Correlation between bone marrow histology and plasma cell immunophenotyping in patients with multiple myeloma under various treatments

The diagnostic and response criteria of multiple myeloma have been established by the International Myeloma Working Group. Although bone marrow morphology represents the gold standard both in the diagnostic and in the post-therapy practice, the role of multiparameter immunophenotyping by flow cytometry is currently gaining importance. The rapidity and high sensitivity to distinguish normal plasma cells from the pathological ones make this technique a precious tool, especially in defining the therapeutical response and in detecting minimal residual disease. We compared 92 simultaneous patterns of plasma cell immunophenotype and bone marrow morphology of multiple myeloma, after treatment with either chemoterapy alone or high-dose therapy with autologous or allogeneic stem cell transplantation. The aim was to determine the percentage of agreement of the two techniques in establishing the response to treatment. Discordant results were obtained in 6 cases, in which flow cytometry was able to correctly establish the degree of response to therapy. Our study shows the utility of using flow cytometry in response assessment in patients treated for multiple myeloma, with particular reference to patients in apparent complete remission and patients with oligoclonal bands observed after high-dose therapy.