Visceral hemangiosarcoma

What it is

Hemangiosarcoma is a malignant neoplasm of the vascular endothelium. The tumour forms blood-filled, fragile cavities that rupture easily and bleed. In the dog the visceral form is far more common and aggressive than the cutaneous form. The spleen is the most common primary site, followed by the right atrium, liver and other organs; spleen and right atrium can be involved at the same time. Metastasis by the bloodstream and implantation in the abdomen after rupture are early, so most dogs have micrometastatic disease when diagnosed.

Who it affects

Middle-aged to older dogs of large breeds: German shepherd, golden retriever, Labrador retriever and others. Not every splenic mass is hemangiosarcoma: haematomas and nodular hyperplasia are also common, and the distinction requires histopathology.

Anatomy involved

• Spleen: single or multiple cavitated masses that may rupture and cause haemoabdomen.
• Heart: masses in the wall of the right atrium and auricle; their rupture causes haemorrhagic pericardial effusion and cardiac tamponade.
• Liver: primary or, more often, metastatic nodules.
• Lungs: a frequent site of metastasis, with a miliary or nodular pattern.

Clinical signs

Often acute collapse from internal haemorrhage: weakness, pale mucous membranes, tachycardia, weak pulses and abdominal distension from haemoabdomen. Episodes may be intermittent, with spontaneous recovery as bleeding stops. Cardiac tumours present with signs of tamponade: muffled heart sounds, jugular distension, weak pulses, ascites and collapse. Ventricular arrhythmias are common.

Diagnosis

• Abdominal ultrasound: cavitated mixed-echogenicity splenic or hepatic mass and free fluid.
• Echocardiography: right atrial or auricular mass and pericardial effusion; best performed while effusion is present.
• Abdominocentesis or pericardiocentesis: haemorrhagic fluid; cytology of effusions is rarely diagnostic.
• Blood work: anaemia, schistocytes and acanthocytes, thrombocytopenia and coagulation changes compatible with disseminated intravascular coagulation.
• Staging: thoracic radiographs or CT and abdominal and cardiac imaging.
• Histopathology of the removed mass confirms the diagnosis.

Treatment

Splenic tumours are treated by splenectomy, after stabilisation with fluids and blood products. Cardiac tamponade is relieved by pericardiocentesis; resection of an auricular mass or pericardiectomy can be done in selected cases. Adjuvant doxorubicin-based chemotherapy modestly prolongs survival. Even with surgery and chemotherapy the prognosis is poor, with median survival measured in months.