormal bleeding, slow wound healing
- •Sudden collapse or prostration
- •Pale or yellow gums (jaundice)
- •Seizures (rare, severe systemic involvement)
When to seek immediate care?
Some signs indicate a medical emergency. Go to a veterinary clinic immediately if you observe:
- Marked breathing difficulty: labored breathing, open-mouth breathing, panting
- Blue or white gums or tongue (shock, severe anemia)
- Sudden collapse or inability to walk
- Uncontrollable vomiting or diarrhea with visible blood
- Sudden rapid swelling around a skin mass (massive histamine release)
- Intense pain: vocalizing, refusing to be touched, frozen posture
How is the diagnosis made?
Diagnosing an MCT is often simpler than for other cancers, thanks to cytology, which can confirm the mast cell nature of cells in minutes. Further workup establishes the grade and extent of disease.
Physical exam and mass evaluation
The veterinarian assesses the appearance, size, location, and character of the mass, along with regional lymph nodes. Systemic symptoms point toward visceral involvement.
Fine needle aspiration (cytology)
A few cells are collected with a syringe and examined under the microscope. This quick technique often confirms MCT diagnosis through the characteristic granules visible on staining.
Biopsy and histological grading
Surgical excision or a biopsy provides a definitive diagnosis and assigns a grade (low, intermediate, high). Grade is the most reliable indicator of tumor aggressiveness and guides treatment.
Staging workup
Abdominal ultrasound (spleen, liver, lymph nodes), chest X-rays, complete blood work, and sometimes bone marrow aspiration to assess disease extent before deciding on treatment.
Treatment options
Treatment depends on grade, location, extent of disease, and the cat's general health. A combination of approaches is often optimal.
- Wide excision: first option for cutaneous MCTs. Complete removal with adequate margins can be curative for low-grade forms.
- Splenectomy: removal of the spleen in cases of splenic involvement; often notably improves quality of life and extends survival even in advanced disease.
- Clean margins: histological margin analysis confirms whether the tumor has been completely removed.
- Lomustine (CCNU): chemotherapy used for high-grade or metastatic MCTs.
- Tyrosine kinase inhibitors: targeted molecules (imatinib, toceranib) showing promising results in MCTs with c-Kit mutation.
- Radiation therapy: considered for locally advanced MCTs or where surgical margins are insufficient.
- Corticosteroids: prednisone to reduce inflammation and tumor mast cell degranulation.
- Antihistamines: diphenhydramine or others, to limit the effects of histamine release.
- Gastroprotectants: famotidine or omeprazole to prevent gastric ulcers caused by histamine excess.
What to expect?
Prognosis depends primarily on the form (cutaneous or visceral) and the tumor grade. Early detection and appropriate treatment make a major difference.
Regularly petting your cat during cuddle time lets you detect any new lump quickly. The earlier the diagnosis, the more treatment options are available and effective.
Home management and comfort
To implement
- Administer all medications at the prescribed doses and times
- Check your cat's skin weekly: new masses, size or appearance changes in existing masses
- Provide food and water in easily accessible spots (elevated if needed)
- Offer warm, quiet, comfortable resting areas
- Use ramps or steps for access to usual surfaces if your cat is weakened
- Monitor appetite, weight, stools, urination, and breathing daily
- Reduce stress sources (noise, conflicts with other animals)
- Consult promptly if new symptoms appear or general condition worsens
- Schedule follow-up oncology visits at the recommended frequency
To avoid
- Repeatedly handling or massaging a suspicious mass (risk of degranulation and histamine release)
- Stopping a medical treatment (corticosteroids, antihistamines) without veterinary guidance
- Giving human anti-inflammatories (aspirin, ibuprofen): dangerous for cats
- Delaying consultation if a new mass appears or an existing one changes rapidly
Preventive care
- Keep vaccinations up to date
- Regular dewormers and antiparasitic treatments
- Annual health checks (twice yearly for cats over 10)
Frequently asked questions
How can I tell an MCT from a simple cyst or wart?
My Siamese cat has several small bumps on its skin. Is that serious?
Why is my vet prescribing antacids for a tumor?
Is surgery always necessary?
Are there useful natural or complementary therapies?
This guide is provided for informational and educational purposes only. It does not constitute veterinary medical advice and is not a substitute for consultation with a qualified veterinarian. Every animal is unique and must be evaluated individually. If you have concerns about your cat's health, contact our clinic or consult a veterinarian promptly.
Did you find a lump on your cat?
Don't wait. Our team can evaluate the lesion, perform a rapid cytology, and guide you through the next steps, whether that means simple monitoring or a full oncology workup.