Dr. Ann Hohenhaus provides an excellent understanding of hemangiosarcoma in her article Pet Cancer: Understanding Hemangiosarcoma in Dogs and Cats.
Pet Cancer: Understanding Hemangiosarcoma in Dogs and Cats
Hemangiosarcoma strikes like a lightning bolt. One minute your pet is fine and the next, he has collapsed from internal bleeding. As an oncologist, I rarely see this tumor until after the emergency room has corrected the internal hemorrhage via surgery and the biopsy report comes back. Because hemangiosarcoma is not an uncommon tumor, especially for some popular breeds of dog, here are some facts you ought to know.
What Is Hemangiosarcoma?
Cancer is an uncontrolled proliferation of cells that have the potential to spread throughout the body. We often think of cancer as arising from various organs in the body: breast cancer, colon cancer, skin cancer. Hemangiosarcoma is a malignancy originating in an organ system we don’t think much about: the circulatory system, and specifically, blood vessels. The name of this tumor comes from the Greek word for blood vessel, hemangio, and sarcoma, the word for a malignancy derived from connective tissues like blood vessels.
Where Does It Occur?
Hemangiosarcoma arises from the highly specialized delivery system for blood. Since blood vessels are located all over the body, this cancer can – and does – develop everywhere. Despite the widespread nature of blood vessels, there are specific sites in the body where this cancer is most likely to occur: spleen, liver, heart and skin. Because hemangiosarcoma is a malignancy, meaning that it can invade and destroy nearby tissue and metastasize to other sites, this cancer can rapidly spread diffusely throughout the body – often before we can detect the presence of the tumor. For this reason, it is not one of my favorite tumors.
Who Is at Risk?
Both dogs and cats can suffer from hemangiosarcoma but the disease is far more common in dogs than in cats. Estimates suggest greater than 50,000 cases occur in dogs annually in the United States. Labrador Retrievers, Golden Retrievers, Boxers and German Shepherds are at higher risk for developing this malignancy.
What Are the Signs?
Pets with hemangiosarcoma may look deceptively normal until one of the cancerous blood vessels in the tumor ruptures. Then, in a heartbeat, your pet can go from looking normal to being in a state of collapse and shock. Blood can build up in the abdomen if the tumor arises from the spleen or liver and around the heart if the tumor arises from that organ. In either case, massive hemorrhage from the tumor’s abnormal blood vessels makes life-saving emergency surgery to remove the bleeding tumor a necessity in many cases.
How Can Hemangiosarcoma Be Detected?
Recognizing hemangiosarcoma before it spreads is a tall order. Hemangiosarcoma of the skin may look and feel like a fatty tumor (which is not malignant). Fine needle aspiration, a procedure in which a thin needle is used to draw fluid or cells from a lump or mass under the skin, may just reveal blood, but to me, this situation would put me on alert for a diagnosis of cutaneous hemangiosarcoma. Early detection of this tumor is nearly impossible when it occurs in an internal organ like the heart or spleen, because its signs are very subtle. Your pet’s annual physical examination, where your veterinarian does a nose-to-tail evaluation, may allow a splenic mass to be detected during abdominal palpation, but only if it is large enough to be detected in this way. Blood tests obtained at the annual check-up may reveal an unexplained anemia, but they also may be completely normal. Diagnostic imaging, such as X-rays and ultrasound, may also lead to the discovery of hemangiosarcoma.
How Is It Treated?
The first steps in treating hemangiosarcoma involve surgery to remove the bleeding tumor and a biopsy of the excised tissue to confirm the diagnosis. Once your pet has recovered from surgery, a consultation with a veterinary oncologist (cancer specialist) will help define the role of chemotherapy in your pet’s treatment. Chemotherapy is often recommended to slow the spread of cancer throughout the body. Surgery as the sole treatment results in about a 3-month average survival; the addition of chemotherapy can double that expected survival time for many dogs with splenic hemangiosarcoma, the most common location for the tumor. Unfortunately, due to its subtle nature, hemangiosarcoma is sometimes detected so late that treatment options can be very limited.
Why Isn’t the Prognosis Better?
Current investigation into the DNA abnormalities underlying hemangiosarcoma indicates that this tumor has cells that are more resistant to cancer treatments than the average cancer cell. Another line of research suggests that the immune system of certain breeds, like the Golden Retriever, has a decreased ability to recognize and clear cancer cells from the body, leading to the breed’s increased risk for hemangiosarcoma. These facts now give veterinary researchers targets for potential therapies and pet owners hope for new treatments in the future.