CD74 (cluster of differentiation 74) acts as the chaperone of MHC-II (major histocompatibility) and is responsible for the trafficking of MHC-II molecules in APCs (antigen presenting cells). It also interacts with non-MHC proteins and functions as a receptor for MIF (macrophage migration inhibitory factor). MIF is a pleiotropic cytokine having pro-tumorigenic and pro-inflammatory functionality. It is involved in the progression and metastasis of hematologic and solid cancers, and its up-regulation in thyroid cancer might be linked with advanced tumor stage. In patients with malignant pleural mesothelioma, the over-expression of this protein functions as an independent prognostic marker for overall survival.