Roles of Flow Cytometry in Bone Marrow Staging of B-Cell Non-Hodgkin Lymphoma.

Background Bone marrow staging is important in determining the extent of disease and for making therapeutic decision in B-cell non-Hodgkin lymphoma (B-NHL). Flow cytometry has been widely used in this setting but its value has not been clearly demonstrated.

Objectives To determine the usefulness of bone marrow flow cytometry in staging of B-NHL.

Materials and Methods We compare the results of bone marrow studies using bone marrow aspirate (BMA), bone marrow biopsy (BMB) and three-color flow cytometry (FCM), in non-leukemic B-NHL patients performed during May 2003 to December 2006 at our institution and determine the concordant rate among these three methods in detecting bone marrow involvement by B-NHL.

Results Two hundred and sixty-eight bone marrow samples were analyzed in this study. Diffuse large B-cell lymphoma (DLBCL) was the most common histologic subtype (60.8%). Bone marrow (BM) involvement as confirmed by immunohistochemistry of BMB was observed in 66 samples (24.6%). Prevalence of BM involvement was slightly higher in indolent B-NHL (32.2%) as compared to aggressive B-NHL (20.8%). Agreement among all three methods was observed in 163 samples (60.8%). BMA had the sensitivity of 77.3% and specificity of 73.8%. FCM alone had the sensitivity of 63.6% and specificity of 89.6%. FCM failed to demonstrate clonal B-cells mainly in patients with focal involvement pattern. When FCM was combined with BMA, the sensitivity was increased to 87.9% but the specificity was decreased to 67.8%. They did not perform significantly better than using morphological criteria in BMB alone, which showed sensitivity of 80.3% and specificity of 94.5%.

Conclusion Based on these data, we conclude that flow cytometry may not be necessary in bone marrow staging of B-NHL in patients with non-leukemic presentation.