title: Claudins in differential diagnosis between mesothelioma and metastatic adenocarcinoma of the pleura.
abstract: OBJECTIVE
  To study the expression of claudins in mesothelioma and metastatic pleural adenocarcinoma.
  
  
  METHODS
  Immunohistochemical staining of claudins 1, 2, 3, 4, 5, and 7 was studied in 35 malignant mesotheliomas and the expression compared with 24 cases of pleural metastatic adenocarcinoma. All cases were also immunostained with calretinin.
  
  
  RESULTS
  Claudin 1, 2, 3, 4, 5, and 7 expression was seen in 40%, 80%, 18%, 23%, 14%, and 43% of mesotheliomas, respectively, while the corresponding figures for adenocarcinoma were 100%, 88%, 90%, 100%, 50%, and 92%. Claudins 1, 3, 4, 5, and 7 were significantly less positive in mesothelioma than in metastatic adenocarcinoma, while no difference was observed for claudin 2. Claudins 1, 3, 4, 5, and 7 were also inversely associated with calretinin positivity. Sarcomatoid and biphasic mesothelioma subtypes appeared more negative for these claudins than pure epithelioid subtypes. Claudin expression was not associated with survival of patients with malignant mesotheliomas.
  
  
  CONCLUSIONS
  The results show that malignant mesotheliomas have a lower expression of claudins 1, 3, 4, 5, and 7 than adenocarcinomas, and their expression could thus be used as an adjunct in differential diagnosis between the two. The difference was most evident for claudins 3 and 4, which were nearly as good as calretinin in mesothelioma detection. Sarcomatoid and biphasic mesotheliomas showed expression of these claudins only occasionally, which could be due to or contribute to their less epithelial appearance.
authors.affiliation: Department of Pathology, University of Oulu and Oulu University Hospital, Finland. ylermi.soini@ppshp.fi
authors.forename: Y
authors.initials: Y
authors.lastname: Soini
authors.forename: V
authors.initials: V
authors.lastname: Kinnula
authors.forename: K
authors.initials: K
authors.lastname: Kahlos
authors.forename: P
authors.initials: P
authors.lastname: Pääkkö
mesh_terms: D000230:Adenocarcinoma / Q000737:chemistry / Q000473:pathology / Q000556:secondary*; D014408:Biomarkers, Tumor / Q000032:analysis*; D064032:Calbindin 2; D062445:Claudin-1; D062465:Claudin-3; D062506:Claudin-4; D062507:Claudin-5; D057167:Claudins; D003937:Diagnosis, Differential; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D008297:Male; D008565:Membrane Proteins / Q000032:analysis*; D008654:Mesothelioma / Q000737:chemistry / Q000473:pathology*; D010997:Pleural Neoplasms / Q000737:chemistry / Q000473:pathology*; D011336:Probability; D064030:S100 Calcium Binding Protein G / Q000032:analysis; D015996:Survival Rate
chemical_list: D014408:Biomarkers, Tumor; C576764:CALB2 protein, human; C568108:CLDN1 protein, human; C491875:CLDN2 protein, human; C568122:CLDN3 protein, human; C568157:CLDN4 protein, human; C107466:CLDN5 protein, human; C473255:CLDN7 protein, human; D064032:Calbindin 2; D062445:Claudin-1; D062465:Claudin-3; D062506:Claudin-4; D062507:Claudin-5; D057167:Claudins; D008565:Membrane Proteins; D064030:S100 Calcium Binding Protein G