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Basics ⬇

Outline

BASICS

Definition!!navigator!!

  • A malignant neoplasm originating from vascular endothelial cells.
  • May occur as a single mass, with or without local invasion, or disseminated through multiple organs

Pathophysiology!!navigator!!

Malignant transformation of endothelial cells.

Systems Affected!!navigator!!

All

Genetics!!navigator!!

No breed predilection identified.

Incidence/Prevalence!!navigator!!

Rare

Geographic Distribution!!navigator!!

Worldwide

Signalment!!navigator!!

  • Disseminated—more common in middle-aged horses (age range 3–26 years; mean 12 years).
  • Juvenile hemangiosarcoma seen in horses ≤3 years of age.
  • Congenital hemangiosarcoma has been reported

Signs!!navigator!!

  • Vary depending on location and often attributable to hemorrhage or mass effect/swelling.
  • Predominantly referable to respiratory and musculoskeletal systems including dyspnea, tachypnea (hemothorax), epistaxis, cough, subcutaneous edema/swelling, lameness, tachycardia, and pale/icteric mucous membranes.
  • Cutaneous form includes generally solitary dermal or subcutaneous lesions that are poorly circumscribed with necrosis, ulceration, or bleeding

Causes!!navigator!!

Unknown

Risk Factors!!navigator!!

Unknown

Diagnosis ⬆ ⬇

Outline

DIAGNOSIS

Differential Diagnosis!!navigator!!

  • Hemangiomas—benign endothelial cell tumors, generally in horses <1 year old.
  • With dyspnea—consider infectious or obstructive respiratory.
  • With epistaxis—consider trauma, infection including guttural pouch mycosis, neoplasia, coagulopathy, and exercise-induced pulmonary hemorrhage.
  • With lameness and/or muscular swelling—consider multiple causes including trauma (hematoma) and degenerative conditions, abscessation, or other forms of neoplasia

CBC/Biochemistry/Urinalysis!!navigator!!

  • Most common finding is anemia.
  • Neutrophilic leukocytosis and thrombocytopenia are common.
  • Variable total protein—hypoproteinemia accompanied by hypoalbuminemia is common.
  • Elevated globulin fractions (>4.0 g/dL) with normal to slightly elevated fibrinogen.
  • Biochemical abnormalities are nonspecific and may include mild to moderate azotemia and hyperbilirubinemia, increases in muscle enzyme activities, and mild electrolyte abnormalities

Other Laboratory Tests!!navigator!!

Immunohistochemistry using factor VIII-related antigen (von Willebrand factor) has been successfully used to identify endothelial cell origin cutaneous tumors.

Imaging!!navigator!!

May be useful (endoscopy, radiography, ultrasonography, and pleuroscopy) but typically lack specificity.

Other Diagnostic Procedures!!navigator!!

  • Antemortem diagnosis is difficult without direct visualization and biopsy.
  • Cytologic evaluation of various biologic fluids is often consistent with hemorrhage or inflammation and not specifically diagnostic.
  • Localization of signs to a specific system may allow for endoscopically guided biopsy.
  • Biopsy or fine needle aspiration may be diagnostic. Both histopathology (endothelial cells with numerous mitotic figures) and immunohistochemistry are helpful in differentiating hemangiosarcoma from hemorrhage and inflammation.
  • Diagnosis often established during postmortem examination

Pathologic Findings!!navigator!!

  • Common primary sites for disseminated hemangiosarcoma include lung, pleura, skeletal muscle, heart, and spleen.
  • Postmortem findings commonly include severe hemothorax and hemoabdomen, and hemorrhage within affected muscle groups. Tumors are friable, dark red to black masses within the affected organ or tissue.
  • Histologically, tumors consist of multiple, poorly organized vascular channels lined by plump, spindle-shaped cells. Neoplastic endothelial cells have large, ovoid, vesicular hyperchromic nuclei and prominent nucleoli with multiple, bizarre mitotic figures

Treatment ⬆ ⬇

Outline

TREATMENT

Appropriate Health Care!!navigator!!

N/A

Nursing Care!!navigator!!

General supportive care.

Activity!!navigator!!

N/A

Diet!!navigator!!

Horses with disseminated disease likely have poor appetite, so encouraging the horse to eat is important.

Client Education!!navigator!!

Warn owners of rapid deterioration in the disseminated form, and possibility of metastases if the localized mass is excised.

Surgical Considerations!!navigator!!

Surgical excision may be beneficial for cutaneous or well-localized lesions.

Medications ⬆ ⬇

MEDICATIONS

Drug(s) of Choice

No established protocols.

Follow-up ⬆ ⬇

Outline

FOLLOW-UP

Patient Monitoring!!navigator!!

Horses should be carefully monitored for recurrence/metastases following surgical excision.

Prevention/Avoidance!!navigator!!

N/A

Possible Complications!!navigator!!

Severe hemorrhage following biopsy.

Expected Course and Prognosis!!navigator!!

Clinical deterioration typically rapid with the disseminated form and the long-term prognosis is poor. Surgical excision has resulted in resolution in a small number of reported cases.

Miscellaneous ⬆ ⬇

Outline

MISCELLANEOUS

Associated Conditions!!navigator!!

N/A

Age-Related Factors!!navigator!!

N/A

Zoonotic Potential!!navigator!!

N/A

Pregnancy/Fertility/Breeding!!navigator!!

N/A

Synonyms!!navigator!!

  • Angiosarcoma.
  • Malignant hemangioendothelioma

See Also!!navigator!!

N/A

Suggested Reading ⬆ ⬇

Johns I, Stephen JO, Del Piero F, et al. Hemangiosarcoma in 11 young horses. J Vet Intern Med 2005;19:564–570.

Taintor J. Haemangiosarcoma in the horse. Equine Vet Educ 2014;26:499–503.

Author(s) ⬆

Author: Imogen Johns

Consulting Editors: David Hodgson, Harold C. McKenzie, and Jennifer L. Hodgson

Acknowledgment: The author and editors acknowledge the prior contribution of Mark V. Crisman.