Abstract Myelodysplastic neoplasms (MDS) are clonal hematopoietic disorders characterized by ineffective hematopoiesis, peripheral cytopenias, and a risk of progression to acute myeloid leukemia. As the disease originates in hematopoietic stem and progenitor cells (HSPCs), flow cytometry (FCM) has emerged as a key approach to interrogate the bone marrow CD34+ compartment, providing complementary information to morphology, cytogenetics, and molecular studies. This review summarizes current knowledge on CD34+ cell alterations in MDS, structured around three main axes: quantitative abnormalities, immunophenotypic aberrancies, and disruption of progenitor architecture. Based on these complementary abnormalities, the French CytHem‐SMD working group has developed an integrated flow cytometric strategy combining established diagnostic scores with leukemic stem cell and progenitor architecture analyses. We present this approach and ongoing efforts to standardize its implementation across laboratories, and discuss future developments which are expected to further improve the reproducibility and clinical utility of CD34+ compartment assessment in MDS.
Abstract The intraepithelial lymphogram, assessed by flow cytometry, has emerged as a valuable complementary tool for diagnosing celiac disease (CD). To optimize cutoff points for intraepithelial lymphocyte (IEL) subsets and to evaluate the diagnostic value of intraepithelial lymphogram in bulb and distal duodenal biopsies for active and potential CD in pediatric patients. This multicenter retrospective study included 190 pediatric patients (≤14 years old) who underwent duodenal biopsies for histological evaluation and flow cytometry. Patients were categorized as active CD ( n = 54), potential CD ( n = 69), and non‐CD controls ( n = 67). Total IELs, TcRγδ IELs, and sCD3 − IELs were quantified in bulb and distal duodenum biopsies. Cutoff points were optimized using ROC analysis. Agreement between cytometric patterns based on optimized and reference cutoffs was assessed using histological and serological criteria (Kappa coefficient). Sensitivity, specificity, and predictive values were evaluated for both biopsy sites. Active CD patients showed significantly increased total IELs and TcRγδ IELs, and decreased sCD3 − IELs in both anatomical regions. Optimized cutoff points for active CD were TcRγδ IELs >11.1% in the bulb and in the distal duodenum, sCD3 − IELs <6.4% in the bulb, and <8.5% in the distal duodenum. These cutoffs demonstrated stronger concordance with serological and histological findings than the reference values. Sensitivity improved when both anatomical regions were analyzed. In the potential CD group, a significant decrease in sCD3 − IELs was observed only in the bulb, where more patients exhibited a complete celiac lymphogram. Optimizing IEL subsets cutoff points and the inclusion of bulb biopsies enhances the diagnostic performance of intraepithelial lymphograms for active and potential CD in pediatric patients.
Aberrant antigen expression on mast cells (MCs) is one of the most accurate diagnostic markers for clonal MC diseases (CMCD). Although the coexistence of normal and pathologic MCs is frequently seen, the disease characteristics associated with it have been minimally investigated. We aimed to gain further insight into the relevance of partial aberrancy for establishing the diagnosis and risk stratification of systemic mastocytosis (SM) and monoclonal MC activation syndromes (MMAS). In patients with MMAS or SM, MC load, KIT D816V variant allele fraction (VAF), immunophenotype, mutational profile, basal serum tryptase (BST), and hematology parameters were evaluated to characterize the coexistence of normal and aberrant MCs. From 207 patients with CMCD, 75% of patients with MMAS, 67% with non-advanced SM (non-AdvSM), and 27% with advanced SM (AdvSM) exhibited partial aberrancy. This turned out to be one of the most discriminative parameters between indolent and advanced subtypes. Partial aberrancy was associated with less severe disease characteristics, that is, more indolent subtype, lower MC burden, KIT D816V VAF and BST, a mature MC immunophenotype, hematological parameters more closely corresponding to the normal-range values, and in a subgroup of patients with an SM-AHN, a less complex mutational profile. Assessing the coexistence of normal and pathologic MCs is a widely available, fast, and sensitive diagnostic and prognostic tool and may also be used in SM disease follow-up and treatment monitoring.
