Normal or reactive minor cell populations in bone marrow and peripheral blood mimic minimal residual leukemia by flow cytometry

Abstract

Background Measurable residual disease (MRD) is a strong independent poor prognostic factor for acute leukemia. Multiparameter flow cytometry (FCM) is a commonly used MRD detection method. However, FCM MRD detection is not well standardized, and the interpretation is subjective. There are normal/reactive minor cell populations in bone marrow (BM) and peripheral blood (PB), which could be confused with MRD. Methods The FCM data of 231 BM and 44 PB pediatric samples performed in a recent 15‐month period were retrospectively reviewed. These samples were from 56 B‐lymphoblastic leukemia (B‐ALL) patients, 11 T‐lymphoblastic leukemia (T‐ALL) patients, 28 acute myeloid leukemia (AML)/myelodysplastic syndrome (MDS) patients, 44 cytopenia/leukocytosis patients, and five patients with mycosis fungoides. Results There were over 10 normal or reactive minor cell populations identified with certain phenotypes mimicking MRD of acute leukemia. These mimickers included CD19+ NK cells, CD22+ basophils, CD22+ dendritic cells (DCs), and plasma cells for B‐ALL MRD; CD4/8 double‐negative T cells, CD4/8 double‐positive T cells, cytoplasmic CD3+ NK cells, CD2− T cells, CD7− T cells, CD5− gamma delta T cells, CD56+ NKT cells for T‐ALL MRD; CD33+ NK cells, CD117+ NK cells, basophils, plasmacytoid DCs, non‐classical monocytes, CD56+ and/or CD61+ monocytes for AML MRD. Conclusions These data confirm the presence of a variety of normal/reactive minor cell populations that could mimic MRD of acute leukemia by FCM. Recognizing these MRD mimickers is important for correct FCM MRD interpretation.

Oral azacitidine prolongs survival of patients with AML in remission independently of measurable residual disease status

“…34 Still, mutation-specific sequencing approaches may not detect evolving, subclonal populations of cells lacking the known founder mutation 22 and rare subpopulations of normal/transitory cells in both bone marrow and peripheral blood may mimic MRD, complicating MRD assessment with MFC. 35 Longitudinal molecular MRD assessments of patient samples in this study are currently under investigation, but are challenging because the QUAZAR AML-001 trial included only patients in remission, a high proportion of whom (53%) were MRD-at baseline. Also, the trial began in 2010, when it was not yet standard of care to obtain comprehensive molecular genetic data at the time of AML diagnosis.…”

Time point‐dependent concordance and prognostic significance of flow cytometry and real time quantitative PCR for measurable/minimal residual disease detection in acute myeloid leukemia with t(8;21)(q22;q22.1)

“…Two separate approaches have been used for assessing MRD by FCM: (a) the LAIP (Leukemia-Associated Immunophenotype) approach; (b) the different-from-normal (DFN) approach, which is based on the identification of aberrant differentiation/maturation profiles at follow-up. We used both approaches to define MRD burden (Li et al, 2021;Zhou et al, 2019), allowing identification of new aberrancies emerging at follow-up, that is, "immunophenotype shifts" (Al-Mawali et al, 2008;Baer et al, 2001;Langebrake et al, 2005), and monitoring patients in the absence of initial diagnostic information.…”

Use of multidimentional flow cytometry plots to improve measurable residual disease monitoring of acute myeloid leukaemias

“…Results suggest that DOAC STOP does not abolish detected LA results, therefore providing a valid method for detecting LA whilst on DOAC therapy. 3 Background: Acute myeloid leukaemia (AML) is a haematological malignancy with a prevalence of~1.5%. 1 Improved AML management requires increasingly sensitive measurable residual disease (MRD) detection, by either molecular or flow cytometric methods.…”

“…Other possible confounding factors include leukaemic subclones and treatment-related phenotypic changes. 3 We are currently conducting a prospective MRD study to better understand these findings.…”