Non-Hodgkin's lymphoma. Immunohistochemical and electron microscopical findings in relation to lightmicroscopy. A study of 74 cases.

From 74 patients with non-Hodgkin's lymphoma (NHL), fresh biopsy material from involved tissue was investigated histochemically and by light and electron microscopy. The results were compared with the light microscopical conclusions based on three currently utilized classifications, namely of Rappaport, Lukes, and Lennert. The separate groups of low-grade NHL appeared to consist of homogeneous cell populations, both in immunohistological as well as in enzymehistochemical and electron microscopical sense. On the contrary, high-grade NHL constituted a heterogeneous group in which supplementary (immunohistochemical, enzymehistochemical, and electron microscopical) investigation is very useful. All NHLs reacted with anti-human lymphocyte serum, including the so-called histiocytic NHLs according to the Rappaport classification, which proves their lymphocytic origin. Consequently the prefix "histiocytic" should be altered in a morphogenetically correct way. Without exception the B-cell NHLs were characterized by the presence of monoclonal immunoglobulin on the cell membrane and/or intracytoplasmically. In a part of the immunologically non-T-/non-B-/("null cell") NHLs, a B-cell origin was indicated by the presence of ATPase and/or 5' nucleotidase and a T-cell origin by the presence of dot-like acid phosphatase.