Diagnostic usefulness of claudin-4 for distinguishing between metastatic adenocarcinoma cells and reactive mesothelial cells in effusion cell blocks

Abstract

Although the exact roles of claudin-4 protein in tumorigenesis are still being uncovered, it is clear that it represents promising targets for cancer detection. The aim of our study was to determine the diagnostic value of claudin-4 for distinguishing between metastatic adenocarcinoma cells (MAC) and reactive mesothelial cells (RMC) in effusion fluids. A total of 234 cell block specimens from pleural and peritoneal effusions, including 194 malignant effusions with MAC and 40 benign effusions with RMC were stained with antibodies against claudin-4. Claudin-4 immunoreactivity was observed in 194 (100%) of 194 cases of MAC and in 11 (27.5%) of 40 cases of RMC. The area of positive staining for claudin-4 was >25% in 191 (98.5%) of 194 cases of MAC. In contrast, all claudin-4-positive RMC samples exhibited reactivity in