This is consistent with our previous observations in in situ breast carcinoma (Wykoff et al, 2001) and similar observations made by others in invasive breast carcinoma (Ivanov et al, 2001), and with our in vitro findings that CA XII is regulated to some degree by hypoxia in breast tumour cells (Wykoff et al, 2000). This evidence concerns the gene CA12 and breast carcinoma in situ.