CA9 as a biomarker in preoperative biopsy of small solid renal masses for diagnosis of clear cell renal cell carcinoma.

Purpose: The purpose of our study was to test the utility of CA9 expression in preoperative biopsy samples to identify the ccRCC. Materials and methods: A total of 55 patients with a small solid renal mass (<= 4 cm) entered into this study. The immunohistochemical staining (51 samples) and RT-PCR (33 samples) were performed to detect CA9 expression. Results: For immunohistochemistry detection, CA9 was positive in 31/34 of biopsy samples of ccRCCs. CA9 was also positive in five suspected diagnosis of ccRCC. For RT-PCR detection, CA9 was positive in 25/25 biopsy samples of ccRCCs. The diagnostic accuracy of CA9 expression for ccRCC was 100%. RTPCR was performed in four biopsies where immunohistochemistry could not be performed because of limited tissue materials or necrosis. Two ccRCCs with a negative staining by immunohistochemistry were CA9 positive by RT-PCR. Conclusions: CA9 may be potentially useful biomarker in help making a diagnosis of ccRCC in the biopsy of renal mass. RT-PCR might be a preferred method to immunohistochemistry for the detection of CA9 in renal biopsy samples.