Evaluation of SOX6 immunohistochemical expression as a diagnostic marker in the distinction of epithelioid mesothelioma from lung carcinomas.

Epithelioid mesothelioma (EM) is a pleural malignancy whose many histopathologic patterns may overlap considerably with those of lung adenocarcinoma (LAC) or poorly differentiated squamous cell carcinoma (SCC). This study aimed to evaluate the diagnostic role of SOX6 immunohistochemical expression in EM, study its differential expression in EM, LAC, and SCC, and evaluate the utility of various combinations of SOX6 with established EM markers calretinin and D2-40. The study included 39 EM, 21 LAC, and 11 SCC cases. SOX6 expression was detected in 71.8 % of EM cases. Conversely, all SCC cases were SOX6-negative, and only two LAC cases were SOX6-positive (P < 0.001). The sensitivity and specificity of SOX6 in identifying EM was 71.8 % and 93.8 %, respectively. Calretinin and D2-40 expression was detected in 100 % and 97.4 % cases of EM, respectively. The diagnostic sensitivity of SOX6 for EM in combination with D2-40 and/or calretinin was higher than SOX6 as a solitary marker. Notably, the sensitivity of calretinin and/or SOX6 positive expression was 100 % higher than that of SOX6 combination with D2-40. Although the sensitivity of SOX6 is lower than that of other established markers for EM, it may be a fairly specific marker for the diagnosis of EM. Therefore, the inclusion of SOX6 into an immunohistochemical panel may have diagnostic utility in distinguishing between EM and lung carcinomas. However, more research is needed on a wider array of tumor types from various organs to truly understand its global specificity.