Liposarcoma of the breast is a very rare malignant tumor. It can clinically manifest as a palpable breast mass and mimic primary breast cancer. We report an unusual case of a 51-year-old female who presented with an asymptomatic right breast mass, which was histologically diagnosed as well differentiated liposarcoma arisen within malignant phyllodes tumor. The patient underwent breast conserving surgery, received no adjuvant treatment and is disease-free after 2 years. Radiological and histopathological features are presented and described in detail. Data from the literature are presented and therapy recommendations discussed.