Synovial Sarcoma in Cats: Expert Vet Guide 🐱🩺 2025

By Dr Duncan Houston BVSc, veterinarian & founder of Ask A Vet

Synovial sarcoma is a rare but aggressive malignant soft tissue tumor affecting tissues around joints and tendon sheaths in cats. While uncommon, prompt recognition and combined surgical and medical treatment can improve outcomes and comfort for affected cats. This expert 2025 guide covers:

• 🔍 What synovial sarcoma is and how it behaves
• 🧬 Risk factors & incidence in feline patients
• 🚨 Clinical signs such as lameness, swelling, and pain
• 🧪 Diagnostic protocols—imaging, biopsy, staging
• 💉 Treatment strategies including surgery, radiation, chemotherapy
• 📆 Prognosis & recurrence risk
• 🤝 How Ask A Vet telehealth supports diagnosis & recovery

🔍 What Is Synovial Sarcoma?

Synovial sarcoma is a malignant soft tissue sarcoma arising near joints, tendon sheaths, or bursae—despite the misleading name, tumor cells don’t originate from synovial tissue. In cats, these tumors are extremely rare but among the most common primary joint tumors reported :contentReference[oaicite:2]{index=2}.

🧬 Incidence & Risk Factors

• Rare in cats—only a handful of cases described (<5 documented metastatic cases) :contentReference[oaicite:3]{index=3}.
• Affects middle-aged to older cats, no clear breed or sex predisposition.

🚨 Clinical Signs

• Lameness or limping, often progressive :contentReference[oaicite:4]{index=4}.
• Swelling or palpable mass near active joints.
• Pain on joint manipulation or stance shifts.
• Reduced range of motion or stiffness.
• Signs of systemic illness: weight loss, reduced appetite, lethargy in advanced cases, or when metastasis occurs :contentReference[oaicite:5]{index=5}.
• Possible respiratory signs if lung metastasis develops :contentReference[oaicite:6]{index=6}.

🧪 Diagnostic Workup

1. Physical exam: assess joint swelling, palpate mass, check lymph nodes.
2. Imaging:
   • X‑rays—to detect soft tissue swelling, periosteal changes :contentReference[oaicite:7]{index=7}.
   • Ultrasound—heterogeneous mass evaluation :contentReference[oaicite:8]{index=8}.
   • CT/MRI for surgical planning and staging advanced disease :contentReference[oaicite:9]{index=9}.
3. Biopsy: essential for definitive diagnosis. Core or excisional biopsy with histopathology differentiates synovial sarcoma from other sarcomas :contentReference[oaicite:10]{index=10}.
4. Staging: chest X-rays or CT for pulmonary metastases (up to ~30% of cases), regional lymph node evaluation :contentReference[oaicite:11]{index=11}.
5. Immunohistochemistry: confirms sarcoma subtype—tumor positivity for vimentin/epithelial markers and absence of markers for melanoma or nerve sheath tumors :contentReference[oaicite:12]{index=12}.

💉 Treatment Options

1. Surgical Removal

• Wide surgical excision or amputation for limb-associated tumors is first-line :contentReference[oaicite:13]{index=13}.
• Aim for clear margins due to high local recurrence risk.

2. Radiation Therapy

• Considered for incomplete resections or unresectable sites—helps reduce recurrences :contentReference[oaicite:14]{index=14}.

3. Chemotherapy

• Doxorubicin-based protocols often recommended due to soft tissue sarcoma behavior :contentReference[oaicite:15]{index=15}.
• Used as adjuvant therapy post-surgery or for metastatic disease.

4. Palliative Care

• Rehabilitation, analgesia, anti-inflammatories, and supportive fluids.
• Palliative radiation can help reduce mass effect and discomfort.

📆 Prognosis & Outcomes

• Prognosis variable—good with complete surgery and no metastasis.
• Metastasis in ~25–60% of cases—primarily to lungs or lymph nodes :contentReference[oaicite:16]{index=16}.
• Reported survival times range from ~10 months (metastatic) to beyond 12–18 months with aggressive treatment :contentReference[oaicite:17]{index=17}.
• Regular rechecks and imaging help detect recurrences early.

🤝 Ask A Vet Telehealth Support

Our telehealth service empowers you through every phase:

• 📸 Evaluate swelling and lameness severity—help plan diagnostic urgency.
• 💬 Guide imaging preferences (X‑ray vs ultrasound vs CT/MRI).
• 📅 Assist with surgical referral and recovery planning.
• 💊 Advise on pain management, chemo side effects, and home care.
• 🔄 Monitor for recurrence or systemic signs and advise on staging/retreatment.

✅ Key Takeaways

• Synovial sarcoma is a rare but aggressive joint tumor in cats.
• Signs include swelling, lameness, pain, and occasional respiratory signs.
• Diagnosis requires imaging and biopsy confirmation.
• Treatment involves surgery ± radiation or chemotherapy.
• Metastasis risk is moderate—close monitoring is essential.
• Ask A Vet offers telehealth support from diagnosis to long-term monitoring.

📞 Final Thoughts

Although synovial sarcoma in cats is uncommon, its aggressive nature mandates a thorough approach: timely diagnosis, surgical treatment, and vigilant follow-up. With the right care and Ask A Vet telehealth support, owners can navigate treatment confidently, optimizing their cat’s comfort and longevity. 😊💜

Noticing joint swelling or limping in your cat? Get prompt support via AskAVet.com and the Ask A Vet app for expert telehealth guidance anytime!