UCLA Radiological Sciences Proceedings

Malignant phyllodes tumors are rare fibroepithelial neoplasms, comprising less than 1% of all breast tumors. We report the case of a 46-year-old woman who presented with a rapidly enlarging right breast mass. Serial imaging revealed progressive growth from 1.1 cm to over 7 cm. Initial core biopsies suggested an atypical lipomatous neoplasm or well-differentiated liposarcoma. Features of phyllodes tumor were not seen. Multidisciplinary review recommended surgical excision. The patient underwent a skin-sparing mastectomy with wide margins. Final pathology confirmed a 7.1 cm malignant phyllodes tumor with high-grade liposarcoma. Postoperative management included post-mastectomy radiation due to close posterior margins. This case underscores the diagnostic challenges of lipomatous lesions occurring in phyllodes tumors, highlights the importance of clinicopathologic correlation, and demonstrates the critical role of multidisciplinary evaluation in managing rare and diagnostically challenging breast tumors.