Breast cancer. Light micrograph (LM) of a section of a breast angiosarcoma. Breast angiosarcomas are cancers that start in the cells that make up the walls of blood vessels or lymphatic vessels. Irregularly shaped vessels are lined by atypical endothelial cells. The intervening space is occupied by epithelioid tumor cells. Angiosarcoma are very rare and make up less than 1 in 100 breast cancers (less than 1 %). It is mostly seen in women, but men can also get this type of breast cancer. It carries a poor prognosis because of its high risk of local recurrence and distant metastases. Presently, there are still no established systemic therapies. Thus, the main treatment strategy for breast angiosarcoma is complete resection. Magnification: x 100 when printed at 10 centimetres wide. Human tissue.