Immunohistologic detection of immunoglobulins in malignant lymphomas and its value in histopathologic diagnosis.

Formalin fixed, paraffin embedded material of malignant Non-Hodgkin lymphomas (132 cases), Hodgkin lymphomas (59 cases), angioimmunoblastic lymphadenopathy (2), lymphoepithelioid cell lymphoma (1) and lymph nodes with nonspecific lymphadenitis (8) were studied by a modified immunofluorescence technique for the presence and distribution of immunoglobulins (IgM, IgG, IgA, K, λ). Cells of lymphoblastic lymphomas of the convoluted type and of chronic lymphocytic leukemias were always Ig-negative. In immunocytic lymphomas tumor cells with morphologic features of plasma cells and plasma cell precursors always exhibited cytoplasmic Ig-staining showing monoclonality in two thirds of the cases (IgM/K, IgM/ λ, IgG/K, IgM/IgG/K). In extramedullary plasmacytomas all cells displayed a bright cytoplasmic Ig-staining. In centrocytic lymphomas and in centroblastic-centrocytic lymphomas a honeycomb-like pattern of Ig-staining could be observed. Some centroblasts in centroblastic-centrocytic lymphomas and in centroblastic lymphomas showed a granular (surface) staining in addition. Some lymphoblastic lymphomas of the Burkitt type and some of the morphologically 'unclassifiable' lymphoblastic lymphomas exhibited cytoplasmic fluorescence indicative of B-cell origin. In immunoblastic lymphomas almost 50% of the tumors investigated contained Ig-containing tumor cells again favouring their B-cell derivation. In cases of Hodgkin's disease some Hodgkin- and Reed-Sternberg-cells were positive for IgG/K. In angioimmunoblastic lymphadenopathy Ig-positive intercellular deposits were observed in addition to Ig-positive basement membranes of vessels, plasma cells and plasma cell precursors. All immunoglobulin classes could be detected in this localization though not in single cells. In lymphoepithelioid cell lymphoma (Lennert's lymphoma) only plasma cells and plasma cell precursors gave a positive staining and all immunoglobulin classes were present. In all lymphomas Ig-positive plasma cells and plasma cell precursors were found irrespective of the immunoglobulin content of the tumor cells and may, therefore, be interpreted as being reactive. On the basis of our studies it can be stated that immunomorphologic investigation of conventional biopsy material aids in characterization of Ig-producing lymphomas, and, hence, supplements the classical staining procedures. [ABSTRACT FROM AUTHOR]