Lipocalins as biochemical markers of disease have been extensively used. The clinical indications relate to almost any field of medicine, such as inflammatory disease, cancer, lipid disorders, liver and kidney function. Lipocalins are mainly extracellular carriers of lipophilic molecules, though exceptions with properties like prostaglandin synthesis and protease inhibition are observed for specific lipocalins. Lipocalin 2, a member of the lipocalin family that carries small lipophilic ligands, has gained recent attention as both a potential biomarker and a modulator of human cancers. Neutrophil gelatinase-associated lipocalin, also known as lipocalin 2, has been originally identified as a 25 kDa protein covalently linked to neutrophil gelatinase B. It is an acute phase protein involved in diverse physiological processes with an important role in intracellular iron transport. Moreover, lipocalin 2 is involved in the physiopathology of neoplastic process. Lipocalin 2 is a protein that has garnered a great deal of interest in multidisciplinary fields over the last two decades since its discovery. This review focuses on lipocalin 2 and its function.