Immunocytochemical utility of claudin-4 versus those of Ber-EP4 and MOC-31 in effusion cytology.

Background: Recently, claudin-4 (CL4) immunocytochemistry was reported to be useful for differential diagnosis in effusion cytology. We wondered whether CL4 might be useful for "single-shot" identification of metastatic carcinoma. The purpose of this study was to evaluate the usefulness of CL4 in effusion cytology.

Methods: In total, 266 cases (169 metastatic carcinomas, eight malignant mesotheliomas, and 89 reactive mesothelial cells) were selected. Immunocytochemical examinations of cell-block sections were performed for CL4, Ber-EP4, and MOC-31. We used an arbitrary 4-tiered scale based on both staining intensity and positive-cell percentage among all target cells, and calculated a staining index score (sum of the above two scores).

Results: In a ROC-curve analysis, higher area-under-curve values were found for CL4 than for Ber-EP4 or MOC-31 (0.982, 0.942, and 0.926, respectively).

Conclusions: Since CL4 exhibited similar or superior usefulness to Ber-EP4 and MOC-31, it could become the first choice for the above differential diagnosis in effusion cytology. Diagn. Cytopathol. 2016;44:499-504. © 2016 Wiley Periodicals, Inc.