Immunophenotypic stability of T-cell large granular lymphocytic leukaemia by flow cytometry

High Incidence of Clonal CD8+ T-cell Proliferation in Non-malignant Conditions May Reduce the Significance of T-cell Clonality Assay for Differential Diagnosis in Oncohematology

Polymerase chain reaction (PCR) analysis of rearranged T-cell receptor (TCR) genes is a valuable diagnostic tool for differential diagnosis of T-cell large granular lymphocytic (T-LGL) leukemia and reactive lymphocytosis. Age-related narrowing of T-cells repertoire and expansion of immune or autoimmune clones may lead to false-positive results. The objective of this study was to evaluate the specificity and positive predictive value of PCR-based clonality assessment for a differential diagnostics of T-LGL leukemia. Rearrangements of TCRG and TCRB genes using the BIOMED-2 protocol were assessed in healthy individuals including the elderly (n = 62) and patients with rheumatic diseases (n = 14), transitory reactive CD8+ lymphocytosis (n = 17), and T-LGL leukemia (n = 42). Monoclonal TCRG/TCRB rearrangements in blood were identified in 11.3%/4.8% (7/3 of 62) of healthy individuals; 21.4%/14.3% (3/2 of 14) of patients with rheumatic diseases, and 17.6%/11.8% (3/2 of 17) of patients with reactive lymphocytosis. Immunomagnetic selection of lymphocytes in healthy individuals (31 of 33) revealed that clonal T-cells belong to CD8+ and CD57+ population. No clonal Vβ-Jβ TCRB rearrangements were found in the control group, only Dβ-Jβ TCRB and TCRG. Given the high detectability (96.7%) of Vβ-Jβ TCRB monoclonal rearrangements in patients with αβ-T-LGL leukemia, this marker had the greatest specificity and positive predictive value (100%; 99.2%). The presence of clonal CD8+CD57+ cells in blood is common for healthy individuals and patients with reactive conditions and may not associate with any malignancy. Different specificity of TCRG/ Dβ-Jβ TRB/ Vβ-Jβ TCRB PCR reactions should be taken into account for T-cell clonality data interpretation.

Flow Cytometry Applications in the Diagnosis of T/NK-Cell Lymphoproliferative Disorders

This article provides an overview of the role of flow cytometry in the diagnosis, prognosis, and follow-up of T and NK-cell lymphoproliferative disorders. For each category, we will briefly discuss the immunophenotypic features of normal T and NK cells, and address technical issues in flow cytometry, the approach to diagnosis in various contexts, pitfalls in interpretation, and its use in follow-up and post-therapy management. In addition to reviewing the diagnostic, prognostic, and therapeutic utility of flow cytometric immunophenotyping in several of specific T and NK cell entities, we will also cover some of the new immunophenotypic markers. Furthermore, we will touch upon incorporation of flow cytometry in the final diagnosis, including correlation with other ancillary tests. © 2019 International Clinical Cytometry Society.

Immunophenotypic stability of Sézary cells by flow cytometry: usefulness of flow cytometry in assessing response to and guiding alemtuzumab therapy

Flow cytometry (FC) is frequently used to detect aberrant peripheral blood (PB) T cells ("Sézary cells") in patients with mycosis fungoides (MF) and Sézary syndrome (SS). However, immunophenotypic stability of MF/SS over time is not well characterized. We analyzed 141 PB samples from 9 cases (2 SS, 7 MF). At diagnosis, there were 3 to 5 immunophenotypic aberrancies per case (median, 4), including dim or absent CD2, CD3, CD4, CD5, CD7, or CD26 and bright CD45RO. Of 9 patients, 7 had a subsequent change in immunophenotype. All patients retained multiple aberrancies at follow-up (median, 3 per analysis; range, 2-6), of which 22.0% (81/369) were new. In 5 patients, a more than 99% decrease in absolute Sézary cell (ASC) counts by FC after alemtuzumab therapy or total skin electron beam radiation was associated with clinical improvement. We observed minor immunophenotypic changes over time in most patients with MF/SS; however, the Sézary clones maintain persistently aberrant immunophenotypes and seem amenable to follow-up with limited FC panels. ASC counts by FC correlated well with clinical response.