[Differential "lymphoid cell infiltrates" diagnosis in bone marrow].

The purpose of this study was to provide criteria for the differentiation of reactive lymphoid hyperplasia (RLH) and focal involvement of the bone marrow by malignant lymphoma (ML). Using trephine bone-marrow biopsy specimens embedded in paraffin wax and unequivocally established samples with ML for comparison, all patients with questionable lymphoid or lymphohistiocytic marrow aggregates were re-examined, together with obviously reactive lesions. Following this procedure, a number of characteristics were found that differed in validity with regard to diagnosis. In addition to cytology, which is preferably assessed in Giemsa-stained specimens and evaluated by the Kiel classification, histotopography, fiber content, and immunohistochemical reactions are the most valuable tools for differential diagnosis. RLH is consistent with a central-perivascular localization, a distinctive border and the presence of germinal centers, no or only minimal reticulin fibrosis and a polyclonal reaction pattern with a mixed population of B- and T-lymphocytes, following staining with appropriate antibodies. In uncertain cases (i.e., extensive lymphoproliferations in HIV-myelopathy) the results of immunohistochemical staining are of definite importance for the diagnostic evaluation of these lesions.