Flow cytometry to detect bone marrow involvement by follicular lymphoma

Abstract

Background High‐quality data on bone marrow involvement (BMI) assessed by flow cytometry (FC) in follicular lymphoma (FL) is lacking. Aims We set up a prospective protocol with a 10‐color tube and acquisition of 500.000 leukocytes on a Nav flow cytometer for evaluation of BMI in FL by FC. Materials and methods FC was compared with a combination of histopathology and IGH gene rearrangement, which were considered the gold standard. We also compared BMI by FC with PET. Results Fifty‐two patients were included (median 67 years, 54% female). BMI by FC was seen in 35 (67%), with a median involvement of 1.2% (interquartile range: 0.3%–7%) of leukocytes. Comparison with the gold standard revealed two false negatives and two false positives (potentially true involvement undetected by the gold standard). BMI by PET was seen in 14/46 (30%). Immunophenotype of FL in the bone marrow was highly heterogeneous. The most common phenotypic abnormality was dim expression of CD19 (>0.5 log loss in 30% of patients). CD10 was negative in 13 (37%) and incompletely positive (overlap with the negative population) in a further 8 (28%) while entirely positive only in 14 (48%). Other abnormalities (loss of CD20, gain or loss of CD79b, expression of CD43, and substantial loss of CD45) were rare. Computational analysis by means of FlowSOM confirmed the heterogeneous phenotype, with FL from different patients clustering in unrelated metaclusters. Conclusion BMI by FL was frequent and immunophenotype was heterogeneous. However, this protocol enabled detection of FL in bone marrow in the vast majority of patients with bone marrow involvement by the gold standard.

19‐color, 21‐Antigen Single Tube for Efficient Evaluation of B‐ and T‐cell Neoplasms

“…CD38 is often dim or negative but can vary substantially (Fig. 4C) (Aren et al, 2022). GCB-type DLBCL and Burkitt lymphoma in this assay are commonly CD10 and CD38 bright (may be brighter than GCBs) may show increased FSC/SSC, though their phenotypes may otherwise vary substantially (Fig.…”

Assessment of Bone Marrow Involvement in B‐Cell non‐Hodgkin Lymphoma Using Immunoglobulin Gene Rearrangement Analysis with Next‐Generation Sequencing

“…BMI is typically assessed by histologic and immunohistochemical (IHC) analysis of bone marrow biopsies and aspirations [ 5 ]; however, histopathological detection of BMI has limitations, notably the possibility of false‐negative results in cases with nontypical histomorphologic features, minimal BMI, or inadequate specimens. Immunophenotyping with flow cytometry and molecular studies using immunoglobulin (Ig) gene rearrangement can aid in determining the clonality of lymphoproliferative tissues [ 1 , 6 , 7 , 8 , 9 , 10 , 11 ]. Recent studies demonstrate that positron emission tomography (PET)/computed tomography (CT) may possess adequate sensitivity for BMI assessment in some diffuse large B‐cell lymphoma (DLBCL) cases [ 12 , 13 ].…”