Under these circumstances conventional molecular imaging offers tracking possibilities both preclinically and clinically (e.g. sodium iodide symporter (NIS) in thyroid metastases (Kogai and Brent, 2012; Portulano et al., 2014), glutamate carboxypeptidase 2 (PSMA) in prostate cancer (Oliveira et al., 2017; Perera et al., 2016), carcinoembryonic antigen in colorectal cancer (Tiernan et al., 2013), or melanin in melanomas (Tsao et al., 2012)). Here, FOLH1 is linked to melanoma.