Tyrosine hydroxylase, the first melanoma-associated marker (Tyr-OH) to have been proposed for CMC detection (Curry et al., 1996), was absent in “endothelial” (CD45–MCAM+) and “hybrid-endothelial/stem” (CD45–MCAM+/ABCB5+) populations, while positive (14.2%) only in the “stem” fraction (CD45–ABCB5+), in both early and advanced AJCC stage groups. The gene discussed is PTPRC; the disease is melanoma.