Hemangiosarcoma (HSA)

If you are reading about Hemangiosarcoma (HSA), you might be going through a highly stressful and scary time with your dog. It is one of the toughest diagnoses a pet parent can face, but breaking down the medical jargon can help you understand exactly what is happening and what steps you can take.

What is Hemangiosarcoma (HSA)?

In short, HSA is a very aggressive, malignant cancer of the blood vessels. Because blood vessels run everywhere in the body, this cancer can form anywhere, but it most commonly targets blood-rich organs:

The Spleen (most common)
The Heart
The Liver

Why is it so dangerous? The tumors made by HSA are incredibly fragile. Think of them like thin blisters filled with blood. Because they are weak, they can easily rupture (burst) without warning. When a tumor bursts, it causes internal bleeding, which is why dogs often seem fine one day and suddenly collapse the next.

Symptoms: What to Watch For

HSA is often called a “silent killer” because internal tumors rarely cause pain or signs of illness until they rupture. Symptoms depend entirely on where the cancer is located.

1. Internal (Visceral) HSA

This is the hidden form. If a tumor ruptures internally, your dog will experience sudden blood loss. Seek emergency veterinary care immediately if you notice:

Sudden collapse or extreme weakness.
Pale or white gums (instead of a healthy pink).
Rapid or heavy breathing.
A swollen, pot-bellied abdomen (caused by blood pooling in the belly).
Lethargy that comes and goes (sometimes a small bleed stops on its own, and the dog temporarily “rallies”).

2. Skin (Cutaneous) HSA

This form is visible on the outside of the body. Look for:

Red, purple, or dark bumps and patches on the skin.
Areas that bruise or bleed spontaneously.

Who is Most at Risk?

While any dog can develop HSA, it primarily affects older, large-breed dogs.

Top At-Risk Breeds: Golden Retrievers, German Shepherds, and Labrador Retrievers.
Sun Exposure Risk: The skin form of HSA is heavily linked to UV sunlight and is most common in short-haired, light-skinned dogs who love to sunbathe on their backs.
The Cause: For internal tumors, the exact cause is unfortunately unknown. It is not caused by anything you did or didn’t do.

How is HSA Diagnosed?

Because it is so stealthy, HSA is usually discovered during an emergency room visit after a dog collapses, or by chance during a routine vet checkup. To get a clear picture, a vet will typically run:

Blood work & Clotting Tests: To check for anemia (low red blood cells) and see how well the blood clots.
X-rays & Abdominal Ultrasounds: To look for masses on the spleen or liver and check for fluid (blood) in the abdomen.
An Echocardiogram: A specialized ultrasound of the heart to see if a tumor is present there.
Biopsy: Taking a tissue sample is the only way to 100% confirm the cancer is HSA.

Treatment Options & Prognosis

Tragically, there is no cure for internal HSA. Treatment is focused on preventing life-threatening bleeding and buying you more comfortable, high-quality days with your dog.

Treatment Paths

Surgery: If the tumor is on the spleen, removing the entire spleen (splenectomy) is the quickest way to stop immediate bleeding.
Chemotherapy: Given after surgery to slow down the spread of the cancer. A drug called doxorubicin is commonly used.
Supportive Care: Vets often prescribe a Chinese herbal supplement called Yunnan Baiyao, which helps the blood clot and controls minor bleeding.

Expectation & Lifespan

Internal HSA (Spleen/Heart): Even with surgery and chemotherapy, the average life expectancy is 4 to 6 months, and less than a year for most dogs. Without treatment, it is often a matter of days to weeks.
Skin HSA: There is much better news here. If the tumor is strictly on the surface of the skin, completely removing it with surgery can often cure the dog entirely.

What You Can Do Next

If your dog has been diagnosed or you suspect HSA, time is of the essence. You may want to consult a board-certified veterinary oncologist (a cancer specialist) to discuss the newest treatments, such as experimental clinical trials (like eBAT therapy) that are working to extend a dog’s survival time.

Tip: You can use the ACVIM Board Certified Specialist Finder to locate a canine cancer expert near you.

How to cope with your dog having Hemangiosarcoma

Finding out your dog has Hemangiosarcoma (HSA) is devastating. Because this cancer is so aggressive and unpredictable, coping with the diagnosis is as much about managing your own emotional well-being as it is about caring for your dog.

1. Shift from “Curing” to “Comfort” (Palliative Care)

Accepting that HSA cannot be cured is the hardest but most necessary step. Once you shift your focus, you can dedicate your energy to making every single day count.

Focus on Quality of Life: Watch your dog’s daily happiness. Are they enjoying meals? Do they still love a gentle scratch behind the ears?
Spoil Them Rotten: Now is the time for the “bucket list.” If they love a specific human food that won’t upset their stomach (like a bit of plain roasted chicken), let them have it. Take them to their favorite park, even if they just sit on a blanket and sniff the air.

2. Prepare an Emergency Plan

Because internal HSA tumors can rupture without warning, having a plan reduces panic if a crisis happens.

Keep Emergency Numbers Handy: Save the number, address, and directions to the nearest 24/7 emergency veterinary hospital in your phone and on your fridge.
Know the Red Flags: Re-familiarize yourself with the signs of an internal bleed—sudden weakness, heavy panting, cold paws, and pale or white gums. Checking your dog’s gums daily will give you a baseline of what their healthy, pink color looks like.
Have a Transport Plan: If your dog is large, think about how you will safely lift them into the car if they suddenly collapse (e.g., using a large blanket as a makeshift stretcher).

3. Manage the “Anticipatory Grief”

Anticipatory grief is the pain you feel before a loss happens. With HSA, pet parents often live in constant fear, wondering, “Is today the day?”

Don’t Let Fear Steal the Present: It is incredibly easy to spend all your time crying over your dog while they are sitting right next to you, feeling okay. Try to remind yourself: Right now, in this exact moment, my dog is here, comfortable, and loved. Dogs live in the present; try to meet them there.
Take Tons of Photos and Videos: Capture the happy moments, the way they sleep, and the sound of their bark. You will treasure these later.

4. Define Your “Line in the Sand”

HSA can progress very rapidly. To avoid making agonizing decisions during an emergency, sit down now—when you are calm—and decide what your boundaries are for your dog’s care.

Ask Yourself Critical Questions: * How many emergency surgeries am I willing to put them through?
- What does a “bad day” look like? (e.g., if they refuse to eat for 48 hours, or if they can no longer stand up on their own).
Track the Good vs. Bad Days: Use a calendar to mark each day as “Good,” “Average,” or “Bad.” When the bad days begin to outnumber the good ones, or when your dog loses interest in the things they love, it is a loving sign that it may be time to consider euthanasia.

5. Lean on a Support System

You do not have to carry this heavy burden alone.

Talk to Your Vet: Be open with your veterinarian about your fears. They can provide guidance on pain management and what to expect in the final stages.
Seek Pet Loss Support Groups: There are many online forums and social media support groups specifically for pet parents dealing with canine hemangiosarcoma. Talking to people who truly understand the unique, ticking-clock anxiety of HSA can be incredibly comforting. Pet Vet Corner offers a group called PVC- One Day At A Time Pet Support For Terminally ill and Elderly Pet. https://www.facebook.com/groups/pvconedayatatimepetsupportoriginal or our PVC Pet Loss group when your final day has arrived, this group of wonderful members can offer you the support needed. https://www.facebook.com/groups/pvccopingoriginal

Keep in mind, Your dog doesn’t know they are sick; they only know how they feel right now, and they know that you love them. Be gentle with yourself as you navigate this road.

This information is not to take the place of a hands on veterinarian, we encourage you to establish a relationship with your local veterinarian.