Carbonic anhydrase IX (CAIX) does not differentiate between benign and malignant mesothelium

Area of Science:

• Oncology
• Pathology
• Biomarker Research

Background:

• Carbonic anhydrase IX (CAIX) is a marker for renal cell carcinoma.
• CAIX has recently been identified in malignant effusions.
• Understanding CAIX expression in effusions is crucial for differential diagnosis.

Purpose of the Study:

• To investigate the expression of CAIX in mesothelial cells within pleural and peritoneal fluids.
• To evaluate CAIX as a potential marker for identifying mesothelial cells in effusions.
• To compare CAIX expression in benign and malignant mesothelium.

Main Methods:

• Immunohistochemical staining of pleural and peritoneal fluids for CAIX, calretinin, Ber-EP4, and MOC31.
• Analysis of effusions from reactive, carcinomatous, and suspicious for mesothelioma cases.
• Tissue microarray analysis of benign and malignant mesotheliomas for CAIX expression.

Main Results:

• Mesothelial cells in both reactive and malignant effusions showed positive CAIX expression.
• CAIX expression in carcinomatous effusions was limited to mesothelial cells.
• High agreement (89%) was observed between CAIX and calretinin expression; CAIX was positive in 100% of benign and 91% of malignant mesothelium.

Conclusions:

• CAIX serves as a valuable ancillary marker for mesothelial cell identification.
• No significant difference in CAIX expression exists between benign and malignant mesothelium.
• Careful interpretation is required when assessing for renal cell carcinoma metastasis using CAIX.