CA12 and metastatic malignant neoplasm in the lymph nodes: Recently, Tafreshi et al. proposed that carbonic anhydrase isoforms 9 and 12, CAIX, and CAXII, respectively, were potential targets as reliable intrinsic biomarkers for cancer targeting, as one or the other of these two markers were found to be expressed in 100% of breast cancer lymph node metastasis surveyed [10].