CD56 is a single transmembrane glycoprotein also known as N-CAM (Neural Cell Adhesion Molecule), Leu-19, or NKH1. It is a member of the Ig superfamily. The 140 kD isoform is expressed on NK cells and NK-T cells. CD56 is also expressed in the brain (cerebellum and cortex) and at neuromuscular junctions. Certain large granular lymphocyte (LGL) leukemias, small-cell lung carcinomas, neuronal derived tumors, myelomas, and myeloid leukemias also express CD56. CD56 plays a role in homophilic and heterophilic adhesion via binding to itself or heparin sulfate.