[Differential diagnosis between nodular lymphocyte-predominant Hodgkin lymphoma and T-cell/histiocyte-rich B-cell lymphoma].

Objective To study the differential diagnosis between nodular lymphocyte-predominant Hodgkin lymphoma (NLPHL) and T-cell/histiocyte-rich B-cell lymphoma (TCRBCL). Methods 15 cases of NLPHL and 16 cases of TCRBCL were studied on both morphology and immunophenotype according to the WHO classification of lymphoid neoplasms. SP-immunohistochemical staining were performed on paraffin sections. In situ hybridization for EBER1/2 and gene rearrangement of immunoglobulin heavy chain (IgH) were carried out in 3 cases of NLPHL and 4 cases of TCRBCL, respectively. Results Histologically, a few atypical large cells scattered in a background of small lymphocytes with or without histiocytes were a common finding in both NLPHL and TCRBCL. Of NLPHL, nodular pathern predominated in 11 cases, diffuse patterns without nodules in 3 cases and one case showed nodular and diffuse pattern intermixed with a increased number of large cells. 14 cases of TCRBCL showed diffuse pattern. One case with micronodular pattern involving the splenic white pulp. One case showed a combination of nodules of NLPHL, diffuse areas of TCRBCL and a sheet of large cells of diffuse large B-cell lymphoma ( DLBCL) within the same lymph node biopsy specimen. Immunophenotypically, the large cells showed and CD20, CD79a, bcl-6 and EMA positive, and CD15, CD30, CD3, CD45RO and LMP-1 negative. In NLPHL, small B cells and CD57 positive cells were common, whereas in TCRBCL, TIA-1 positive cytotoxic cells and histiocytes dominated, small B cells were scarce or absent. EBER1/2 were negative and gene rearrangement of IgH was found in all tested 3 cases of NLPHL and 4 cases of TCRBCL, respectively. Conclusion There are some morphologic and immunophenotypic resemblance between NLPHL and TCRBCL. A combination of the morphological characteristics and the reactivity of the background cells for CD57 and TIA-1 seem to reliably discriminate between the entities and should therefore help to increase the interobserver reproducibility of diagnosis in the gray zone around Hodgkin lymphomas.