Current understanding of phyllodes tumors of the breast: Tumor classification, molecular landscape, and best pathology practice

Phyllodes tumors of the breast are uncommon biphasic fibroepithelial lesions comprised of neoplastic stromal cells and a nonneoplastic epithelial component. Unlike fibroadenomas, which are the most common benign breast neoplasms, phyllodes tumors can be benign, borderline, or malignant and can rarely metastasize. While the accurate diagnosis and classification of these lesions is therefore critical, both often prove challenging for pathologists. This review will provide an overview of phyllodes tumors including their epidemiology, clinical and radiologic presentations, macroscopic and microscopic features, classification and clinical behavior, immunohistochemical profile, differential diagnosis, and management. The review will conclude with a discussion of some of the evolving tools and technologies that may assist with the evaluation of phyllodes tumors in the future.