Hemangiosarcoma:  A Malignancy of Cats and Dogs

Hemangiosarcoma, also known as malignant hemangiothelioma or angiosarcoma, is a malignant neoplasm that arises from vascular endothelial cells.  The canine is the most frequently affected species, but the incidence in cats appears to be rising.  As might be expected of a tumor originating in the blood system, they are highly malignant and can be found almost anywhere on the body.

  In canines, they occur predominantly in older males, with an average age of 8-10 years.  Breeds that are most frequently affected include the German shepherd and the Golden retriever.  The spleen, right atrium, and subcutis are the common sites of involvement.  In felines, they are usually solitary tumors with a predilection for the head (especially eyelids), ear tips, nasal planum, and non-pigmented skin.  Feline, as well as some canine, cutaneous hemangiosarcomas are similar to squamous cell carcinoma in that they can be actinic or sunlight-induced.  The etiology of hemangiosarcomas is unknown, but reports in human cases suggest a correlation between hemangiosarcomas and exposure to carbon dioxide, arsenicals, or vinyl chloride.

  In general, the biological behavior of this neoplasm is highly aggressive with most forms of the tumor metastasizing early in the disease process.  Visceral hemangiosarcomas are highly aggressive tumors with a poor prognosis.  Death is often associated with rupture of nodules or masses and resultant hemoabdomen or hemo-pericardium.  Cutaneous hemangio-sarcomas are less aggressive than their visceral counterparts with lower metastatic potential and longer survival times.

Clinical presentation and history: Clinical signs depend on the tumor size, location, presence of metastasis, and associated secondary complication (i.e., DIC or nodule rupture).  More than half of dogs with hemangiosarcoma are evaluated because of acute collapse after spontaneous rupture of the primary tumor or a metastatic lesion.  In addition, dogs with splenic hemangiosarcoma often are seen because of abdominal distension secondary to tumor growth or hemoabdomen.  Other common presenting signs include visible bleeding (typically epistaxis), exercise intolerance, episodes of weakness, pale mucous membranes, increased respiratory rate, and depression and lethargy.

  Dogs and cats with cutaneous or subcutaneous hemangiosarcoma are usually evaluated for a nodule that is generally a single, well-defined mass which is red/brown to black, soft to firm, and may exude blood when cut.  The blood disorder that commonly accompanies hemangiosarcoma is disseminated intravascular coagulopathy (DIC).  This process involves blood clotting that occurs inappropriately inside the blood vessels.  In DIC, blood clotting factors are consumed rapidly resulting in platelet deficiencies, increased clotting times, decreased fibrin content, and increased fibrin degradation products.  DIC can commonly be the cause of death in many cases of hemangiosarcoma.

Diagnosis:  Hemangiosarcomas can be diagnosed cytologically on the basis of the appearance of fine-needle aspirates or impression smears.  The neoplastic cells are similar to those in other sarcomas, as they are often spindle-shaped, but vary considerably in shape.  These spindyloid cells often have large nuclei with a lacey chromatin pattern, one or more nucleoli, blue-grey vacuolated cytoplasm, and an increase in mitotic figures.  Breed and clinical signs may also suggest a diagnosis of hemangiosarcoma.  Histo-pathology is confirmatory.

Clinical diagnostic points:

• CBC: mild to severe anemia, leukocytosis, thrombocytopenia
• Chemistry: increased hepatic enzymes
• Abdominal radiographs: Appearance of an intra-abdominal mass
• Thoracic radiographs: pulmonary nodules, right atrial enlargement
• Abdominal ultrasound: splenic mass, peritoneal effusion, hepatic nodules, enlarged mesenteric lymph nodes

Treatment and prognosis:  Surgical excision is the preferred choice of treatment for dermal or subcutaneous hemangiosarcomas.  Various chemo-therapeutic regimes have been attempted on dogs with multicentric visceral with little success.  Survival times vary with the location and stage of the tumor but, in general (with exception of dermal hemangiosarcomas), are quite short.  Studies have shown survival times of 20-60 days following detection of the tumor, with a one year survival rate in less than 10% of patients.

-by Salvador Galindo, ECFVG Student

-edited by Dr. Angela Smith, ADDL   Graduate Student

References

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4. Merlo M: 2002.  Primary right atrium haemangiosarcoma in a cat.  J Feline Med and Surg 4: 61-64.

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