+ Biologic Behavior
- HSA is a malignant neoplasm that arises from the endothelial cells
- HSA account for 4% of all primary bone tumors
- HSA should be differentiated from telangiectatic OSA
- breed predisposition: GSD ± Boxers and Great Danes
- sex predisposition: males
- 43% HSA occur in the appendicular skeleton and 57% in the axial skeleton
- sites: proximal humerus (most common), femur, ribs, vertebrae and scapula
- multiple lesions are relatively common
- soft tissue mass accompanies bony lesion in 50% of cases
- pathologic fracture is common
- = > 88% metastatic rate with metastatic disease developing < 6 months
- metastatic sites include lungs, liver, spleen, heart, skeletal muscle, kidney, brain, and other long bones
+ Treatment
- Survey radiographs: osteolytic with intramedullary extension and minimal cortical or periosteal changes
- Ultrasonographic examination of the heart and abdominal cavity is recommended for primary lesions
- Pulmonary metastatic disease is difficult to confirm as diffuse interstitial pattern mimics old age changes
- 12-month survival rate < 10% even with single bone lesions