Hemangiosarcomas are malignant tumors derived from the cells lining blood vessels (hem = blood, angio = vessel, sarcoma = tumor).  Hemangiosarcoma is a common cancer in dogs accounting for approximately 5% of cases. Since blood vessels run throughout the body, hemangiosarcomas can develop anywhere. However, the most common sites are the skin, spleen, liver, and heart.  Most hemangiosarcomas (except some appearing in the skin) are both locally aggressive and have a high likelihood of spreading to other parts of the body. These tumors are typically filled with blood and very fragile.

Hemangiosarcoma Symptoms

Signs of hemangiosarcoma will vary depending on the location of the primary tumor. Dogs with hemangiosarcoma occurring inside the body may have symptoms related to blood loss into the abdomen or the space around the heart, resulting in weakness, lethargy, or pale gums. Golden retrievers, German shepherds, and Labrador retrievers are among the breeds most frequently diagnosed with hemangiosarcoma.

Dogs with cutaneous hemangiosarcoma may have a mass in or under the skin. Cutaneous hemangiosarcomas are found more frequently in light-skinned dogs and have been associated with sun exposure.

Diagnosis of Hemangiosarcoma in Dogs

In some cases, owners may bring their pet to the veterinarian with concerns of weakness and learn that a tumor has ruptured internally and requires urgent surgery.  Before surgery, it is essential to perform blood tests to evaluate blood cell numbers, blood clotting ability, and organ function. Information from X-rays of the chest and ultrasound of the abdomen will ensure that it will be safe to perform anesthesia and surgery and that there is no evidence of spread that is large enough to see. Dogs with visible metastasis may not benefit from surgery. Some dogs with hemangiosarcoma may require supportive care, such as fluid therapy or blood transfusions before surgery. If there is cancer in the spleen, patients with hemangiosarcoma may have problems related to irregular heart rhythm during or after surgery, which could require treatment as well.

Treatment and Prognosis of Hemangiosarcoma

Surgery is the primary method of treatment for most dogs with hemangiosarcoma, regardless of the location of the primary tumor. In most of these patients, the cancer will spread to other sites throughout the body 1-3 months after surgery. Chemotherapy delivered after surgery may delay metastasis. “Standard” chemotherapy typically consists of the drug doxorubicin (Adriamycin) given once every 2-3 weeks for a total of five treatments and is generally very well tolerated.

After completing chemotherapy, we recommend regular rechecks. Despite treatment, the long-term prognosis for dogs with hemangiosarcoma is generally poor.  Average survival times with surgery and chemotherapy are approximately 5-7 months, with only 10% of dogs surviving for one year.

Dogs with the subcutaneous (under the skin) form of hemangiosarcoma may do somewhat better than this average.

Dogs with hemangiosarcoma of the skin surface may have a better prognosis after surgery, but it depends on the appearance of the tumor under the microscope, and whether the entire tumor is removed with surgery.  Some dogs with hemangiosarcoma of the skin can be treated effectively and remain cancer-free for an extended period with surgery alone, while others do have the potential to metastasize (spread to other locations).

The Flint Animal Cancer Center also offers some therapies for hemangiosarcoma that have not been as thoroughly evaluated but may have the potential to be more effective than chemotherapy alone. For more information, please contact us at oncology@colostate.edu.

Treatment for Pets with Cancer

The Flint Animal Cancer Center’s comprehensive clinical practice offers advanced treatments in chemotherapy, surgery, and radiation for both common and rare cancers. If you are concerned that your pet might have cancer, the best first step is to schedule an appointment with your local veterinarian.