Hemangiosarcoma (malignant hemangiothelioma, angiosarcoma) is a malignancy of the vascular endothelial cells. The dog is the most frequently affected species. The hemangiosarcoma (HSA) is observed in 0.3 to 2% of all canine necropsies and constitutes about 5% of all malignancies in dogs. Adult dogs (range 8-13 years old) and German shepherd are most frequently affected. Other breeds with high incidence are Golden retriever, Labrador, Boxer, Schnauzer, and Pointer. Cutaneous HSA are overepresented in whippets, Pit bulls, Boxer and Dalmatians. Sex predisposition is not clear.

In dogs, the most common primary sites of HSA are the spleen, right atrium, subcutaneous tissue and liver. However, because this tumor originates from vascular endothelial cells, it can arise from anywhere in the body: bone, bladder, aorta, prostate, muscle, lungs, oral cavity, kidneys and uterus.

The biological behavior of hemangiosarcoma is highly malignant, with both local infiltration and metastases occurring early in the course of the disease. The only exception is the dermal HSA. Metastasis occur to lungs, liver, brain (it is the sarcoma that most often metastasizes to the brain), skin, bone and adrenal glands. Around 80% of the dogs can have metastasis by the time of diagnosis. Up to 25% of dogs with primary splenic HSA have concurrent cardiac involvement, and up to 63% of dogs with right atrial HSA have concurrent metastatic disease.

Clinical signs depend on the tumor size, localization, presence of metastasis, associated coagulopathies (DIC or local consumption) or rupture of the tumor. Patients may have nonspecific signs such as lethargy, anorexia and weight loss or more specific problems such acute dyspnea, pallor, abdominal effusion, or hypovolemic shock secondary to tumor rupture and hemorrhage. The most common physical abnormalities include palpable abdominal mass, intraabdominal fluid wave, arrhythmias, cardiac murmur, muffled heart sounds, venous congestion and signs compatible with cardiac tamponade.

Diagnosis is made by histopathology. However, breed, clinical signs at presentation, CBC, chemistry and coagulation profile findings may suggest HSA. A thorough staging evaluation is essential for accurate treatment recommendations and prognosis. Staging consists of CBC, chemistry and coagulation profile, urinalysis, thoracic radiographs, echocardiogram, electrocardiography and abdominal ultrasound. Findings of increased nucleated RBC, polychromasia, schistocytes, acanthocytes and thrombocytopenia on the CBC strongly suggest HSA.

The current standard of care for HSA is surgical resection of gross disease and adjuvant chemotherapy (table 1).

Table 1. Survival times in dogs with HSA and different treatments.

Many studies evaluating the results of chemotherapy have been published. Over the past years, recommendations on medical treatment have shifted from combination chemotherapy to single-agent chemotherapy, because the former had no strong survival advantage compared to doxorubicin therapy alone (table 1).

Other treatment strategies such as antiangiogenic therapy or more specific tumor targets are under investigation. However, the prognosis for dogs with HSA is still guarded. Early diagnosis and aggressive surgical and adjuvant chemotherapy seems to be the best strategy to provide a prolonged survival time and enhance the quality of life of patients with HSA.

References

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