- Angiosarcomas are a rare but highly malignant tumors of endothelial cells.
- Cells can range widely in differentiation from those that look like typical endothelial cells forming recognizable vascular channels, similar to those found in hemangiomas, to highly anaplastic spindle-shaped cells that form solid sheets. Tumors may begin as small, demarcated, red nodules but eventually can transform into large, un-demarcated, soft masses.
- Angiosarcomas can occur in the skin or breast. Development in the liver is termed "Hepatic Angiosarcoma". Although Hepatic Angiosarcoma is extremely rare it is associated with exposure to a variety of specific carcinogens including polyvinyl chloride, arsenic, and thorotrast, a radiocontrast reagent.
- Local invasion and metastasis is common. Few patients survive beyond 5 years.