Canine Hemangiosarcoma

Canine Hemangiosarcoma

By Dr. Ed Mapes
Stonebridge Animal Hospital
McKinney, Tx

“Some days you get the bear, and sometimes the bear gets you”. Veterinary medicine is for the most part a very rewarding profession. I manage to leave the hospital on most days satisfied that we were able to help a number of animals, and sometimes save a life or two – I tell our staff on those occasions that “we got the bear today”.
Dogs afflicted with hemangiosarcoma (HSA), a malignant form of cancer known to spread aggressively, often prove to be among the most difficult cases: those that in spite of the most diligent efforts and best techniques available, we’re unable to save an animal. These are the depressing days when the bear gets us.
Reports estimate that anywhere from 1/2 to 2/3 of splenic masses (growths or tumors of the spleen) are malignant tumors, and the majority of these are hemangiosarcomas (HSA). HSA is a malignant neoplasm that arises from the inner wall of blood vessels that is known to spread early and aggressively (Figure 1). This neoplasm can arise in any tissue – since it originates from blood vessels – but the spleen is the most common site of tumor development in the dog, accounting for 50 to 65% of all canine HSA. This is also the most common tumor of the canine heart, and is also found as skin growths.

Insert Figure 1
Figure 1 during this surgery we see that hemangiosarcoma has involved the liver, making the prognosis very unfavorable for this patient.
These cases can be particularly heartbreaking because clinical signs in dogs are usually very subtle – offering little warning even though the neoplasia grows and spreads – until the dog finally develops recognizable symptoms. These dogs often proceed from being presumably very healthy to having a diagnosis of a potentially serious cancer the very next day.
Subtle clinical signs include weakness, increased thirst, vomiting, gradual loss of appetite, abdominal distention, rapid heart and breathing rates, pale mucous membranes and weight loss. If I see these symptoms in a middle aged or older dog that is medium to larger size, I automatically include HSA in my list of possible diseases.
German shepherds are reported to be more susceptible to this tumor than most dog breeds, but I’ve seen HSA in many breeds; recent cases have included two golden retrievers and two Australian Shepherds.

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Patients can look very much like this wonderful dog, but have a deadly cancer growing inside.

We run tests to determine the cause of symptoms in these situations, and we proceed accordingly if indications point toward HSA. This usually involves surgery to remove the affected tissue and submit for biopsy.
If diagnosed early enough, we can get to the splenic tumor before it ruptures and begins to bleed. In these cases, we search the abdominal cavity for evidence of tumor spread, and contact the owner directly from the operating room with the results. The spleen is removed (splenectomy) if that is the only site found. If, however, HSA has already spread to other tissues, the prognosis is grave and a decision is made to proceed with the splenectomy to preclude bleeding or to perform humane euthanasia at that time.
In the event that the tumor has ruptured and is bleeding, the dogs become very weak, breathe rapidly, have pale gums, and are in a critical situation. Not every splenic tumor that bleeds is HSA – so immediate surgery is indicated to assess the spleen, liver, and other abdominal organs and lymph nodes to correct the bleeding and assess the degree of tumor spread.
Benign massesmand some less aggressive tumors of the spleen afford a very favorable prognosis, but the life expectancy for patients with splenic HSA is poor despite aggressive surgical and drug therapy. Median survival time for splenic HSA treated with surgery alone is only a matter of days to about three months. The addition of chemotherapy following surgery has been reported to increase the median survival time to 140 days to over a year. The addition of immunotherapy (L-MTP – a drug the FDA has not approved) available only from other countries – reportedly increased survival to a median of 273 days in one study.
Alert pet owners that notice changes in their dog’s behavior and habits, and veterinarians that are able to make accurate diagnoses are keys to early detection and corrective action for these patients. The prominent signs are a decrease in activity levels and appetite, increased thirst, and weakness; be aware of these symptoms and please contact your veterinarian to have an examination done when noticed. Early detection and therapeutic action helps us to “get the bear”.

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