CA9 and neoplasm: CA IX and CA XII were less frequently expressed than CA II in the tumour samples: 23% (n = 9, 8 MBs/1 PNET) of the tumours were positive for CA IX (3% strong, 13% moderate and 7% weak staining), and only 11% (n = 4, 3 MBs/1 PNET) of the tumours were positive for CA XII (3% strong, 3% moderate and 5% weak staining).