|Classification and external resources|
Hemangiosarcoma is a rapidly growing, highly invasive variety of cancer, occurring almost exclusively in dogs and rarely in cats. It is a sarcoma arising from the lining of blood vessels that is blood-filled channels and spaces are commonly observed microscopically. A frequent cause of death is the rupturing of this tumor causing the patient to rapidly bleed to death.
The term angiosarcoma, when used without modifier, usually refers to hemangiosarcoma. However, glomangiosarcoma (8710/3) and lymphangiosarcoma (9170/3) are distinct conditions. Hemangiosarcomas are commonly associated with toxic exposure to thorium dioxide (Thorotrast), vinyl chloride, and arsenic.
Hemangiosarcoma in dogs 
Hemangiosarcoma is quite common in dogs, and more so in certain breeds of dogs including German Shepherds and Golden Retrievers. It also occurs in cats, but is much rarer. Dogs with hemangiosarcoma rarely show clinical signs until the tumor has become very large and has metastasized. Typically, clinical signs are due to hypovolemia after the tumor ruptures, causing extensive bleeding. Owners of the affected dogs often discover that the dog has hemangiosarcoma only after the dog collapses.
The tumor most often appears on the spleen, right heart base, or liver, although varieties also appear on or under the skin or in other locations. It is the most common tumor of the heart, and occurs in the right atrium. Here it can cause right-sided heart failure, arrhythmias, pericardial effusion, and cardiac tamponade. Hemangiosarcoma of the spleen or liver is the most common tumor to cause hemorrhage in the abdomen. Hemangiosarcoma of the skin usually appears as a small red or bluish-black lump. It can also occur under the skin. It is suspected that in the skin, hemangiosarcoma is caused by sun exposure. Occasionally, hemangiosarcoma of the skin can be a metastasis from visceral hemangiosarcoma. Other sites the tumor may occur include bone, the kidney, the bladder, muscle, the mouth, and the central nervous system.
Clinical features 
Presenting complaints and clinical signs are usually related to the site of origin of the primary tumor or to the presence of metastases, spontaneous tumor rupture, coagulopathies, or cardiac arrhythmias. More than 50% of patients are presented because of acute collapse after spontaneous rupture of the primary tumor or its metastases. Some episodes of collapse are a result of ventricular arrhythmias, which are relatively common in dogs with splenic or cardiac HSA.
Most common clinical signs of visceral hemangiosarcoma include loss of appetite, arrhythmias, weight loss, weakness, lethargy, collapse, pale mucous membranes, and/or sudden death. An enlarged abdomen is often seen due to hemorrhage. Metastasis is most commonly to the liver, omentum, lungs, or brain.
A retrospective study published in 1999 by Ware, et al., found a five times greater risk of cardiac hemangiosarcoma in spayed vs. intact female dogs and a 2.4 times greater risk of hemangiosarcoma in neutered dogs as compared to intact males.
Clinicopathologic findings 
HSAs usually cause a wide variety of hematologic and hemostatic abnormalities, including anemia; thrombocytopenia; presence of nRBC, schistocytes, and acanthocytes in the blood smear; and leukocytosis with neutrophilia, left shift, and monocytosis.
A definitive diagnosis requires biopsy and histopathology.
Treatment includes chemotherapy and, where practical, removal of the tumor with the affected organ, such as with a splenectomy. Splenectomy alone gives an average survival time of 1–3 months. The addition of chemotherapy, primarily consisting of the drug doxorubicin, alone or in combination with other drugs, can increase the average survival time to 5–7 months.
Visceral hemangiosarcoma is usually fatal even with treatment, and usually within weeks or, at best, months. In the skin, it can be cured in most cases with complete surgical removal as long as there is not visceral involvement.
See also 
Using herbal medicines have been adopted by many holistic veterinary practitioners and oncology vet specialists in combination with conventional chemotherapy or alternatively when surgery or chemotherapy are not suitable.
On September 10, 2012, Dorothy Cimino Brown and Jennifer Reetz , two doctors from University of Pennsylvania School of Veterinary Medicine were published in Evidence-Based Complementary and Alternative Medicine Volume 2012 (2012), Article ID 384301, 8 pages doi:10.1155/2012/384301 for a research article on "Single Agent Polysaccharopeptide Delays Metastases and Improves Survival in Naturally Occurring Hemangiosarcoma" The study found that the mushroom extract "I'm-Yunity" used in the study is able to delay the progression of metastases and provide the longest median survival times reported to date.
- American Kennel Club Canine Health Foundation. Accessed 2012-12-06
- Ettinger, Stephen J.;Feldman, Edward C. (1995). Textbook of Veterinary Internal Medicine (4th ed. ed.). W.B. Saunders Company. ISBN 0-7216-6795-3.
- Morrison, Wallace B. (1998). Cancer in Dogs and Cats (1st ed. ed.). Williams and Wilkins. ISBN 0-683-06105-4.
- Nelson et al. Manual of Small Animal Internal Medicine. Elsevier Mosby: St. Louis, Missouri (2005)
- Compound Derived From a Mushroom Lengthens Survival Time in Dogs With Cancer, Penn Vet Study Finds
- Hemangiosarcoma research at the Modiano Lab of the Univ. of Minnesota - includes links to other canine cancer research
- Vetinfo on Hemangiosarcoma
- Canine Cancer Awareness on Hemangiosarcoma, including more links to current studies
- Flat-Coated Retriever Hemangiosarcoma page
- Vet Corner on Hemangiosarcoma
- Mar Vista Animal Medical Center on Hemangiosarcoma
- Hemangiosarcoma in Cats and Dogs from Pet Cancer Center
- Heart hemangiosarcoma in Cats and Dogs from Pet Cancer Center