hemangiosarcoma

[hĭ-măn′jē-ō-sär-kōmə]
n.
  1. A rare malignant neoplasm characterized by rapidly proliferating anaplastic cells derived from blood vessels and lining blood-filled spaces.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.