SLC22A17 and cancer: The intention of this article is: (i) to evaluate the positive or negative effects of free NGAL observed in various models of cancer by focusing on several aspects that have not been considered before (investigative techniques used to study NGAL’s role, NGAL isoforms, NGAL receptors); (ii) to consider the remaining challenges and; (iii) to discuss the prospects for determining NGAL’s functional value in cancer.