Clinical and pathological prognostic markers for cutaneous melanoma, and molecules associated with tumour growth and metastasis that are released from melanoma cells into the bloodstream during the progression of disease (e.g., S100B, lactate dehydrogenase (LDH), S100A8/A9, soluble PD-L1, matrix metalloproteinase-9, 5-S-cysteinyl-dopa, melanoma inhibiting activity, tyrosinase mRNA, circulating-free DNA BRAFV600E mutation) are potential biomarker candidates (9–19). The gene discussed is MMP9; the disease is melanoma.