ANPEP and melanoma: It has been reported that APN/CD13 is overexpressed in several solid tumors (e.g., malignant melanoma, mesenchymal tumors, gynecological cancers, colorectal cancers, renal cancers, non-small cell lung cancer, and gastric carcinoma) and plays an important role in tumor-associated neoangiogenesis, tumorigenesis, and development of metastasis [29, 46].