ANPEP and melanoma: High expression of CD13 can be detected in a number of human solid tumours, including melanoma (Menrad et al, 1993; Saiki et al, 1993; Fujii et al, 1995; Ishii et al, 2001; Hashida et al, 2002; Ikeda et al, 2003; Kehlen et al, 2003; Van Hensbergen et al, 2004), and a soluble form of CD13 has been shown to be highly increased in intratumoral fluids and ascites (Van Hensbergen et al, 2002).