Aims: An accurate diagnosis of T-cell/histiocyte-rich large B-cell lymphoma needs to take into consideration those forms of Hodgkin's lymphoma also characterized by a predominance of small lymphocytes and histiocytes, i.e. nodular lymphocyte predominance Hodgkin's lymphoma and lymphocyte-rich classical Hodgkin's lymphoma. We have studied the clinical, phenotypic and genetic features of a series of 12 cases of T-cell/histiocyte-rich large B-cell lymphoma along with 18 cases of Hodgkin's lymphoma for comparative purposes.
Methods and results: Of the Hodgkin's lymphoma cases, there were 11 lymphocyte predominance type and seven classic type. T-cell/histiocyte-rich large B-cell lymphomas presented usually in advanced stages (III or IV in 11/12 cases), frequently with 'B' symptoms (6/9 cases), and followed a more aggressive course than Hodgkin's lymphoma (4/8 patients died due to the tumour in T-cell/histiocyte-rich large B-cell lymphoma versus 0/15 in Hodgkin's lymphoma). T-cell/histiocyte-rich large B-cell lymphoma cases showed diffuse effacement of the nodal architecture by a proliferation of scattered large atypical B-cells obscured by a background of small T-lymphocytes (more CD8+, TIA1+ than CD57+). Five cases showed also a prominent histiocytic component. The large B-cells expressed CD45 and often EMA (6/10 cases). On the other hand, CD 30, CD15 and latent infection by Epstein-Barr virus (EBV) were generally lacking. bc l6 and CD10 were, respectively, detected in 6/6 and 1/5 cases. Conventional polymerase chain reaction (PCR) showed monoclonal immunoglobulin heavy chain (IgH) gene rearrangements in all T-cell/histiocyte-rich large B-cell lymphomas studied (5/5), but did not detect any case with t(14;18) involving the major breakpoint region (0/4).
Conclusions: The differential diagnosis of T-cell/histiocyte-rich large B-cell lymphoma from Hodgkin's lymphoma is facilitated by the integration of different immunophenotypic, molecular and clinical findings. T-cell/histiocyte-rich large B-cell lymphoma is a monoclonal neoplasm of bc l6+ B-cells with a phenotypic profile similar to lymphocyte predominance Hodgkin's lymphoma, suggesting a germinal centre origin and a possible relation to this disease. Therefore, in order to distinguish it from lymphocyte predominance Hodgkin's lymphoma, characterization of the reactive background, IgH gene rearrangement studies by conventional PCR and clinical features are more useful. In contrast, T-cell/histiocyte-rich large B-cell lymphoma can be distinguished from classical Hodgkin's lymphoma thanks to the presence of monoclonal IgH rearrangement and the CD 30-CD15-CD45+EMA+ immunophenotypic profile of the neoplastic cells in T-cell/histiocyte-rich large B-cell lymphoma.