Diagnostic Usefulness of MUC1 and MUC4 for Distinguishing between Metastatic Adenocarcinoma Cells and Reactive Mesothelial Cells in Effusion Cell Blocks

Objective: The aim of our study was to determine the diagnostic value of MUC1 and MUC4 for distinguishing between metastatic adenocarcinoma cells (MAC) and reactive mesothelial cells (RMC) in effusion fluids. Study Design: A total of 237 cell block specimens from pleural and peritoneal effusions, including 196 malignant effusions with MAC and 41 benign effusions with RMC, were stained with antibodies against MUC1 and MUC4. Membranous staining with or without cytoplasmic staining was considered to be positive. Results: MUC1 immunoreactivity was observed in 194 (99.0%) of 196 cases of MAC and in 20(48.8%) of 41 cases of RMC. MUC4 immunoreactivity was observed in 174 (88.8%) of 196 cases of MAC and in 4 (9.8%) of 41 cases of RMC. For distinguishing MAC from RMC, the MUC1 reactivity was found to be 99.0% sensitive and 51.2% specific with a positive predictive value of 90.7% and a negative predictive value of 91.3%. The sensitivity of MUC4 for MAC was 88.8%, the specificity was 90.2%, the negative predictive value was 62.7%, and the positive predictive value was 97.8%. Conclusion: Our data suggest that MUC4 appears to be a sensitive and specific marker for differentiating between MAC and RMC. Copyright (C) 2013 S. Karger AG, Basel