Cluster of differentiation 57 (CD57), also known as NK-1 (human natural killer-1) or Leu7 antigen, is an antigen detectable in natural killer cells, some T-lymphocytes and normal peripheral blood mononuclear cells, myeloid cells, and a variety of polypeptides, lipids, and chondroitin sulfate proteoglycans. CD57 is indicated as a marker for tumors of neuroendocrine origin, including pheochromocytomas, paragangliomas, carcinoid tumors, and medulloblastomas, as well as various neural tumors including neuromas, neurofibromas, schwannomas, and granular cell tumors. CD57 is also detectable in ganglioneuroma and prostate carcinoma. Anti-CD57 is used to distinguish nodular lymphocyte-predominant Hodgkin's lymphoma from T-cell / histiocyte-rich broad B-cell lymphoma, nodular sclerosis and Hodgkin's disease follicular lymphoma. Anti-CD57 can also be useful in separating thymoma from thymic carcinoma when combined with a panel that includes antibodies against CD5 and CD117.