In melanomas, the loss of 5-hydroxymethylcytosine (5hmC), caused by decreased expression of TETs and of isocitrate dehydrogenases (IDH1 and IDH2), the latter coding for the enzymes that produce α-ketoglutarate, is a hallmark of this tumor, particularly to differentiate between melanomas and benign melanocytic nevi [114,115]. Here, IDH1 is linked to melanoma.