title: Fibroepithelial tumors of the breast: pathologic and immunohistochemical features and molecular mechanisms.
abstract: BACKGROUND
  The 2 main prototypes of fibroepithelial tumors of the breast include fibroadenoma and phyllodes tumor (PT). Although both tumors share some overlapping histologic features, there are significant differences in their clinical behavior and management. Phyllodes tumors have been further divided into clinically relevant subtypes, and there is more than one classification scheme for PT currently in use, suggesting a lack of consistency within different practices. Accurate differentiation between fibroadenoma and PT, as well as the grading of PT, may sometimes be challenging on preoperative core needle biopsy. Some immunohistochemical markers have been suggested to aid in the pathologic classification of these lesions.
  
  
  OBJECTIVE
  To discuss the salient histopathologic features of fibroepithelial tumors and review the molecular pathways proposed for the initiation, progression, and metastasis of PTs. Also, to provide an update on immunohistochemical markers that may be useful in their differential diagnosis and outline the practice and experience at our institution from a pathologic perspective.
  
  
  METHODS
  Sources included published articles from peer-reviewed journals in PubMed (US National Library of Medicine).
  
  
  CONCLUSIONS
  Fibroepithelial tumor of the breast is a heterogenous group of lesions ranging from fibroadenoma at the benign end of the spectrum to malignant PT. There are overlapping histologic features among various subtypes, and transformation and progression to a more malignant phenotype may also occur. Given the significant clinical differences within various subtypes, accurate pathologic classification is important for appropriate management. Although some immunohistochemical markers may be useful in this differential diagnosis, histomorphology still remains the gold standard.
authors.affiliation: From the Department of Pathology, University of Massachusetts Medical School and UMass Memorial Medical Center, Worcester.
authors.forename: Xiaofang
authors.initials: X
authors.lastname: Yang
authors.forename: Dina
authors.initials: D
authors.lastname: Kandil
authors.forename: Ediz F
authors.initials: EF
authors.lastname: Cosar
authors.forename: Ashraf
authors.initials: A
authors.lastname: Khan
mesh_terms: D014408:Biomarkers, Tumor / Q000032:analysis*; D001943:Breast Neoplasms / Q000145:classification / Q000175:diagnosis* / Q000378:metabolism; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D018225:Neoplasms, Fibroepithelial / Q000145:classification / Q000175:diagnosis* / Q000378:metabolism
chemical_list: D014408:Biomarkers, Tumor