We present the case of a 54 year old woman with RASB (poorly differentiated angiosarcoma of the left breast; pT1, pNX, M0, L0, V0) and a history of invasive-ductal cancer of the left breast (pT1b, G2, pN0, ER positive, PR positive, HER-2/neu negative) treated in July 2012 with breast-conserving surgery, adjuvant chemotherapy with 6 cycles of epirubicin and cyclophosphamide, adjuvant irradiation of the left breast with 50 Gray, and adjuvant endocrine therapy with an aromatase inhibitor. The gene discussed is ESR1; the disease is angiosarcoma.