Hemangiosarcoma (HSA) is a cancer that arises from malignant blood vessel cells and is an uncommon cancer in cats. It is a very aggressive cancer that spreads (metastasis) early and is associated with a poor prognosis. The underlying cause of HSA is unknown. HSA has the potential to affect any tissue in the body with the common primary sites being the spleen/internal organs or and skin or subcutaneous tissue. Cancer spread may occur early in the disease. The liver, abdominal lining tissue, and lung are the most common sites of metastasis. Metastasis may occur via the blood or local “seeding” of tumor cells after HSA rupture. Cutaneous HSA tends to have a lower metastatic rate, and it appears that the deeper the tumor, the greater the likelihood of metastasis.
The primary complaint and clinical signs in cats with HSA will vary and depend upon the location of the tumor and the presence or absence of tumor spread. Some cats may present with weakness or collapse from tumor rupture leading to internal hemorrhage. Alternatively, tumors may be identified during grooming, petting or routine physical examination. Diagnosis of HSA is based on biopsy and histopathology. Staging (looking for where the cancer is present in the body) for HSA includes bloodwork, radiographs, and abdominal ultrasound.
Treatment of HSA includes patient stabilization (in the case of acute tumor rupture and internal hemorrhage), surgery to remove the primary tumor and prevent further hemorrhage, and chemotherapy to prevent the growth of microscopic/metastatic cancer. Surgery by itself can be curative for superficial skin associated HSA but not for deeper tumors. Surgery alone for other types of HSA does little to prolong survival and most cats succumb to cancer spread within approximately 3 months. The addition of chemotherapy to treatment protocols has been shown to increase survival and most cats have an excellent quality of life. Most protocols involve the use of doxorubicin as the main chemotherapeutic. The survival times associated with these protocols are very similar and are generally 6-9 months, although there is very little statistical data available in cats.