Leukocyte-specific phosphoprotein-1 and PU.1: two useful markers for distinguishing T-cell-rich B-cell lymphoma from lymphocyte-predominant Hodgkin's disease.

BACKGROUND AND OBJECTIVES T-cell-rich B-cell lymphoma is a rare variant of diffuse large B-cell lymphoma. It shows morphologic, phenotypic and molecular similarities to lymphocyte predominant Hodgkin's disease, and in consequence the two diseases may sometimes be difficult to distinguish. In this paper, we have evaluated the usefulness of the pan-leukocyte marker LSP1 and the transcription factor PU.1 for resolving such diagnostic problems. DESIGN AND METHODS Immunohistochemical techniques were used to investigate the expression of LSP1 and PU.1 in 34 tumors, comprising typical examples of T-cell-rich B-cell lymphoma (15 cases), lymphocyte-predominant Hodgkin's disease (13 cases), and lymphocyte-rich classical Hodgkin's disease (6 cases). RESULTS The neoplastic cells of T-cell-rich B-cell lymphoma were LSP1-positive and PU.1-negative, whereas the lymphocytic and/or histiocytic (L&H) cells of lymphocyte-predominant Hodgkin's disease were mostly LSP1-negative, with variable PU.1 expression. The two markers did not discriminate between T-cell-rich B-cell lymphoma and lymphocyte-rich classical Hodgkin's disease, whilst they concurred to the distinction between lymphocyte-predominant and lymphocyte-rich classical Hodgkin's disease by integrating the already available tools. INTERPRETATION AND CONCLUSIONS Antibodies to LSP1 and PU.1 may represent useful reagents for the differential diagnosis between T-cell-rich B-cell lymphoma and lymphocyte-predominant Hodgkin's disease.