Carbonic anhydrase C as a marker antigen in the diagnosis of choroid plexus papillomas and other tumours: an immunoperoxidase study.

Abstract

This study investigates the specificity of Carbonic Anhydrase C (CAC) as a marker antigen for choroid plexus papillomas and other primary and secondary brain tumours. Paraffin sections of normal brain, primary neuroepithelial tumours, and intracranial metastatic tumours were stained by the immunoperox-idase (PAP) technique for CAC, Glial Fibrillary Acidic Protein (GFAP) and S-100 protein. Normal choroid plexus contains CAC and S-100 but no GFAP whereas the six choroid plexus papillomas examined showed uniform staining for CAC and S-100 and patchy staining in the epithelium or stroma for GFAP. No other primary or metastatic tumour in the brain was found to contain CAC. Seven cases of colloid cyst from the third ventricle were totally negative for CAC, GFAP and S-100 protein. Oligodendrocytes in normal adult brain contain CAC in the cytoplasm and S-100 protein but they are negative for GFAP. In 5 cases of oligodendroglioma, no staining for CAC was seen in the tumour cells whereas many were stained for GFAP and S-100. Normal renal distal tubules, stomach epithelium and colon epithelium all contain CAC but carcinomas derived from these tissues do not. CAC was present in some tumour vessel endothelial cells. The results of this study suggest that (1) CAC is a reliable marker for choroid plexus papillomas and (2) colloid cysts may not be derived from neuroepithelial tissue.