Immunophenotyping by flow cytometry and frozen-section immunoperoxidase was compared on 21 consecutive lymph node biopsy specimens, of which a diagnosis of lymphoma was made for 11 specimens. Samples for flow cytometry were obtained by a fine-needle aspiration technique. Concordance between frozen-section immunoperoxidase and flow cytometry for all routine markers on all specimens ranged from 76 to 100%. In general, B-cell markers showed poorer concordance than T-cell markers, with kappa and lambda light chains having the poorest concordance, at 76% each. Flow cytometry was significantly more sensitive (90 versus 30%; P < 0.006) and had a significantly higher negative predictive value (100 versus 63%; P < 0.006) than frozen-section immunoperoxidase for demonstrating light-chain restriction. There was no significant difference in the specificities (100 versus 91%) or positive predictive values (100% each) between the two methods. Both methods demonstrated characteristic immunophenotypes for intermediate cell lymphomas, small lymphocytic lymphomas, and T-cell lymphoblastic lymphomas. Frozen-section immunoperoxidase and flow cytometry appear to be significantly concordant methods for immunophenotypic analysis of lymph node biopsies. Light-chain restriction is more readily demonstrated by flow cytometry than frozen-section immunoperoxidase. We believe that ex vivo fine-needle aspiration is a simple and reliable method of obtaining cell suspensions of lymph nodes for flow cytometry
