Hemangiosarcoma in Dogs

By: Suzanne Brown, DVM

TVMA Member
Belton, TX

Published January 2016

Hemangiosarcoma refers to a cancer of the blood vessels. It is a very common cancer of large-breed dogs but can occur in other size dogs too. Until a pathologist examines the entire tumor or a biopsy sample, it is impossible to distinguish hemangiosarcomas from hemangiomas or hematomas, which are benign accumulations of blood vessels and can be cured with surgery.

Hemangiosarcomas are cancers of the blood vessels that are malignant, capable of spreading from the primary site to other locations in the body. The initial treatment for hemangiosarcoma is surgery. Surgery is aimed at removing the entire tumor and allows for a definitive diagnosis when a pathologist evaluates the tumor. Unfortunately, most hemangiosarcomas will return once removed, but treatment with a regimen of several medications (chemotherapy) may help extend the time before that occurs.

The initial diagnosis of hemangiosarcoma occurs in several ways. The clinical signs will depend on the location of the tumor. Although these masses can occur anywhere in the body, they occur most commonly in one of several locations discussed below.

Spleen:

Tumors on the spleen may become very large, up to the size of a basketball in some cases. These tumors are sometimes found during a routine veterinary exam, as your veterinarian palpates, or feels, on your dog’s abdomen. Other times they may be found on an X-ray or ultrasound of your pet’s abdomen.

Since these tumors are composed of blood vessels, there is a lot of blood within them. At times, sections of the tumor will rupture, causing the tumor to bleed into your pet’s abdomen. Although this is often painless when it occurs, if your pet loses large quantities of blood into its abdomen, your pet will look pot-bellied and feel very weak or tired.

Sometimes these ruptures cause the dog to lose so much blood the pet passes away in a short time. Other times, the pet may make it to a veterinarian’s office in time to have surgery to have the spleen removed. On some occasions, the bleeding stops on its own, and the pet may have a period of time where it feels tired but then recovers until the next episode. A surgery to remove the spleen, a splenectomy, can be done to remove the tumor as well as the entire spleen.

Liver:

The appearance of the tumor is much the same as when the tumor occurs in the spleen, and the symptoms are similar. The difference is tumors in the liver are much harder to remove. Some veterinarians are comfortable removing some portions of the liver; however, it is not always possible to remove the tumor, and many veterinarians are not comfortable doing surgery on the liver. The liver is a common site for metastasis (spread from another site), so your veterinarian will want to examine the rest of your pet’s body for other tumors if hemangiosarcoma is found on your pet’s liver.

Heart:

Hemangiosarcoma has a predilection for the right side of the heart. When the tumor occurs there, it has a tendency to cause bleeding into the sac around the heart (pericardium). If there is enough blood in the sac, the heart can’t pump blood effectively, and the dog begins to experience weakness, collapse or occasionally fluid build-up in the abdomen. Tumors in the heart can occasionally be removed surgically, but most often, if the tumors are discovered at that location, treatment is aimed at alleviating the associated clinical signs. This nonsurgical procedure, a pericardiocentesis, will remove the blood from the sac around the heart.

Skin:

Hemangiosarcomas of the skin have the best prognosis. These tumors tend to be flat with a red or purple-tinge, often occurring in areas with little to no fur. When removed promptly and with wide margins around them, they may sometimes be cured. They can be associated with excess sun exposure, so some animals may get multiple skin hemangiosarcomas.

Other hemangiosarcomas of the skin occur in the deeper (subcutaneous) tissues of the skin. These tumors have a higher likelihood of spreading to other sites and may be harder to remove. Staging of the disease (looking for other areas of the same disease) is important to make sure lesions on the skin are not indicative of a larger primary tumor elsewhere in the body.

Treatment:

If it is possible to remove the tumor, initial treatment of hemangiosarcoma always involves surgery. Prior to conducting the surgery, your veterinarian may want to examine the rest of your pet’s body for evidence of other tumors. If the tumor has already spread, the pet’s prognosis is poor. Searching for sites of tumor spread often involves a full physical exam, X-rays of the chest and an ultrasound of your pet’s abdomen and heart.

After surgery, some chemotherapy medications can help slow the recurrence of the disease.

Prognosis:

With the exception of the skin form of the disease, a cure is not expected. The disease almost always returns; when it does, treatment is rarely effective. The prognosis for confirmed hemangiosarcoma in locations other than the skin is poor. Even with surgical removal and chemotherapy, most dogs can be expected to live five to eight months. If you are concerned your dog has signs of cancer of any type, please see your veterinarian so your pet may be appropriately evaluated and treated.

Suzanne Brown, DVM, is a graduate of Texas A&M College of Veterinary Medicine who lives in Belton, Texas. Dr. Brown practices at Belton Small Animal Clinic and Central Texas Mobile Veterinary Ultrasound.