Cancer of the blood vessel walls, called hemangiosarcoma, is most often seen in German Shepherds, Golden Retrievers, Flat-Coated Retrievers, and Boxers. This cancer can occur either inside the body cavity or on the surface of the skin. The skin variety can be easily removed surgically and carries an excellent chance of full recovery. Unfortunately, internal hemangiosarcoma is almost certainly fatal. Growths that form in the spleen, heart or liver are difficult to detect until they become large enough to show symptoms. Even at a microscopic level, hemangiosarcoma can spread and progress throughout the body, forming large, blood-filled tumors virtually anywhere. When one of these tumors bursts, it can cause an immediate internal bleeding crisis signified by sudden whitening of the gums, weakness and collapse.  Owners who notice any abnormalities of the skin, lumps in the abdomen, or abnormal weakness in their pet should see a veterinarian immediately.

Hemangiosarcoma is an aggressive cancer affecting the cells that make up blood vessels, often forming masses in the spleen or heart. The cancerous tissue forming these masses is not as strong as ordinary tissue and may rupture when filled with blood, causing sudden internal bleeding emergencies and potentially death.

Dermal hemangiosarcoma presents as a bluish, black or red lump in the skin. This condition may have a sun-exposure component, and occurs on areas with sparser hair growth. Dogs with short, white hair are at greatest risk for this type of hemangiosarcoma. A veterinarian will make a physical inspection of the lump and likely will send a sample for analysis.

When an older dog presents with internal bleeding, a ruptured splenic hemangiosarcoma is often suspected. If present, a splenectomy will be performed and the dog will be stabilised with fluids and possibly blood transfusions. Many animals will survive the incident. However, the tumour will often have already spread. Visceral hemangiosarcoma is sometimes only diagnosed post-mortem due to the sudden onset of symptoms from a ruptured tumor. However, if a tumor happens to be close to the skin and is successfully detected, there are a number of ways to identify the cancer. The veterinarian will look for general swelling of the abdomen, and will look at the dog’s gums to see if they are pale, a simple check for anemia. If the lump is not immediately identified as benign, a blood analysis, urine sample analysis, and medical imaging of the chest and abdomen will also be requested. A biopsy of the tumor may be taken, but this must be done carefully to avoid triggering an internal bleeding crisis.

In the case of dermal hemangiosarcoma, careful surgical removal is usually highly effective. If the tumor has been allowed to infiltrate the lower layers of the skin or muscle, chemotherapy is often administered as well and can include IV treatments of cyclophosphamide. Surgical excision and and chemotherapy combined give an excellent prognosis.

Visceral hemangiosarcoma treatment depends on the extent and size of the tumors. In cases where the cancer is localized to the spleen and has not ruptured, surgical removal along with chemotherapy can give a median survival time of around 4 months. Only 10% of dogs survive more than a year with visceral hemangiosarcoma. Complications of this cancer include clotting disorders leading to hemorrhage, intense pain if the cancer spreads to the bone, weakness and vomiting. In cases where the cancer has spread beyond the spleen, many veterinarians deem it kinder to euthanize the dog rather than subject it to the effects of the cancer.

Dermal hemangiosarcoma is survivable if the tumor is small, removed completely and follow-up chemotherapy administered. Cases where the tumor has spread carry a poor outlook of 6-10 months survival time. Follow-up appointments and imaging will be needed to make sure the cancer has not spread or relapsed.

Visceral hemangiosarcoma is almost always fatal in the long term. Pain can sometimes be managed with analgesics, but the severity of the cancer is such that recovery is not possible, and pets often succumb to the complications of living with it.