Background: Bone marrow biopsies are routinely performed for staging patients with Bcell
non-Hodgkin lymphoma (NHL). In addition to histomorphological studies, ancillary
tools may be needed for accurate diagnosis. We investigated the clinical utility of multiparameter
flow cytometric examination of bone marrow aspirates.
Methods: A total of 248 bone marrow specimens from 232 patients diagnosed with B-cell
NHL were examined. Monoclonal antibodies directed against CD19, CD20, CD10 (or
CD5), and κ and λ immunoglobulins were used. Multi-stage sequential gating was performed
to select specific cells of interest, and the results were compared with bone marrow
histology.
Results: The concordance rate between histomorphology and flow cytometry was 91.5%
(n=227). Eight cases (3.2%) were detected by flow cytometry alone and were missed by
histomorphology analysis, and 6 of these 8 cases showed minimal bone marrow involvement
(0.09-2.2%). The diagnosis in these cases included large cell lymphoma (n=3),
mantle cell lymphoma (n=3), and mucosa-associated lymphoid tissue (MALT) lymphoma
(n=2). Thirteen cases were histopathologically positive and immunophenotypically negative,
and the diagnoses in these cases included diffuse large cell lymphoma (n=7), T-cell/
histiocyte-rich large B-cell lymphoma (n=2), anaplastic lymphoma kinase (ALK)-positive
large B-cell lymphoma (n=1), follicular lymphoma (n=1), MALT lymphoma (n=1), and
unclassifiable lymphoma (n=1).
Conclusions: Multi-color flow cytometry can be a useful method for assessing bone marrow
in staging NHL and also plays a complementary role, especially in detecting small
numbers of lymphoma cells.

Keywords: Bone marrow, Immunophenotyping, Flow cytometry, Non-Hodgkin lymphoma