Hepcidin protein levels in the sera and HAMP mRNA expression in tumor tissues were first reported more than 10 years ago in a small cohort (n = 32) of metastatic ccRCC patients (Kamai et al., 2009), which showed a positive correlation of HAMP expression in serum or tumor tissue with cancer grade, tumor stage, distance metastasis, and serum IL-6 levels. Here, HAMP is linked to nonpapillary renal cell carcinoma.