Immunohistochemical demonstration of intracellular immunoglobulin in formalin fixed, paraffin embedded sections, as staining method in diagnostic work.

52 specimens from 34 patients with multiple myeloma and 3 cases with reactive plasmacytosis were stained by the 2-step labelled or 3-step unlabelled immunoperoxidase (IP) technique for demonstration of intracellular immunoglobulin in order to test the utility of these methods as staining methods in routine diagnostic work. The specificity of the methods was high as agreement between IP staining and serumanalysis for M-component was achieved in 27 out of 28 cases, where complete serumanalysis were available. Interpersonal variation in interpretation of the staining results was low. With optimal dilutions of antisera the evaluations of the examiners were concordant in 51 out of 52 specimens. By comparing the different tissue specimens the best result was obtained with iliac bone biopsies both concerning IP staining and morphological preservation. No difference was observed between results obtained by the 2-step labelled and 3-step unlabelled IP techniques.