Angiosarcoma of the breast that arises in the absence of known risk factors, termed primary angiosarcoma, represents less than 1% of all primary breast malignancies and 3% to 10% of all breast sarcomas.1 In general, the disease is considered to be rare.2 It is more prevalent in younger populations and is most often found in women during their third to fourth decade of life. Secondary angiosarcoma of the breast is more common and is associated with known risk factors including extremity edema and chronic lymphedema. Angiosarcoma after a breast-conserving procedure is increasingly diagnosed in a small but significant portion of breast carcinoma survivors.3 Recently, multiple studies have established an association between radiation therapy and breast angiosarcoma. Cozen et al4 reviewed 264 444 cases of women in Los Angeles County, California, with previous invasive ductal carcinoma and found a significantly increased risk of angiosarcoma of the upper extremity (odds ratio = 59) and of the breast or chest wall (odds ratio = 11.6). This increased risk is thought to be related to persistent lymphedema or the radiation therapy itself. In a review5 of 194 798 cases of breast cancer from the Surveillance, Epidemiology, and End Results Program data, patients who had undergone breast conservation and radiotherapy had a relative risk of 15.9 of developing angiosarcoma. Lesions tend to appear 4 to 7 years after therapy and may be related to persistent lymphedema.