DIFFERENTIAL-DIAGNOSIS BETWEEN CLASSIC HODGKINS LYMPHOMA, T-CELL-RICHB-CELL LYMPHOMA, AND PARAGRANULOMA BY PARAFFIN IMMUNOHISTOCHEMISTRY

There are significant difficulties in the differential diagnosis of ly mphomas at the interface between classic Hodgkin's lymphoma and both p aragranuloma and T-cell-rich B-cell lymphoma as well as at the interfa ce between T-cell-rich B-cell lymphoma and paragranuloma. We therefore investigated 197 cases (155 classic Hodgkin's lymphomas, 32 T-cell-ri ch B-cell lymphomas, and 10 paragranulomas) by paraffin immunohistoche mistry. Special interest was given to cases with a B-cell phenotype of tumor cells. The reactive inflammatory infiltrate in both classic Hod gkin's lymphoma and T-cell-rich B-cell lymphoma was rich in TIA-1-posi tive cytolytic lymphocytes, and CD57-positive cells were rarely encoun tered. In contrast, in paragranuloma CD57-positive cells and small B-l ymphocytes predominated the background infiltrate. The tumor cells in cases of classic Hodgkin's lymphoma were positive for CD30 in 95%, for CD15 in 75%, and for CD20 in 22%. Apart from this, vimentin was expre ssed in >95% of the cases. All cases of T-cell-rich B-cell lymphoma we re negative for vimentin, CD30, and CD15. The reactivity of the tumor cells for CD30, CD15, CD20, and vimentin together with the background reactivity for CD57 and TIA-1 seem to reliably discriminate between th e entities and should therefore help to increase the interobserver rep roducibility of diagnoses in the gray zone around Hodgkin's lymphoma.