MOC31 for the Diagnosis of Metastatic Carcinoma and Mesothelial Lesions in Effusion Fluid—A Systematic Review and Meta-Analysis

<b>Background/Objectives:</b> MOC31 immunostain identifies carcinoma cells and is often used in effusion fluid cytology. This systematic review and meta-analysis aim to detail the diagnostic performance of MOC31 with subgroup analysis for different types of carcinomas. <b>Methods:</b> A literature search from five databases was performed. Relevant studies were reviewed for the calculation of pooled sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), diagnostic odds ratio (DOR), and area under the curve of hierarchical summary receiver operating characteristics (AUC-HSROC). Risk of bias, heterogeneity, and publication bias were assessed by the QUADAS-2, I2 index, and Deeks' funnel plot. <b>Results:</b> In total, 25 studies (10 retrospective cohorts, 10 case-control studies, and 5 case series) were included. The pooled sensitivity, specificity, NLR, PLR, and DOR were 0.926 (0.827-0.971), 0.932 (0.883-0.961), 0.079 (0.005-0.152), 13.610 (5.327-21.892), and 172.475 (83.150-428.100), respectively. The AUC-HSROC was 0.975, indicating excellent performance. Further analysis for adenocarcinomas, mesotheliomas, and benign/reactive mesothelial cells showed sensitivity for adenocarcinomas at 0.962 (0.948-0.975) and specificity for mesotheliomas and mesothelial cells at 0.934 (0.900-0.967) and 0.997 (0.994-1.000). Sensitivity in all four primary site subgroups (female genital, gastrointestinal/hepatobiliary, lung and breast) of adenocarcinoma were high (>0.910). Heterogeneity was observed, and meta-regression identified a trend for the year of publication. No evidence of publication bias was observed. <b>Conclusions:</b> Evidence shows that MOC31 could be a robust immunocytochemical marker for identifying and excluding metastatic carcinoma, with excellent diagnostic performance across types of adenocarcinomas. However, evidence is mainly from retrospective studies, highlighting the need for high-quality evidence to further establish MOC31diagnostic utility.