Clinical utility of carbonic anhydrase IX in diagnosing pleural mesothelioma

Background and objectives

Mesothelioma is an aggressive tumor with a poor prognosis. Histological diagnosis of mesothelioma using limited tissue samples can be challenging. Carbonic anhydrase IX (CAIX) is a transmembrane protein that is overexpressed in a variety of solid tumors. This study aimed to investigate the clinical utility of CAIX expression in the differential diagnosis of pleural mesothelioma from non-small cell lung carcinoma (NSCLC).

Methods

Unstained tissue microarray slides composed of 56 cases of pleural mesothelioma and 82 cases of NSCLC were subjected to immunohistochemical staining using a mouse anti-human antibody against CAIX.

Results

Of the 38 epithelioid mesothelioma cases, 34 (89%) displayed diffuse and strong cytoplasmic membrane reactivity, while the remaining four cases (11%) showed weak to moderate staining in tumor cells. Five out of sixteen (5/16) sarcomatoid mesothelioma cases were negative. Among the non-small cell lung carcinoma cases, 76% (32/42) of adenocarcinomas and 57% (21/37) of squamous cell carcinomas were completely negative, whereas the remaining cases showed focal weak expression of CAIX.

Conclusions

Our study demonstrates that CAIX expression has a high sensitivity (100%) in detecting pleural epithelioid mesothelioma, which is comparable to or better than currently used mesothelial markers. The specificity of CAIX is within a comparable range to that of commonly used mesothelial markers for differentiating epithelioid mesothelioma from NSCLC. Therefore, we recommend that CAIX immunohistochemistry staining be considered as an additional tool for the differential diagnosis of mesothelioma, particularly pleural epithelioid mesothelioma, from its common mimicker, NSCLC.