ABCB5 and melanoma: All patients with CTCs positive by RT-PCR for PAX3, ABCB5 or MLANA transcripts exhibited metastatic disease in distant organs (M1c) prior to treatment and two of the three cases with brain metastases were positive for PAX3 or MLANA. Interestingly, the fact that PAX3 and ABCB5 were detected in 6 out 7 cases with metastatic disease, positive by RT-PCR, might provide further evidence supporting the role of these genes in melanoma progression [14, 44, 47–50], but more importantly in the biology of melanoma CTCs.