The Differential Diagnosis of Lymphocyte-rich Classical Hodgkin's Lymphoma and Lymphocyte Predominant Hodgkin's Lymphoma Using the R.E.A.L. Criteria. An Immunohistochemical Study on 45 Cases.

In the present study, the two types, lymphocyte-rich classical HL (LRCHL) and nodular lymphocytepredominant type (NLPHL), which were grouped together before the R.E.A.L. classification, were questioned on the basis of differential criteria and 45 cases were retrieved from last ten years' archival material. On histopathological examination, nodular pattern, the cytological features and intensity of Reed- Sternberg (RS) cells, the pattern and intensity of histiocytes, the presence of germinal centers with progressive transformation were analysed. An immunohistochemical study was performed using antibodies against CD20, CD45RO, CD3, CD30, CD15 antigens and streptavidin-biotin procedure. The cases were classified into three groups according to the histologic pattern and immunophenotypical features ofthe RS cells: I) diffuse, LRCHL (CD20-, CD30+/-, CD15+/-): n= 28; II) NLPHL (CD20+, CD30-, CD15-): n= 11; III) cases which could not be evaluated in former groups: n= 6. Four cases in the latter group showed a nodular pattern with RS cells negative for all markers, except for one case, which expressed both CD20 and CD15. The remaining two cases exhibited a diffuse pattern and the RS cells were CD20+, coexpressing CD30 in one. These findings suggest that, differential diagnosis according to the R.E.A.L. criteria is not distinctive between the two categories of HL in about 13% of cases, and further criteria need to be established to define the grey zone between the two entities which might lead to further therapeutic trials.