Hemangiomas are "single to multiple, circumscribed, often compressible, red-to-black nodules," according to the Merck Veterinary Manual. "Whether these are neoplasms, hamartomas, or vascular malformations remains undefined, and no clear criteria exist that allow for their separation." Sarcomas are cancers of connective tissue, blood vessels, or the fibrous tissue that surrounds and supports organs such as the spleen. When used together, these two terms refer to "hemangiosarcoma," which is a cancer of blood vessels, usually occurring in the spleen, skin or heart.
According to the American College of Veterinary Surgeons (ACVS), splenic hemangiomas can have a similar clinical presentation to hemangiosarcoma (HSA) and, therefore, must be differentiated from HSA for proper treatment. To diagnose most effectively and accurately, veterinary surgeons recommend removal of the dog's spleen, rather than a biopsy, because the former is both a diagnostic and therapeutic procedure. Whether benign or malignant, the primary course of treatment for hemangiomas is usually surgical removal.
Hemangiosarcoma is known as a silent killer because it usually develops slowly and painlessly until it reaches an advanced stage. The disease can occur as a single tumour within one major organ or multiple tumours throughout the body. According to the National Canine Cancer Foundation, advanced staged tumours "are resistant to most treatments." The standard-of-care for this tumour is surgery and intensive chemotherapy. HSA occurs most commonly in large breed dogs eight to 10 years of age.
According to Canine Cancer Awareness.org, "A common estimate of the average time from discovery of the (hemangiosarcoma) tumour until death occurs in affected dogs is six to eight weeks, but death occurs more rapidly in a number of cases." The ACVS states that tumour spread, or metastasis, is "present in more than 80 per cent of dogs at presentation." Signs can range from subtle to overt, and may include unexplained weakness, nosebleeds, pale mucous membranes, abdominal swelling and depression, or collapse and sudden death.
Splenic hemangiomas and hemangiosarcomas can cause extremely large tumours--4.54 Kilogram or more. Therefore, veterinarians often locate these tumours upon physical exam. Tumours affecting other organs, such as the heart, can be very small and difficult to diagnose, often requiring radiographs, lab tests and exploratory surgery. Veterinarians may also aspirate fluid from the abdomen (abdominocentesis) and/or perform an abdominal ultrasound to identify masses. The ACVS also recommends an echocardiography (heart ultrasound) "as up to 15 per cent of dogs may have tumour spread to the right atrium on initial presentation."
The prognosis for hemangiomas depends on a number of factors, such as size and location. However, the prognosis for hemangiosarcoma is very poor. According to a study cited in the American Animal Hospital Association Journal, the media survival time of 32 dogs with Stage I or II hemangiosarcoma, treated by splenectomy alone, was only 86 days. With chemotherapy, the ACVS states that survival times only increase to 141 to 179 days.