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Papillary endothelial growth is usually a feature of intermediate-type (Grade II) and high-grade (Grade III) angiosarcomas of the breast. It ranges from small nests and tufts of endothelial cells protruding into the vascular lumen to complex branching and anastomosing papillary structures. When exuberant, endothelial tufting can create a nearly solid appearance. Cytologic atypia is mild to moderate consisting of slightly enlarged hyperchromatic nuclei. Mitotic activity is not appreciably increased in papillary endothelial tufts.