The percentage of CA9-positive tumour cells was similar to that previously reported (Giatromanolaki et al, 2001) and was closely correlated between primary NSCLCs and brain metastases (r=0.825, P=0.0002), suggesting that there were similar levels of hypoxia in matched cases from this series (Table 1; Figure 1). This evidence concerns the gene CA9 and neoplasm.