Regarding CD13 expression in tumors, CD13 mRNA and protein seems to be abnormally overexpressed, i.e., in some samples of the melanoma, glioma, lung, liver, pancreatic, stomach, renal, prostate, testis, endometrial, and ovarian cancers [33, 34] (data from The Human Protein Atlas available at www.proteinatlas.org). Here, ANPEP is linked to melanoma.