A study using immunomagnetic enrichment techniques to capture CTCs by utilization of MCAM, MCSP, ABCB5, and CD271 to compare populations of CTCs in circulation between individuals with primary and metastatic melanomas, found that CTC populations were significantly higher in metastatic melanoma (Figure 2A) (Freeman et al., 2012). The gene discussed is NGFR; the disease is metastatic melanoma.