Aberrant expression of membranous carbonic anhydrase IX (CAIX) is associated with unfavorable disease course in papillary and clear cell renal cell carcinoma

Abstract Objective Antibodies against carbonic anhydrase IX (CAIX) are often part of immunohistochemical panels used to assist renal cell cancer (RCC) subtyping. This study was undertaken to determine, whether assessing CAIX expression levels could provide additional prognostic information. Methods and materials More than 1,800 RCCs were analyzed in a tissue microarray (TMA) format for CAIX expression. All tumors had been reviewed and newly classified according to the WHO 2016 classification. Results Membranous CAIX expression revealed a “black and white” pattern that was strikingly dependent on the RCC subtype. In clear cell RCC, 89.2% of cancers showed strong positivity. The few clear cell RCC with lower CAIX expression levels were more likely to exhibit unfavorable tumor phenotype (p Conclusion Our data demonstrate that CAIX is a highly useful diagnostic biomarker for RCC providing both diagnostic and prognostic information.