🐾 Hemangiosarcoma in Dogs and Cats: 2025 Veterinary Guide to Blood & Skin Cancer 🩸

By Dr Duncan Houston, BVSc

Hemangiosarcoma is a malignant cancer of blood vessel cells 🩸. While the skin form can often be surgically removed with success ✂️, internal forms—like those found in the spleen or around the heart—are more dangerous due to their tendency to bleed internally and spread rapidly. 🏥

🔬 What Is Hemangiosarcoma?

This cancer arises from perivascular endothelial cells—those that line the inside of blood vessels. Hemangiosarcoma can appear anywhere in the body where blood vessels are found, but it tends to target three primary locations:

• 🌞 Skin and subcutaneous tissues
• 🩺 Spleen
• ❤️ Heart (typically right atrium)

🩹 Skin Hemangiosarcoma in Dogs

✅ Dermal Form

This form often shows up as red to black growths on areas with little hair, such as the belly. It’s common in white or light-haired breeds like Dalmatians and pit bull types, and is linked to sun exposure ☀️.

Prognosis: Fair, especially if removed early before invading deeper tissue.

⚠️ Subcutaneous (Hypodermal) Form

Though under normal-looking skin, these tumors are far more dangerous and often appear unexpectedly during removal surgery. 60% of cases spread internally.

Median survival time with surgery only: ~6 months.

🔍 Diagnostic Steps for Skin Tumors

If your dog’s biopsy reveals hemangiosarcoma, your vet may recommend “staging” to determine how far it has spread:

• 📸 Chest radiographs to detect lung metastases
• 🩻 Abdominal ultrasound for splenic involvement
• 🫀 Cardiac ultrasound to check for heart tumors

🪫 Splenic Hemangiosarcoma

The spleen, when harboring this cancer, can rupture suddenly, causing internal bleeding 😔. Removal of the spleen (splenectomy) may save the dog’s life—but a diagnosis of malignancy will require follow-up therapy.

Key Statistics:

• 🧬 60% malignant hemangiosarcoma vs 40% benign hemangioma in splenic cases
• 💉 Median survival time: 19–86 days with surgery only
• 🧪 With chemo: 3–6 months survival average

Ask your vet about metronomic chemotherapy 🧴, which uses lower doses with fewer side effects.

🪷 Herbal Support: Yunnan Baiyo

This Chinese herbal product may reduce bleeding risks for dogs that aren’t surgical candidates. It comes in powder or capsule form and is sometimes used in hospice care for comfort. Discuss with your vet before use 🩹🌿.

🫀 Heart-Based Hemangiosarcoma

These tumors typically sit near the right atrium and cause dangerous bleeding into the pericardial sac, leading to pericardial tamponade—a life-threatening emergency 🚨.

What You’ll See:

• 😴 Lethargy and collapse
• 💨 Trouble breathing
• 🩸 Shock signs

Survival with surgery only: 1–3 months ⌛
With surgery + chemo: up to 6 months 🧬

🧬 Chemo Protocols and Research

Modern chemo uses doxorubicin (Adriamycin) every 3 weeks and oral cyclophosphamide. There's also ongoing research into immunotherapy 🧪 and anti-angiogenic treatments to block tumor blood supply—ask your vet if your dog might qualify for trials or studies 📋.

🐱 Hemangiosarcoma in Cats

Less common than in dogs but still serious, feline hemangiosarcoma comes in several forms:

• 😼 Dermal (skin)
• 😾 Subcutaneous (under the skin)
• 🩺 Visceral (organs)
• 👄 Oral (gums and mouth)

Best outcomes occur with early surgical removal of dermal tumors. Subcutaneous tumors have a 60% recurrence rate, and visceral types are often fatal at diagnosis 😿.

Mitotic Figures Matter

The more cells actively dividing (i.e., mitotic figures), the more aggressive the tumor. Ask your vet about the mitotic index in your cat’s pathology report 🔬.

⚖️ Final Thoughts from Dr Duncan Houston

Hemangiosarcoma is a devastating diagnosis, but not always without hope 💛. Whether you’re dealing with a skin form that’s easy to treat or a dangerous splenic or cardiac tumor, staying informed helps you make the best decisions for your pet. Early detection and prompt veterinary care are key 🕵️‍♂️.

Need help understanding your dog’s diagnosis or getting a second opinion?
Visit AskAVet.com or download the Ask A Vet app 📱 for access to licensed veterinary professionals and personalized pet care support 🐾.