title: Immunohistochemical features of claudin-low intrinsic subtype in metaplastic breast carcinomas.
abstract: OBJECTIVE
  The claudin-low molecular subtype of breast cancer includes triple negative invasive carcinomas, with a high frequency of metaplastic and medullary features. The aim of this study was to evaluate the immunohistochemistry expression of claudins in a series of metaplastic breast carcinomas. We also assessed other claudin-low features, such as the cancer stem cell-like and epithelial-to-mesenchymal transition phenotypes.
  
  
  RESULTS
  The majority of the cases showed weak or negative staining for membrane claudins expression. We found 76.9% (10/13) low expressing cases for claudin-1, 84.6% (11/13) for claudin-3 and claudin-4, and 92.3% (12/13) for claudin-7. Regarding the cancer stem cell marker ALDH1, 30.8% (4/13) showed positive staining. We also showed that the majority of the cases presented a CD44(+)CD24(-/low) phenotype, positivity for vimentin and lack of E-cadherin expression. Interestingly, these claudin-low molecular features were specific of the mesenchymal component of metaplastic breast carcinomas, since its frequency was very low in other breast cancer molecular subtypes, as luminal, HER2-overexpressing and non-metaplastic triple negative tumors.
  
  
  CONCLUSIONS
  The negative/low expression of claudins and E-cadherin, high levels of vimentin, and the breast cancer stem cell phenotype suggests that metaplastic breast carcinomas have similar features to the ones included in the claudin-low molecular subtype, specially their mesenchymal components.
authors.affiliation: IPATIMUP - Institute of Molecular Pathology and Immunology of Porto University, Porto, Portugal.
authors.forename: Renê
authors.initials: R
authors.lastname: Gerhard
authors.forename: Sara
authors.initials: S
authors.lastname: Ricardo
authors.forename: André
authors.initials: A
authors.lastname: Albergaria
authors.forename: Madalena
authors.initials: M
authors.lastname: Gomes
authors.forename: Alfredo Ribeiro
authors.initials: AR
authors.lastname: Silva
authors.forename: Ângela Flavia
authors.initials: ÂF
authors.lastname: Logullo
authors.forename: Jorge F
authors.initials: JF
authors.lastname: Cameselle-Teijeiro
authors.forename: Joana
authors.initials: J
authors.lastname: Paredes
authors.forename: Fernando
authors.initials: F
authors.lastname: Schmitt
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D014408:Biomarkers, Tumor / Q000378:metabolism*; D001943:Breast Neoplasms / Q000378:metabolism* / Q000473:pathology*; D002277:Carcinoma / Q000378:metabolism* / Q000473:pathology*; D062445:Claudin-1; D062465:Claudin-3; D062506:Claudin-4; D057167:Claudins / Q000378:metabolism*; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008565:Membrane Proteins / Q000378:metabolism; D008679:Metaplasia / Q000378:metabolism / Q000473:pathology; D008875:Middle Aged; D055815:Young Adult
chemical_list: D014408:Biomarkers, Tumor; C568108:CLDN1 protein, human; C568122:CLDN3 protein, human; C568157:CLDN4 protein, human; C473255:CLDN7 protein, human; D062445:Claudin-1; D062465:Claudin-3; D062506:Claudin-4; D057167:Claudins; D008565:Membrane Proteins