We experienced a leiomyosarcoma of the breast in an 18-year-old female. No specific treatment has been established. In order to clarify appropriate therapeutic management methods, the limited data available from our and previous case reports were assessed. A leiomyosarcoma of the breast must be excised with a negative margin. If the tumor size is large and an adequate margin, greater than 3-cm margin around the excised tumor, is not achieved due to anatomical constraints, radiotherapy may be indicated.