<p> <b><span style="font-size: 14pt; line-height: 200%; font-family: "Times New Roman", serif;">BACKGROUND- </span></b><span style="font-size: 14pt; line-height: 200%; font-family: "Times New Roman", serif;">Morphological distinction between metastatic carcinoma cells & reactive mesothelial cells is difficult in many occasions in effusion cytology. Immunohistochemistry plays important role in distinguishing the two.</span><span style="font-size: 14pt; line-height: 200%; font-family: "Times New Roman", serif; color: rgb(35, 31, 32);"> Immunohistochemistry for claudin-4,  has shown to distinguish adenocarcinoma from reactive mesothelium effectively.</span></p> <p class="MsoNormal" style="margin-bottom:0in;margin-bottom:.0001pt;line-height:
200%;mso-layout-grid-align:none;text-autospace:none"><b><span style="font-size:
14.0pt;line-height:200%;font-family:"Times New Roman","serif"">AIMS- </span></b><span style="font-size:14.0pt;line-height:200%;font-family:"Times New Roman","serif";
color:#231F20">Our aim was to validate and assess the Immunoreactivity profile of claudin-4 in a series of malignant and benign effusions.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom:0in;margin-bottom:.0001pt;line-height:
200%;mso-layout-grid-align:none;text-autospace:none"><b><span style="font-size:
14.0pt;line-height:200%;font-family:"Times New Roman","serif"">MATERIALS AND METHODS:-</span></b><span style="font-size:14.0pt;line-height:200%;font-family:
"Times New Roman","serif""> Total 84 samples were taken, 38 containing reactive mesothelial cells & 46 containing adenocarcinoma cells. <span style="color:#231F20">Claudin-4 immunohistochemistry was performed on cell-block paraffin sections and scored for staining intensity, staining pattern and percentage of positive tumor cells.<o:p></o:p></span></span></p> <p class="MsoNormal" style="margin-bottom:0in;margin-bottom:.0001pt;line-height:
200%;mso-layout-grid-align:none;text-autospace:none"><b><span style="font-size:
14.0pt;line-height:200%;font-family:"Times New Roman","serif"">RESULTS-</span></b><span style="font-size:14.0pt;line-height:200%;font-family:"Times New Roman","serif""> In 46 cases of metastatic adenocarcinomas, 44 cases were positive for<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom:0in;margin-bottom:.0001pt;line-height:
200%;mso-layout-grid-align:none;text-autospace:none"><span style="font-size:
14.0pt;line-height:200%;font-family:"Times New Roman","serif"">Claudin-4 & among the 38 non-malignant effusion cases where the fluid contained<o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom:0in;margin-bottom:.0001pt;line-height:
200%;mso-layout-grid-align:none;text-autospace:none"><span style="font-size:
14.0pt;line-height:200%;font-family:"Times New Roman","serif"">reactive mesothelial cells, none of them were positive for Claudin-4. Sensitivity & specificity of claudin-4 in diagnosing adenocarcinoma were 95.6% & 100% respectively.Positive Predictive Value & Negative Predictive Value of claudin-4 in diagnosing adenocarcinoma were 100% & 95% respectively<b>.</b><o:p></o:p></span></p> <p class="MsoNormal" style="margin-bottom:0in;margin-bottom:.0001pt;line-height:
200%;mso-layout-grid-align:none;text-autospace:none"><b><span style="font-size:14.0pt;line-height:200%;font-family:"Times New Roman","serif";
color:#231F20">CONCLUSIONS</span></b><span style="font-size:14.0pt;line-height:
200%;font-family:"Times New Roman","serif";color:#231F20">: Claudin-4 immunohistochemistry effectively distinguishes adenocarcinoma from reactive mesothelium with high sensitivity and specificity.<o:p></o:p></span></p>