CA9 and cancer: On the contrary, the real time quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) technology, representing a highly sensitive method for the detection of lymph node micrometastases, by virtue of its capacity to identify single tumor cells of epithelial origin, has been employed so far in a rather limited number of clinical studies, either in vulvar [21], cervical [11, 13, 22, 23], or endometrial [12] cancer, employing established epithelial markers like cytokeratin 19 [11, 13, 22] and cytokeratin 20 [12] or tumor-specific isozyme markers such as carbonic anhydrase 9 [21].