BCL-6 PROTEIN EXPRESSION IN HUMAN PERIPHERAL T-CELL NEOPLASMS IS RESTRICTED TO CD30(-CELL LYMPHOMAS() ANAPLASTIC LARGE)

The expression pattern of the BCL-6 transcription factor has been asse ssed in normal and neoplastic B-cell populations and in Hodgkin's dise ase. However, little is known about BCL-6 expression and its biologica l significance in T-cell neoplasms. In this study, a series of 59 lymp homa samples, including 27 CD30(+) anaplastic large-cell lymphomas (AL CLs), 24 other peripheral T-cell neoplasms, and 8 T-cell lymphoblastic lymphomas (T-LBLs), as well as a panel of t(2;5)-positive lymphoma-de rived human cell lines, were evaluated for BCL-6 protein expression by immunohistochemistry on frozen sections and cell smears. To define th e relationship between BCL-6 protein and CD30 antigen in CD30(+) ALCLs and in non-neoplastic lymph nodes, serial section immunohistochemistr y and two-color staining were used in selected CD30(+) ALCLs as well a s in reactive lymph nodes with non-neoplastic T-cell proliferations. B CL-6 protein was expressed in 12 of 27 (45%) CD30(+) ALCL cases, irres pective of their antigenic phenotypes (T-cell or null-cell type), and in the t(2;5)-positive cell lines. In contrast, the remaining 24 perip heral T-cell neoplasms as well as the 8 T-LBLs were considered negativ e for BCL-6 expression. Coexpression of CD30 and BCL-6, as detected in CD30(+) ALCLs, was also found in a subset of non-neoplastic lymphoid elements, namely the large lymphoid cells scattered in the interfollic ular areas of reactive lymph nodes. These findings suggest that CD30() ALCLs may represent the neoplastic transformation of extrafollicular CD30(+) cells and that BCL-6 may provide an additional marker for cha racterizing CD30(+) ALCLs. (C) 1997 by The American Society of Hematol ogy.