Hemangiosarcoma (HAS for short) is a from of cancer that is fairly common in dogs.  There are three basics forms of HAS: dermal (skin), hypodermal (under the skin), and visceral (splenic or cardiac).  While the visceral form is most common, dermal and hypodermal have been recently studied in detail.  HAS is highly metastatic, and most forms of the disease are associated with a poor prognosis.  The dermal form can potentially be cured with surgery alone, and many dogs may have a fair to excellent long-term prognosis.

Dermal and Hypodermal HAS account for 14% of all reported HAS. Dermal HAS often appears as a dark to purple skin lesion, which may be raised and appear on non-haired areas like the abdomen.  Hypodermal HAS can occur anywhere on the body and may appear as a soft mass or be a firm invasive mass with ulceration.  30% of all dogs with dermal HAS develop metastatic disease, while 60% of dogs with hypodermal HAS develop metastatic disease.

Visceral HAS accounts for 2% of all reported malignancies and up to 5% of all noncutaneous tumors in dogs.  Although these numbers seem small, they have a significant impact on dogs, since this form of cancer kills.  The spleen and the right atrium of the heart are the most common sites of occurrence of visceral HAS.  Dogs may have nonspecific signs such as lethargy, loss of appetite, weight loss or more specific signs such as difficulty breathing, pallor, or abdominal fluid.  Regardless of the site of origin, visceral HAS is locally invasive and highly metastatic.  Up to 25% of dogs with splenic HAS have cardiac HAS and up to 63% of dogs with atrial HAS have metastatic disease.  Metastases commonly affect the lover, mesentery, lungs, and brain.

As with any malignancy, it is important to determine the extent of the disease.  Even when spread of the cancer is not evident by eye, there is often microscopic spread at the time of diagnosis, therefore chemotherapy is recommended along with surgery.  Since visceral HAS can metastasize to the skin , a dog with dermal or hypodermal HAS should be 'staged'.  Staging involves doing bloodhwork, urinalysis, abdominal and chest x-rays, EKG, and ultrasound.  The staging of the tumor is closely linked to prognosis.  Dermal HAS has a 780 day mean survival time with surgery alone.  Hypodermal HAS has only a 172 day mean survival time with surgery alone and chemotherapy is recommended.  Visceral HAS has up to 65 day survival with surgery alone, and up to 6 months survival time with surgery and chemotherapy.  A single agent chemotherapy is currently recommended .  Combination  chemotherapy was long thought to be the best , but recent studies show doxorubicin based therapy to have the same survival statistics.  Immunotherapy is not yet commercially available, but shows promise in the near future for increased survival times.

The prognosis for dogs with HAS is guarded.  Because it is so highly metastatic, dogs should be treated with surgery to remove any visible tumor and chemotherapy to treat any microscopic disease.  Ultimately, metastatic disease occurs, chemotherapy resistance develops and available treatment modalities fail.  Although cancer of any form is a frustrating and heartbreaking disease, treatment with surgery and chemotherapy is well tolerated  and provides prolonged survival time and an enhanced quality of life.