CD79A is a membrane protein localized to the cell surface of B lymphocytes. CD79A forms a dimer with CD79B to comprise the B-cell antigen receptor (BCR), important for B cell development and function. It is expressed on all B cells from pre-B to plasma cell stages, and B-cell leukemias and lymphomas. In immunohistochemistry, it shows positive staining in B cells, plasma cells, B cell leukemia and lymphoma, Hodgkin’s lymphoma, myeloid leukemias, T cell leukemias and primary plasmacytoma of the lymph node. It is also useful for distinguishing preB lymphoblastic lymphoma from Ewing’s sarcoma. References: Mod Pathol 2001; 14:1175, PMID: 11706081; Mod Pathol 2004;17:1531, PMID: 15257313; Hum Pathol 1997;28:1083, PMID: 9308734.