Angiosarcoma of breast, light micrograph. Angiosarcomas of the breast may be primary or occur following surgical and/or radiation treatment for breast cancer. It accounts for less than 0.1% of all primary malignancies of the breast. It appears as ill-defined, deep-seated, spongy, haemorrhagic lesion in the breast parenchyma. The image shows low-grade (Grade 1) primary angiosarcoma of the breast in a middle-aged female. It consists of well-defined, irregularly-shaped, anastomosing vascular channels lined by minimally atypical flattened endothelium. The vascular channels diffusely infiltrate the breast parenchyma and surround ducts (as seen here) and lobular units.