Intramuscular hemangiosarcoma in a horse

Abstract

Sugar Parkinson, a 15 year old Appendix Quarter Horse mare, presented to the Large Animal Emergency Service for a primary complaint of bilateral epistaxis. She had a history of intermittent epistaxis for the previous 5 days along with severe swelling of her neck and left hind limb. Anormalities on her initial exam included: depressed mentation, severe edema of her neck and left hind limb, icteric sclera, pale mucous membranes, and tachycardia. Preliminary blood work revealed moderate anemia (PCV of 22%) and severe thrombocytopenia (13 thou/ul). Endoscopy revealed marked ecchymoses of the nasopharynx mucosa and a presumed aneurism of the right internal carotid artery. Her problem list initially included: anemia, thrombocytopenia, icterus, previous bilateral epistaxis, and presumed aneurism of the right internal carotid artery. Her working diagnosis was primary or secondary immune-mediated thrombocytopenia and she was treated with immunosuppressive drugs and antibiotics for 5 days. Sonographic exam of the neck and leg revealed a mass in the cranial neck and a fine needle aspirate was taken. The aspirate revealed neoplastic cells indicating a soft tissue sarcoma with hemangiosarcoma considered most likely. Sugar was humanely euthanized. Hemangiosarcoma is an uncommon neoplasia in equines. Previous studies have shown no breed or sex predilection. There are two formed recognized: cutaneous/locally invasive, and disseminated. Both forms are more common in middle-age horses, with a range of 3-27 years. Clinical signs of the disseminated form typically involve the respiratory and musculoskeletal systems (dyspnea, epistaxis, edema, tachycardia). Antemortem diagnosis of the disseminated form is very difficult, unless a mass can be located and aspirated or biopsied. Prognosis is poor, though horses have been reported to live 4 years with the locally invasive forms. Treatment is speculative at this time, but options could include systemic doxorubicin or intralesional cisplatin treatment.