angiosarcoma

A rare malignant neoplasm occurring most often in soft tissues, and believed to originate from the endothelial cells of blood vessel s; microscopically composed of spindle-shaped cells, some of which line small spaces resembling vascular clefts.

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an·gio·sar·co·ma .an-jē-ō-sär-'kō-mə n, pl -mas also -ma·ta -mət-ə a rare malignant vascular tumor (as of the liver or breast)

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an·gio·sar·co·ma (an″je-o-sahr-koґmə) [angio- + sarcoma] a malignant neoplasm arising from vascular endothelial cells; the term may be used generally or may denote a specific histologic subtype, usually hemangiosarcoma but sometimes lymphangiosarcoma or hemangiopericytoma.