title: Distinguishing medullary carcinoma of the breast from high-grade hormone receptor-negative invasive ductal carcinoma: an immunohistochemical approach.
abstract: OBJECTIVE
  Medullary carcinomas (MCs) represent a rare breast cancer subtype associated with a rather favourable prognosis compared with invasive ductal carcinomas (IDCs). Due to histopathological overlap, MCs are frequently misclassified as high-grade IDCs, potentially leading to overtreatment of MCs. Our aim was to establish novel diagnostic markers distinguishing MCs from hormone receptor-negative high-grade IDCs.
  
  
  RESULTS
  Sixty-one MCs and 133 hormone receptor-negative IDCs were analysed in a comparative immunohistochemical study. Applied markers included a comprehensive panel of cytokeratins (CKs), vimentin, smooth muscle actin (SMA), p63, p53, cell adhesion molecules [N-CAM (CD56), syndecan-1 (CD138), E-cadherin and P-cadherin] and development associated transcription factors (AP-2 alpha, AP-2 gamma). A significantly higher proportion of IDCs displayed increased expression of CK7, AP-2 alpha and HER2 in contrast to MCs (CK7: 91% of IDCs versus 77% of MCs; AP-2 alpha: 77% versus 57%; and HER2: 26% versus 7%, each P < 0.01). Vice versa, MCs were slightly more frequently positive for SMA and vimentin (P > 0.05).
  
  
  CONCLUSIONS
  Hormone receptor-negative high-grade IDCs are significantly associated with luminal differentiation, Her2 and AP-2 alpha overexpression, whereas MCs tend to display myoepithelial features. Markers analysed in this study are of diagnostic value regarding the differential diagnosis of MCs.
authors.affiliation: Institute of Pathology, University Hospital Bonn, Bonn, Germany.
authors.forename: Uta
authors.initials: U
authors.lastname: Flucke
authors.forename: Maria Theresia
authors.initials: MT
authors.lastname: Flucke
authors.forename: Ludwig
authors.initials: L
authors.lastname: Hoy
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Breuer
authors.forename: Rolf
authors.initials: R
authors.lastname: Goebbels
authors.forename: Kerstin
authors.initials: K
authors.lastname: Rhiem
authors.forename: Rita
authors.initials: R
authors.lastname: Schmutzler
authors.forename: Helene
authors.initials: H
authors.lastname: Winzenried
authors.forename: Michael
authors.initials: M
authors.lastname: Braun
authors.forename: Susanne
authors.initials: S
authors.lastname: Steiner
authors.forename: Reinhard
authors.initials: R
authors.lastname: Buettner
authors.forename: Heidrun
authors.initials: H
authors.lastname: Gevensleben
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000378:metabolism; D001943:Breast Neoplasms / Q000378:metabolism / Q000473:pathology*; D018270:Carcinoma, Ductal, Breast / Q000378:metabolism / Q000473:pathology*; D018276:Carcinoma, Medullary / Q000378:metabolism / Q000473:pathology*; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008875:Middle Aged; D011379:Prognosis
chemical_list: D014408:Biomarkers, Tumor