CA9 and neoplasm: As an optimal cut-off point, we defined 70% of the tumor samples (n = 51; CA9 mRNA level < 246, range: 0.63–246) with the lowest CA9 level as a low CA9 mRNA level, while the remaining 30% (n = 21) of the tumor samples were defined as overexpressing CA9 mRNA of ≥246.1 (range: 246.1–33779).