Disseminated hemangiosarcoma in the horse: 35 cases

Thirty-five cases of disseminated hemangiosarcoma (21 clinical cases and 14 previously reported cases) were reviewed to describe the disease in horses . Hemangiosarcoma occurred in mature, particularly middle-aged horses, with no apparent sex predilection. Thoroughbreds seemed to be overrepresented ( 13 cases) but a true breed predilection could not be established. The respi ratory and musculoskeletal systems were most commonly affected and presenti ng complaints included dyspnea (26%). subcutaneous or muscular swelling (24 %), epistaxis (17%), and lameness (12%). Heart and respiratory rates were u sually increased and mucous membrane color was frequently pale or icteric. Capillary refill rime and rectal temperature were often normal. Anemia (88% ), neutrophilic leukocytosis (62%), and thrombocytopenia (48%) were common. Examination of tissue samples collected by fine-needle aspirate or biopsy established an antemortem diagnosis in 4 horses. The diagnosis was made dur ing postmortem examination in the remaining 31 horses. The lung and pleura (77%), skeletal muscle (46%), and spleen (43%) were most commonly affected. A primary site of tumor involvement could be identified in 22 horses. Hema ngiosarcoma should be included as a differential diagnosis for horses with evidence of hemorrhage into body cavities, skeletal muscle, or subcutaneous locations.