Radiation induced angiosarcoma of the breast is a form of malignant breast cancer that develops after radiation exposure, particularly radiation used to treat a prior breast cancer. This condition is rare and can develop years after exposure to radiation. Some symptoms include: changes in breast skin, enlarged breast, breast ulceration (sores and breaks in the breast's skin), and appearance of reddish-purple patches or palpable (able to be touched or felt) tumors. Radiation induced angiosarcoma of the breast occurs in roughly 0.5% of patients who underwent radiation and breast-conserving therapy for breast cancer. Treatment usually involves surgery, radiation therapy, or chemotherapy.