Clinical utility of bone marrow flow cytometry in B-cell non-Hodgkin lymphomas (B-NHL)

Aim: To determine the efficacy of flow cytometry (FC) in the assessment of bone marrow (BM) in B-cell non-Hodgkin lymphoma (B-NHL). FC is a common practice, but is far from being validated. Methods and results: Morphological analysis and FC immunophenotyping were perfomed on 421 samples. T-cell lymphomas, Hodgkin's disease, chronic lymphocytic leukaemia and hairy cell leukaemia were not included in the study. Clonality was assessed by the standard kappa/lambda/CD19 test. Aberrant immunophenotypes present in the B-cell subpopulation were also investigated. A double-step procedure was employed in all cases to increase the sensitivity of the FC procedure. Of 380 evaluable samples, 188 corresponded to follicular lymphoma (FL), 58 to diffuse large B-cell lymphoma (DLBCL), 57 to mantle cell lymphoma (MCL), seven to Burkitt's lymphoma and the remaining 70 samples to other low-grade lymphomas. Morphological marrow infiltration was found in 148 cases, and flow immunophenotyping identified 138 cases with BM involvement. A concordance between the two methods was detected in 298 cases (79%). There was a discordance in 82 cases (21%): morphology positive/FC negative in 46 cases and morphology negative/FC positive in 36 (61% of all cases with discordance were from FL). There was no difference in outcome when patients with discordances were compared with patients without discordances. Conclusions: Most samples showed concordance between morphological and FC results. FC identified BM involvement in the absence of morphological infiltration. Morphology/FC discordance seems to have no influence on the outcome of FL patients.