title: Invasive Micropapillary Carcinoma of the Breast: An Update.
abstract: BACKGROUND
  -Invasive micropapillary carcinoma (IMPC) is a distinct variant of mammary carcinoma in which tumor cells are arranged in morulelike clusters devoid of fibrovascular cores and situated within empty stromal spaces. Identification of IMPC can be achieved by the assessment of morphologic features in conjunction with the characteristic "inside-out" staining pattern of epithelial membrane antigen and sialyl Lewis X highlighted by immunohistochemical analysis. Although recognizing micropapillary architecture is often not challenging, the criteria for distinguishing between mixed and pure IMPC remain imprecise. Some mucin-producing carcinomas can also have micropapillary histology, but there is no consensus on whether these tumors are variants of IMPC or mucinous carcinomas. The molecular genetic studies demonstrate that IMPCs have distinct molecular genetic profiles, supporting the theory that they constitute distinct pathologic entities. However, genomic analyses have not identified any specific genomic aberration that may explain the distinctive morphology and clinical behavior of IMPC.
  
  
  OBJECTIVE
  -To provide an overview on the current concepts in the diagnosis and pathogenesis of IMPC of the breast, incorporating recent molecular genetic advances and prognosis-based reclassification.
  
  
  METHODS
  -PubMed search and the cited references were reviewed.
  
  
  CONCLUSIONS
  -The recent evolution of prognosis-based reclassification and molecular genetic advances has enhanced our knowledge of the pathogenesis of IMPC of the breast. Additional studies might reveal consistent molecular alterations that underlie the formation of the inside-out growth pattern, and they might elucidate the molecular mechanisms responsible for the unfavorable clinical behavior of IMPC.
authors.forename: Yi-Ling
authors.initials: YL
authors.lastname: Yang
authors.forename: Bing-Bing
authors.initials: BB
authors.lastname: Liu
authors.forename: Xinmin
authors.initials: X
authors.lastname: Zhang
authors.affiliation: From the Department of Breast Pathology and Research Laboratory, Key Laboratory of Breast Cancer Prevention and Therapy, Ministry of Education, National Clinical Research Center for Cancer, Tianjin Medical University Cancer Institute and Hospital, Tianjin, China (Drs Yang, Liu, and Fu); and the Department of Pathology, Cooper University Hospital, Cooper Medical School of Rowan University, Camden, New Jersey (Dr Zhang). Drs Zhang and Fu jointly supervised the work.
authors.forename: Li
authors.initials: L
authors.lastname: Fu
mesh_terms: D001940:Breast / Q000378:metabolism / Q000473:pathology*; D001943:Breast Neoplasms / Q000175:diagnosis* / Q000235:genetics / Q000378:metabolism; D002291:Carcinoma, Papillary / Q000175:diagnosis* / Q000235:genetics / Q000378:metabolism; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007150:Immunohistochemistry; D035683:MicroRNAs / Q000235:genetics; D009361:Neoplasm Invasiveness; D009844:Oligosaccharides / Q000378:metabolism; D000080506:Sialyl Lewis X Antigen
chemical_list: D035683:MicroRNAs; D009844:Oligosaccharides; D000080506:Sialyl Lewis X Antigen