Mature T-Cell leukemias: Challenges in Diagnosis

KLRG1 re-defines a leukemic clone of CD8 effector T cells sensitive to PI3K inhibitor in T cell large granular lymphocytic leukemia

T cell large granular lymphocytic leukemia (T-LGLL) is a clonal lymphoproliferative disorder, originated from mature effector memory CD8+ T cells. It is a challenge to define the leukemic T cell clones due to the lack of definite markers. Here, we decipher the heterogeneity of CD8+ T cells using cellular indexing of transcriptomes and epitopes by sequencing (CITE-seq) and T cell receptor (TCR) profiling in T-LGLL patients. A CD8+ terminal effector subset is identified, marked by reduced KLRG1 expression. Remarkably, high fidelity of leukemic clonality was specially limited in KLRG1- large granular lymphocytes (LGLs), not seen in KLRG1+ LGLs in T-LGLL patients or in KLRG1- LGLs in healthy controls. KLRG1- leukemic LGLs show upregulated PI3K signaling with enhanced cytotoxicity and exhaustion, persisting after conventional treatment. In a pilot trial of linperlisib (a PI3Kδ inhibitor) for refractory cases, 7 of 8 participants quickly respond with satisfactory safety. This study is registered at ClinicalTrials.gov (NCT05676710).

T-cell prolymphocytic leukemia, a case report and review of the literature

T-prolymphocytic leukemia is a rare and aggressive hematological malignancy characterized by the clonal proliferation of mature lymphoid T-cells. The pathogenesis of T-PLL is closely linked to specific chromosomal abnormalities, primarily involving the proto-oncogene T-cell leukemia/lymphoma 1 gene family. Recent advancements in molecular profiling have identified additional genomic aberrations, including those affecting the Janus kinase/signal transducers and activators of transcription (JAK/STAT) signaling pathway. This case report presents a patient with T-prolymphocytic leukemia whose cytogenetic and molecular analysis revealed a t(X;14)(q28;q11.2) translocation and a STAT5B mutation. Here, we aim to review the genetic and molecular underpinnings of T-prolymphocytic leukemia, as well as current treatment options, with a focus on the anti-CD52 monoclonal antibody alemtuzumab and JAK inhibitors. While alemtuzumab followed by allogeneic hematopoietic stem cell transplantation remains the standard of care for eligible patients, its efficacy is limited and many patients are ineligible. Emerging therapeutic approaches, such as JAK/STAT inhibitors, offer promising potential for improving patient outcomes.

Pediatric T-lymphoblastic Leukemia With an Entirely Mature Immunophenotype: A Prompt and Challenging Diagnosis

Children with T-ALL/LBL require prompt diagnosis and treatment. Flow cytometric analysis of T-lineage and immaturity markers usually leads to a straightforward diagnosis. However, rare cases of T-ALL expressing bright CD45 and lacking expression of immature markers can be a diagnostic conundrum and difficult to differentiate from mature T-cell lymphomas lacking surface CD3 expression or aberrantly expressing immature markers, which affects treatment decisions and prognosis. Here, we summarize the clinical, pathologic, and genetic features of 3 pediatric T-ALL cases with an entirely mature immunophenotype.

Genetic alterations in mature B- and T-cell lymphomas - a practical guide to WHO-HAEM5

The identification of recurrent genomic alterations in tumour cells has a significant role in the classification of mature B- and T-cell lymphomas. Following the development of new technologies, such as next generation sequencing and the improvement of classical technologies such as conventional and molecular cytogenetics, a huge catalogue of genomic alterations in lymphoid neoplasms has been established. These alterations are relevant to refine the taxonomy of the classification of lymphomas, to scrutinize the differential diagnosis within different lymphoma entities and to help assessing the prognosis and clinical management of the patients. Consequently, here we describe the key genetic alterations relevant in mature B- and T-cell lymphomas.

T-cell clonality testing for the diagnosis of T-cell large granular lymphocytic leukemia: Are we identifying pathology or incidental clones?

INTRODUCTION

T-cell clonality testing by T-cell receptor (TCR) gene rearrangement is key to the diagnosis of T-cell lymphoproliferative disorders such as T-cell large granular lymphocytic (T-LGL) leukemia. Benign clonal T-cell expansions, however, are commonly found in patients without identifiable disease, a condition referred to as T-cell clones of uncertain significance (T-CUS). In practice, T-cell clonality testing is performed for a range of reasons and results are often challenging to interpret given the overlap between benign and malignant clonal T-cell proliferations and uncertainties in the management of T-CUS.

METHODS

We conducted a 5-year retrospective cohort study of 211 consecutive patients who underwent PCR-based T-cell clonality testing for suspected T-LGL leukemia at our institution to characterize the use of T-cell clonality testing and its impact on patient management.

RESULTS

Overall, 46.4% (n = 98) of individuals tested had a clonal T-cell population identified. Patients with a monoclonal T-cell population were more likely to be older, have rheumatoid arthritis and have higher lymphocyte counts compared to patients with polyclonal populations. The majority of patients eventually diagnosed and treated for T-LGL leukemia had rheumatoid arthritis and lower neutrophil counts compared to untreated patients with monoclonal T-cell populations. A diagnosis of T-LGL leukemia was made in only a minority of patients (n = 48, 22.7%), and only a small proportion were treated (n = 17, 8.1%).

CONCLUSION

Our study suggests that T-cell clonality testing most commonly identifies incidental T-cell clones with only a minority of patients receiving a diagnosis of T-LGL leukemia and fewer requiring active treatment. These finding indicate an opportunity to improve utilization of T-cell clonality testing in clinical practice to better target patients where the results of testing would impact clinical management.

Molecular Features and Diagnostic Challenges in Alpha/Beta T-Cell Large Granular Lymphocyte Leukemia

Large granular lymphocyte leukemia is a rare chronic lymphoproliferative disease of cytotoxic lymphocytes. The diagnosis, according to the WHO, is based on a persistent (>6 months) increase in the number of LGL cells in the peripheral blood without an identifiable cause. A further distinction is made between T-LGL and NK-LGL leukemia. The molecular sign of LGL leukemia is the mutation of STAT3 and other genes associated with the JAK/STAT pathway. The most common clinical features are neutropenia, anemia, and thrombocytopenia, and it is often associated with various autoimmune conditions. It usually has an indolent course. Due to the rarity of the disease, no specific treatment has yet been identified. Immunosuppressive therapy is used and may allow for disease control and long-term survival, but not eradication of the leukemic clone. Here, we discuss the clinical presentation, diagnostic challenges, pathophysiology, and different treatment options available for alpha/beta T-LGL leukemia, which is the most common disease (85%), in order to better understand and manage this often misunderstood disease.