Hemangiomas usually appear as red-to-black nodules that may develop singularly or in multiple areas.  Sarcomas are cancers of connective tissue, blood vessels, or the fibrous tissue that surrounds and supports organs.  When used together, these two terms refer to hemangiosarcoma, which is a cancer of blood vessels, usually occurring in the spleen, heart or skin.

Hemangiosarcoma usually develops slowly and painlessly until it reaches an advanced stage. The disease can occur as a single tumor within one major organ or multiple tumors throughout the body.  According to the National Canine Cancer Foundation, advanced staged tumors “are resistant to most treatments.”  The normal therapy for this tumor is surgery and intensive chemotherapy.  Hemangiosarcoma occurs most commonly in large breed dogs with an age ranging from eight to 10 years.

The average time from discovery of the (hemangiosarcoma) tumor until death in affected dogs is six to eight weeks, but death can occur more rapidly in a number of cases.  This type of tumor is known to spread, or metastasize quickly.  Signs of the disease can range from subtle to overt, and may include unexplained weakness, nosebleeds, pale mucous membranes, abdominal swelling and depression, or collapse and sudden death.

Diagnosis often requires abdominal ultrasound, radiographs ("x-rays") of the chest, lab tests and exploratory surgery, though sometimes the tumor may be large enough to be felt during normal physical examination. 

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