A retrospective study of visceral and nonvisceral hemangiosarcoma and hemangiomas in domestic animals.

Cases of hemangiosarcoma submitted to the Colorado State University Veterinary Diagnostic Laboratory during a 6-year period were reviewed. Visceral hemangiosarcomas represent less than 2% of canine specimens submitted for histologic examination and nonvisceral hemangiosarcoma less than 1%. Most nonvisceral hemangiosarcomas of dogs occur in skin. Hemangiosarcomas are less common in cats and usually occur in skin. They are also rare in other animal species. Animals with nonvisceral hemangiosarcomas are usually mature; dogs and cats average 10 years of age. The tumors develop in many different locations, and there is no sex predilection. A wide variety of dog breeds are affected, but Italian greyhounds, greyhounds, and whippets are overrepresented. Clinical outcomes of 76 cases of nonvisceral hemangiosarcomas in dogs and cats were obtained from submitting veterinarians. Completeness of excision of a tumor is the most important factor that can be used in predicting clinical outcome for an affected dog or cat. In all cases in which the animals were clinically normal for at least 1 year after surgical removal of a nonvisceral hemangiosarcoma, the margins were reported to be free of neoplastic cells. Degree of differentiation, mitotic rate, size of tumor, and presence or absence of epidermal ulceration, mast cells, or solar elastosis did not correlate with clinical outcome.