🐶🐱 Mast Cell Tumors in Dogs & Cats: A 2025 Veterinary Guide by Dr. Duncan Houston

By Dr. Duncan Houston BVSc

Mast cell tumors (MCTs) are among the most prevalent skin cancers in our canine and feline companions. Understanding their nature, diagnosis, and treatment options is crucial for ensuring the best outcomes for our pets. 🩺

🔬 What Are Mast Cell Tumors?

Mast cells are a type of white blood cell involved in allergic responses and inflammation. When these cells proliferate abnormally, they can form tumors, commonly found in the skin but also in internal organs. These tumors can release histamine and other substances, leading to various symptoms. 🧬

🐕 Mast Cell Tumors in Dogs

📊 Prevalence and Risk Factors

• MCTs account for approximately 16-21% of skin tumors in dogs.
• Breeds with higher risk include Boxers, Pugs, Boston Terriers, and Shar-Peis.
• Typically diagnosed in middle-aged to older dogs.

🩺 Clinical Signs

• Single or multiple skin nodules, which may be red, ulcerated, or swollen.
• Lesions that change size rapidly (Darier's sign).
• Gastrointestinal symptoms like vomiting or loss of appetite due to histamine release.

🧪 Diagnosis

• Fine-needle aspiration (FNA) for cytology to identify mast cells.
• Biopsy for histopathological grading.
• Staging tests: blood work, abdominal ultrasound, and chest radiographs to assess metastasis.

🧬 Grading Systems

Two primary grading systems are used:

• Patnaik System: Grades I (well-differentiated), II (intermediate), and III (poorly differentiated).
• Kiupel System: Simplifies grading into low-grade and high-grade tumors, providing clearer prognostic information.

💊 Treatment Options

• Surgical Excision: Primary treatment for localized tumors. Wide margins are essential due to the infiltrative nature of MCTs.
• Radiation Therapy: Used post-surgery if margins are incomplete or for inoperable tumors.
• Chemotherapy: Agents like vinblastine and lomustine are used, especially for high-grade or metastatic tumors.
• Tyrosine Kinase Inhibitors: Toceranib phosphate (Palladia) targets specific mutations in mast cells.
• Stelfonta® (tigilanol tiglate): An injectable treatment causing tumor necrosis, approved for certain MCTs.
• Supportive Care: Antihistamines and gastroprotectants to manage systemic effects of histamine release.

📈 Prognosis

• Low-grade tumors: With complete excision, prognosis is excellent, with many dogs achieving long-term remission.
• High-grade tumors: More aggressive, with a higher chance of metastasis. Median survival times vary, often requiring multimodal treatment.

🐈 Mast Cell Tumors in Cats

📊 Prevalence and Forms

• Second most common skin tumor in cats.
• Two main forms: cutaneous (skin) and visceral (internal organs like spleen and intestines).

🩺 Clinical Signs

• Cutaneous MCTs: Nodules on the head, neck, or limbs.
• Visceral MCTs: Symptoms include vomiting, weight loss, and lethargy.

🧪 Diagnosis

• FNA and biopsy for skin tumors.
• Imaging (ultrasound) and FNA for internal tumors.

💊 Treatment Options

• Surgical Removal: Effective for solitary cutaneous tumors.
• Splenectomy: For splenic MCTs, can lead to significant improvement.
• Chemotherapy: Used for disseminated disease; protocols vary.
• Supportive Care: Similar to dogs, managing systemic effects.

📈 Prognosis

• Cutaneous MCTs: Generally good prognosis with surgical removal.
• Visceral MCTs: Prognosis varies; cats with splenic involvement and good appetite at diagnosis have better outcomes.

🧭 Navigating Treatment Decisions

Deciding on the best course of action involves considering the tumor's grade, location, and whether it has spread. Collaboration with a veterinary oncologist can provide tailored treatment plans. 🩺

📱 Need Support?

For personalized advice and support, visit AskAVet.com or download the Ask A Vet app. Our team is here to help you navigate your pet's health journey. 🐾

Stay informed and proactive in your pet's care. Early detection and treatment are key to better outcomes. 🐶🐱