Veterinary Guide to Canine Mesothelioma 2025 🩺🐶

By Dr. Duncan Houston BVSc

🧬 What Is Mesothelioma?

Mesothelioma is a rare malignant tumor originating from mesothelial cells lining body cavities—pleura, pericardium, peritoneum, or tunica vaginalis. It produces effusion and diffuse nodules, difficult to detect early.

📍 Types & Location

• Pleural mesothelioma – affects the lung lining; leads to pleural effusion and respiratory distress.
• Pericardial mesothelioma – in heart sac; causes pericardial effusion and may lead to tamponade.
• Peritoneal mesothelioma – abdominal involvement; leads to ascites, GI signs & discomfort.
• Tunica vaginalis/testicular – rare; may present as scrotal swelling.

⚠️ Risk Factors & Epidemiology

• Typically affects older dogs (4–13 yrs; mean ~8 yrs).
• Some breeds are at higher risk: German Shepherd, Irish Setter, Bouvier des Flandres.
• Environmental exposure—especially asbestos—is linked in some cases.
• Histological types: epithelial, sarcomatoid, or mixed; epithelial tends to respond better.

⚠️ Clinical Signs

• Pleural: dyspnea, cough, exercise intolerance due to pleural effusion.
• Pericardial: muffled heart sounds, ascites, collapse due to cardiac tamponade.
• Peritoneal: abdominal distension, lethargy, vomiting, anorexia.
• Systemic: weight loss, weakness, discomfort; effusion is often key finding.

🔍 Diagnostics & Confirmation

1. Imaging: chest/abdominal X-ray and ultrasound detect effusion, but nodules may be small.
2. Fluid analysis: cytology may show mesothelial cells, but distinguishing malignant from reactive is difficult.
3. Immunocytochemistry: helps differentiate malignant vs reactive cells; positivity for cytokeratin, vimentin, and desmin supports diagnosis.
4. Biopsy/Thoracoscopy: gold standard; obtain tissue for definitive histopathology.
5. Pericardial fluid pH: malignant effusions often pH >7.5.

🛠️ Treatment Strategies

1. Symptomatic Effusion Management

• Thoracentesis or pericardiocentesis to relieve dyspnea or tamponade.
• Repeated drainage may be needed as effusion recurs.

2. Chemotherapy

• Carboplatin, often alone or with gemcitabine, shows good efficacy in reducing effusion and extending survival.
• 5‑FU and mitoxantrone also used; chemo improved median survival from ~74 to ~234 days.
• Survival ranges 2–13 months; better outcome with early, responsive cases.

3. Surgery & Radiation

• Rarely feasible—tumor diffuses across serosa; surgery is typically palliative.
• Radiation therapy used cautiously; limited evidence of benefit.

4. Palliative & Supportive Care

• Pain control, nutritional support, rest, and comfort.
• Palliative care plan for advanced cases to support quality of life.

📈 Prognosis

• Generally poor, but chemotherapy significantly lengthens survival.
• Median survival: ~195 days overall; ~234 days with chemo vs ~29 days without.
• 1‑year survival: ~22%; depends on response and effusion control.
• Histologic subtype and early intervention influence outcomes.

📱 Ask A Vet Telehealth Support

• 📸 Share ultrasound & fluid images for remote assessment.
• 🔔 Alerts for drain schedule, chemo appointments, and rechecks.
• 🩺 Virtual follow-ups on breathing, appetite, and comfort levels.
  
• 🧠 fluid drainage, weight, and appetite trends.

🎓 Case Spotlight: “Roxy” the Labrador

Roxy, a 9‑year‑old Labrador Retriever, presented with recurrent pleural effusion. Ultrasound and cytology suspected mesothelioma. Carboplatin and gemcitabine therapy resolved effusion and improved comfort. Ask A Vet coordinated imaging, fluid removals, and tracked her recovery. She lived 11 months post‑diagnosis with good quality of life 🐾.

🔚 Key Takeaways

1. Canine mesothelioma is rare but should be considered with unexplained effusion.
2. Diagnosis relies on imaging, fluid cytology with IHC, and preferably biopsy.
3. Symptomatic relief from effusion is essential; chemotherapy (carboplatin±gemcitabine) prolongs survival.
4. Median survival ~6–8 months; chemo responders up to ~1 year with maintained quality of life.
5. Ask A Vet telehealth improves care with remote monitoring, scheduling, med delivery, and supportive care coordination 📲🐕

Dr Duncan Houston BVSc, founder of Ask A Vet. Download the Ask A Vet app to access expert telehealth support for mesothelioma—providing effusion management, coordinated chemotherapy, imaging reviews, and compassionate palliative care at home 🐶📲