Several study results showed that the presence of hypermethylation in the promoter region of PTEN, TFPI2, RARB2, MGMT, and RASSF1A genes in ctDNA enabled differentiation of melanoma patients from healthy individuals [138,139,140], with elevated levels of methylated RASSF1A ctDNA more attributed to metastatic cases compared to early-stage melanoma [140]. This evidence concerns the gene PTEN and melanoma.