H: Hemangiosarcoma, Bone

Hemangiosarcoma, Bone

BASICS

OVERVIEW

A highly metastatic malignant tumor of the vascular endothelium.
Primary bone hemangiosarcoma is rare.
Accounts for < 5% of all bone tumors (appendicular site varies; axial site, rib is most common).
May be difficult to distinguish primary from metastatic lesions.
Immunohistochemistry needed to differentiate from telangiectatic osteosarcoma.

SIGNALMENT

SIGNS

Historical Findings

Appendicular—lameness; soft tissue swelling/mass at site; pathologic fracture.
Axial—for the rib a thoracic wall swelling; dyspnea if hemorrhagic pleural effusion is noted.

Physical Examination Findings

CAUSES & RISK FACTORS

Unknown

DIAGNOSIS

DIFFERENTIAL DIAGNOSIS

Other primary or metastatic bone tumors (osteosarcoma, telangiectatic OSA, fibrosarcoma, and chondrosarcoma).
Osteomyelitis (bacterial or fungal).

CBC/BIOCHEMISTRY/URINALYSIS

OTHER LABORATORY TESTS

Coagulation panel—may indicate DIC

IMAGING

Radiography of bone may reveal poorly marginated osteolytic lesion with minimal periosteal reaction; pathologic fractures possible.
Thoracic radiography to identify pulmonary metastasis.
Abdominal and cardiac ultrasonography to identify primary visceral tumor (spleen, liver, or cardiac) or metastasis.
CT scan can better define the extent of bone tumor for surgical excision (especially rib) and provides a more sensitive assessment for pulmonary metastasis.

DIAGNOSTIC PROCEDURES

An incisional biopsy may yield a diagnosis but due to the vascular nature of the tumor, blood contamination of specimen may preclude a diagnosis or prevent differentiation between HSA and telangiectatic OSA.
Excisional biopsy is the preferred method for diagnosis.

PATHOLOGIC FINDINGS

Gross evaluation reveals a dark, friable mass often within the medullary cavity of the bone.
Histopathology is characterized by anaplastic mesenchymal cells arranged in chords separated by a collagenous background for vascular channels and spaces filled with red blood cells, thrombi, and necrotic debris.

TREATMENT

Aggressive surgical excision of tumor sites.
- Amputation is required if appendicular.
- Axial tumors may be more difficult to remove.
Adjunctive chemotherapy is indicated due to high metastatic potential.
- Doxorubicin-based protocols (alone or in combination with vincristine and or cyclophosphamide).
Radiation therapy may be used for palliation of bone-related pain.

MEDICATIONS

DRUG(S)

Doxorubicin alone: 30 mg/m2 IV dogs > 10 kg; 1 mg/kg IV dogs < 10 kg q2 weeks × five cycles; cats 1 mg/kg IV q3 weeks.
Addition of cyclophosphamide and vincristine may be considered to dose intensify systemic therapy.

CONTRAINDICATIONS/POSSIBLE INTERACTIONS

In dogs, doxorubicin has a cumulative cardiotoxicity and is not recommended in animals with myocardial disease. Evaluate cardiac function with echocardiography prior to therapy in breeds predisposed to dilated cardiomyopathy.
For cats, doxorubicin can cause nephrotoxicity and renal values (urine specific gravity, BUN, creatinine) should be evaluated prior to therapy and every two to three cycles.

FOLLOW-UP

PATIENT MONITORING

Thoracic radiography, cardiac and abdominal ultrasound, and physical examination—1, 4, 7, 10, 13, 18, and 24 months after treatment.

POSSIBLE COMPLICATIONS

Pathologic fractures.
Tumors (rib) and metastatic lesions may rupture, resulting in clinical signs related to effusion or anemia.

EXPECTED COURSE AND PROGNOSIS

Overall median survival time is unknown due to rarity of cases.
Less than 10% of patients survive 1 year following surgery alone.
Median survival (all locations) after surgery and chemotherapy is unknown but likely similar to that seen with HSA of the spleen.

ABBREVIATIONS