CAN MICROWAVE ANTIGEN RETRIEVAL REPLACE FROZEN-SECTION IMMUNOHISTOCHEMISTRY IN THE PHENOTYPING OF LYMPHOID NEOPLASMS - A COMPARATIVE-STUDY OF KAPPA AND LAMBDA LIGHT-CHAIN STAINING IN FROZEN-SECTIONS, B5-FIXED PARAFFIN SECTIONS, AND MICROWAVE UREA ANTIGEN RETRIEVAL

This study evaluates use of microwave antigen retrieval in 4 M urea to enhance detection of monoclonal kappa or lambda immunoglobulin in bre d tissue sections of B-cell lymphomas. Sixty-three lymphomas were eval uated in cryostat sections, results compared with staining in routinel y processed B5-fixed sections, and sections subjected to antigen retri eval prior to immunostaining. The microwave technique was optimal in B -cell immunoblastic lymphomas that expressed predominantly cytoplasmic immunoglobulin, staining 60% of cases compared with 50% in routinely processed sections and only 20% in cryostat sections. In the case of f ollicular center cell (centroblastic-centrocytic) lymphomas, cryostat sections detected monoclonal immunoglobulin in 81% of cases compared w ith 61% in microwaved sections and 52% in routine sections. Cryostat s ections remained indispensable in defining light chain expression in m any small cell (small lymphocytic, marginal zone, and mantle cell) lym phomas, because monoclonality was detected in 90% of cases in cryostat sections, but <40% in fixed sections. Although intensity of staining was greatest in microwaved sections, staining of background (stroma an d serum) was also increased with the microwave technique.