This assay (1) provided the best accuracy for DCC detection as a single-marker assay18; (2) demonstrated that every detected cancer cell increases the melanoma mortality risk17; (3) established that a DCCD around 100 marks microscopic metastasis formation2; and (4) revealed specific genetic alterations acquired at this metastatic colonization stage and DCCD2. The gene discussed is DCC; the disease is melanoma.