🔍 What Is Hemangiopericytoma?

Hemangiopericytoma is a rare vascular tumor arising from pericyte cells surrounding capillaries. These tumors grow locally, often beneath the skin of limbs or trunk, and are generally low to moderate in malignancy—but require prompt removal before invading surrounding tissue or organs. :contentReference[oaicite:3]{index=3}

🐾 How Common Is It in Cats?

While soft-tissue sarcomas make up ~7% of feline skin tumors, hemangiopericytomas are exceptionally rare—fewer than five well‑documented feline cases so far :contentReference[oaicite:4]{index=4}.

⚠️ Signs & Clinical Presentation

Owners may notice:

• A firm, slow-growing mass—often on a limb or trunk—possibly soft or fluctuant :contentReference[oaicite:5]{index=5}
• The mass may ulcerate or cause hair loss, skin discoloration, or soreness :contentReference[oaicite:6]{index=6}
• Rarely, bleeding may occur due to vascular involvement :contentReference[oaicite:7]{index=7}
• No systemic illness is common unless tumor grows near chest or abdomen :contentReference[oaicite:8]{index=8}

🧬 What Causes It?

The exact cause remains unknown—there are no confirmed viral or hereditary drivers. It’s thought to arise from spontaneous pericyte mutations :contentReference[oaicite:9]{index=9}.

🩺 Diagnostic Approach

• History & exam: note duration, growth, bleeding, location.
• Bloodwork & urine: typically normal, but assess overall health :contentReference[oaicite:10]{index=10}.
• Imaging: X‑rays, ultrasound, CT/MRI for deeper or chest-based tumors :contentReference[oaicite:11]{index=11}.
• Biopsy or FNA: establishes diagnosis and helps grade the tumor histologically :contentReference[oaicite:12]{index=12}.
• Histopathology & IHC: confirms pericyte origin—positive markers include vimentin and PDGFRβ; S‑100 may be variable :contentReference[oaicite:13]{index=13}.

💉 Tumor Grading & Staging

Pathologists grade tumors as low to high, based on cellular atypia, mitotic rate, necrosis, and invasiveness. Grading guides treatment—higher-grade tumors benefit more from aggressive management (surgery + radiation) :contentReference[oaicite:14]{index=14}.

✂️ Treatment Strategies

Surgery (First-Line)

Complete excision with wide margins is critical. Peripheral muscle removal helps reduce local recurrence risk :contentReference[oaicite:15]{index=15}.

Radiation Therapy

If clean margins aren’t feasible or tumor is high-grade, adjunctive radiation therapy is advised. In dogs, cure rates of 80–90% are possible—similar results are expected in cats :contentReference[oaicite:16]{index=16}.

Electrochemotherapy & Limb Amputation

Electrochemotherapy is an emerging option for inoperable tumors :contentReference[oaicite:17]{index=17}. For limb-based lesions that recur, amputation may be curative since metastasis is rare :contentReference[oaicite:18]{index=18}.

Palliative Radiation

If curative treatment is not possible or declines, palliative radiation may control local disease, reduce bleeding and prolong comfort :contentReference[oaicite:19]{index=19}.

Chemotherapy & Metronomic Therapy

Cats rarely receive systemic chemo for this tumor; however metronomic low-dose chemo (e.g., cyclophosphamide + piroxicam) may help slow growth :contentReference[oaicite:20]{index=20}.

📅 Prognosis & Follow-Up

• Low-grade, excised completely: excellent long-term control; recurrence rates are low.
• High-grade or incompletely excised: moderate recurrence risk—radiation improves outcomes :contentReference[oaicite:21]{index=21}.
• Metastasis: rare in cats, but documented in a small percentage :contentReference[oaicite:22]{index=22}.
• Palliative cases: radiation improves quality of life; survival varies depending on tumor location and growth rate.

Regular rechecks (every 3–6 months) with physical exams and imaging help identify recurrence early.

🐾 Guidance for Cat Parents

• 📍 Monitor for new lumps—notify your vet promptly.
• 📸 Photograph any mass to track changes in size or appearance.
• 🛡️ Support surgical and radiation recovery—minimize trauma and stress.
• 🍲 Maintain strong nutrition, hydration & gentle exercise.
• 📱 Lean on Ask A Vet for daily guidance, and support recovery with Woopf & Purrz calming tools.
• 🗓️ Schedule follow-up exams and imaging consistently.

📝 Summary Table