Moreover, using different biomarkers, such as the melanoma‐associated markers MCSP (melanoma‐associated chondroitin sulfate proteoglycan) and MCAM (melanoma cell adhesion molecule) and the melanoma initiating cell markers ABCB5, CD271, and RANK, Gray and collaborators have identified CTC subpopulations in MMPs 17. The gene discussed is ABCB5; the disease is melanoma.