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Hemangiosarcoma

Hemangiosarcoma is a malignant, rare, rapidly growing, highly invasive variety of cancer. It is a blood-fed sarcoma; that is, blood vessels grow directly into the tumor and it is typically filled with blood. A frequent cause of death is the rupturing of this tumor, causing the victim 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.

Stewart-Treves syndrome is a form of hemangiosarcoma due to lymphedema, usually following mastectomy and radiotherapy for breast cancer.

Hemangiosarcoma in dogs

Hemangiosarcoma is somewhat 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 more rare. Dogs with hemangiosarcoma rarely show clinical signs until the tumor has become very large and has metastasized. Typically, clinical signs are due to hypovolaemia 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 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.

Hemangiosarcoma can cause anemia, thrombocytopenia (low platelet count), and disseminated intravascular coagulation (DIC). 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.

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.

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