CA9 and carcinoma of esophagus: Driessen et al reported that CA9 expression was an independent prognostic marker in oesophageal cancers, especially adenocarcinomas and gastric cancer (Driessen et al, 2006), whereas in another study of oesophageal tumours, the degree of CA9 staining did not correlate with any of the pathological features examined (Turner et al, 1997).