Morphologic, flow cytometric and cytogenetic evaluation of bone marrow involvement in B-cell lymphoma

Flow cytometric immunophenotypic analysis (FC) and cytogenetic analysis are essential techniques for the diagnosis and classification of many hematologic disorders. The roles of these analyses in B-cell lymphoma to detect bone marrow (BM) involvement in clinical staging and to evaluate the effectiveness of treatments have not yet been determined. The aim of this study was to evaluate the usefulness of FC and cytogenetic analysis in the assessment of BM involvement in B-cell lymphoma.

We retrospectively analyzed the usefulness of three-color FC and cytogenetic analysis in detecting BM involvement by examining 104 BM specimens from patients with B-cell lymphoma.

By morphologic evaluation of BM biopsy (BMB), the BM was involved in 11 specimens (10.6%), not involved in 92 specimens (88.5%) and involvement could not be determined in 1 specimen (0.9%). FC identified a monoclonal B-cell population in 24 samples (23.1%). FC detected BM involvement in all but one BMB positive sample, and showed negative results in a BMB undetermined sample. Conclusively, FC found a monoclonal B-cell population in 14 of 92 BMB negative samples (15.2%). In particular, FC detected smaller amounts of BM involvement than did morphologic evaluation. Cytogenetic analysis revealed clonal abnormalities in only 9 of 104 samples (8.7%). However, 2 of these 9 samples were from patients with aggressive lymphoma with complex structural chromosomal abnormalities detectable only by cytogenetic analysis.

Although morphologic evaluation of adequate amounts of BMB specimens remains essential for the evaluation of BM involvement, three-color FC is more sensitive in detecting BM disease than morphologic or cytogenetic analysis. Cytogenetic analysis seems to have low sensitivity and specificity, but this method may improve the detection of BM involvement in a small number of aggressive lymphomas that have many mitotic cells.