CA9 and neoplasm: In contrast to other CA isoenzymes, CA IX is normally present in only few normal tissues, namely in epithelia of the gastrointestinal tract, whereas it is abnormally induced in various human tumours including carcinomas of the kidney, lung, breast, colon, oesophagus, breast, uterine cervix, etc. (Pastorekova and Zavada, 2004).