Hemangiosarcoma In Dogs

Golden Retrievers are substantially overrepresented among hemangiosarcoma patients. The Golden Retriever Lifetime Study evaluates them for osteosarcoma as well as hemangiosarcoma.

Hemangiosarcoma (HSA) is a common cancer of dogs, usually occurring beyond middle age and the following breeds are most frequently afflicted: Golden Retrievers, German Shepherds, Portuguese Water Dogs and Skye Terriers.
Hemangiosarcoma is one of the cancers being studied in the Golden Retriever Lifetime Study. Roughly 20% of Golden Retrievers will suffer from hemangiosarcoma in their lifetimes.

Although it is a long word, hemangiosarcoma can be understood by looking at the etymology: “Hemo” is from the Greek haima or haimatos meaning “blood.” “Angio” is from the Greek prefix angeion, meaning “vessel.” “Sarco” comes from the Greek combining form sarcos meaning “flesh” or “body.” Dorland’s Medical Dictionary defines sarcoma as “a tumor made up of a substance like the embryonic connective tissue; tissue composed of closely packed cells embedded in a fibrillar or homogeneous substance. Sarcomas are often highly malignant.”

We often oversimplify the explanation of hemangiosarcoma by saying “it is a tumor composed of blood vessels.” Actually, the body has made an even more serious mistake, because the mass will consist of endothelial cells and a fibrous component. Endothelial is the adjective form of the noun endothelium, which is the lining of the inside of blood vessels. It comes from the Greek prefix endo, meaning “inside,” and thele, meaning “nipple.”

Not surprisingly, endothelial cells arise from the bone marrow, where most red and white blood cells originate. Starting as stromal cells, they differentiate in several stages into cells lining the inside of every blood vessel.


HSA typically is found in the spleen, right atrium of the heart and skin. Hidden deep inside the body, it has usually progressed far beyond treatment by the time it is observed.


Most of these patients expire due to fatal hemorrhage. Because the cancerous endothelial cells are imperfect, they are fragile and subject to failure.

Some patients experience small bleeding episodes, resulting in weakness, fainting and lethargy. If the tumor is in the spleen, the abdomen can swell and contain a large amount of blood with no other signs.

Bleeding from a tumor on the right atrium may fill the pericardium (sac surrounding the heart). If the bleeding volume results in pressure becoming great enough to interfere with cardiac function, the patient may become weak, with low pulse strength and rapid, labored breathing. A larger volume of bleeding may so compress the heart that it is unable to pump, and circulation failure occurs. If the pericardium ruptures and blood escapes into the chest, lungs may be compressed, again resulting in difficult breathing, but with stronger pulses unless a critical volume of blood has escaped.

Stopping an internal bleeding episode is impossible.

There is little to be done therapeutically for visceral hemangiosarcoma patients, as the masses do not lend themselves to surgical removal and frequently will have metastasized to other organs by the time of initial diagnosis.  Chemotherapy can extend lifespan minimally, with median survival time about six months.


The cutaneous (skin) form can respond to surgical resection, and its tendency to metastasize (spread) has been found in one study to be proportional to its depth in the skin; i.e., deeper lesions are more likely to show up again in the same or a new location.  Chemotherapy is somewhat more helpful in cutaneous hemangiosarcoma compared to the visceral form.

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