Transformation of T-cell large granular lymphocyte leukaemia into a high-grade large T-cell lymphoma

Cytotoxic peripheral T-cell lymphomas and EBV-positive T/NK-cell lymphoproliferative diseases: emerging concepts, recent advances, and the putative role of clonal hematopoiesis. A report of the 2022 EA4HP/SH lymphoma workshop

Cytotoxic peripheral T-cell lymphomas and EBV-positive T/NK-cell lymphoproliferative diseases were discussed at the 2022 European Association for Haematopathology/Society for Hematopathology lymphoma workshop held in Florence, Italy. This session focused on (i) primary nodal EBV-positive T and NK-cell lymphomas (primary nodal-EBV-TNKL), (ii) extranodal EBV-positive T/NK lymphoproliferative diseases (LPD) in children and adults, (iii) cytotoxic peripheral T-cell lymphomas, NOS (cPTCL-NOS), EBV-negative, and (iv) miscellaneous cases. Primary nodal-EBV-TNKL is a newly recognized entity which is rare, aggressive, and associated with underlying immune deficiency/immune dysregulation. All cases presented with lymphadenopathy but some demonstrated involvement of tonsil/Waldeyer's ring and extranodal sites. The majority of tumors are of T-cell lineage, and the most frequent mutations involve the epigenetic modifier genes, such as TET2 and DNMT3A, and JAK-STAT genes. A spectrum of EBV-positive T/NK LPD involving extranodal sites were discussed and highlight the diagnostic challenge with primary nodal-EBV-TNKL when these extranodal EBV-positive T/NK LPD cases demonstrate predominant nodal disease either at presentation or during disease progression from chronic active EBV disease. The majority of cPTCL-NOS demonstrated the TBX21 phenotype. Some cases had a background of immunosuppression or immune dysregulation. Interestingly, an unexpected association of cPTCL-NOS, EBV-positive and negative, with TFH lymphomas/LPDs was observed in the workshop cases. Similar to a published literature, the genetic landscape of cPTCL-NOS from the workshop showed frequent mutations in epigenetic modifiers, including TET2 and DNMT3A, suggesting a role of clonal hematopoiesis in the disease pathogenesis.

Transdifferentiation, phenotypic infidelity, progression, and transformation in T/NK-cell neoplasms: Report from the 2021 SH/EAHP Workshop

OBJECTIVES

Sessions 8 and 9 of the 2021 Society for Hematopathology and the European Association for Haematopathology Workshop aimed to collect examples of transdifferentiation, lineage infidelity, progression, and transformation in precursor and mature T/natural killer (NK)-cell neoplasms.

METHODS

Twenty-eight cases were submitted and analyzed, with whole-exome sequencing and genome-wide RNA expression analysis performed in a subset of the cases.

RESULTS

In session 8, 7 T-lymphoblastic lymphoma/leukemia cases were received that showed transdifferentiation to clonally related mature myeloid hematopoietic neoplasms, including 6 histiocytic/dendritic cell lineage neoplasms and a mast cell sarcoma. Session 9 included 21 mature T-cell neoplasms that were grouped into 3 themes. The first one addressed phenotypic infidelity in mature T-cell lymphomas (TCLs) and included 8 TCLs expressing aberrant antigens, mimicking classic Hodgkin and non-Hodgkin B-cell lymphomas. The second theme addressed disease progression in TCL and included 5 cutaneous T-cell lymphoproliferative disorders and 2 T-cell large granular lymphocyte proliferations with subsequent progression to systemic TCL. The third theme included 6 patients with TCL with T-follicular helper phenotype, mainly angioimmunoblastic T-cell lymphoma, with concurrent/subsequent clonal hematopoiesis or myeloid neoplasms and/or subsequent/concomitant diffuse large B-cell lymphoma.

CONCLUSIONS

This cohort of cases allowed us to illustrate, discuss, and review current concepts of transdifferentiation, aberrant antigen expression, and progression in various T/NK-cell neoplasms.

A suggested immunohistochemical algorithm for the classification of T-cell lymphomas involving lymph nodes

T-cell lymphomas are a heterogeneous group of neoplasms derived from mature T lymphocytes. These neoplasms are uncommon and usually diagnostically challenging. The focus of this article is to suggest an immunohistochemistry-based, practical approach to assist in the diagnosis of nodal T-cell lymphomas. These neoplasms fall into two major groups: those with many CD30+ tumor cells (group A) and neoplasms that are negative or show only partial expression of CD30 (group B). The differential diagnosis of group A neoplasms mainly includes ALK+ anaplastic large-cell lymphoma (ALCL), ALK-negative ALCL, mycosis fungoides with CD30+ large-cell transformation, adult T-cell leukemia/lymphoma, extranodal T-cell lymphomas involving lymph nodes (usually regional), and peripheral T-cell lymphoma, not otherwise specified (PTCL-NOS). Group B neoplasms also include two groups based on the presence or absence of T follicular helper (TFH) markers. Those neoplasms expressing at least 2 TFH markers include angioimmunoblastic T-cell lymphoma, nodal PTCL with a TFH phenotype, and follicular T-cell lymphoma. Neoplasms expressing ≤1 TFH marker can be further subdivided based on the expression of CD8 and cytotoxic markers and mainly include PTCL-NOS and a series of unusual subsets including primary Epstein-Barr virus-positive nodal natural killer/T-cell lymphoma, PTCL-NOS with a cytotoxic immunophenotype, and γ/δ T-cell lymphomas. Using this algorithmic approach, we suggest that the pathologist can establish a diagnosis for most nodal T-cell lymphomas encountered in daily practice.

Causes of double-negative T-cell lymphocytosis in children and adults

AIMS

The causes and diagnosis of 'double-negative' (CD3+CD4-CD8-) T-cell lymphocytosis are not well studied. We aimed to define the causes of double-negative T-cell lymphocytosis in children and adults, and to identify simple clinical and laboratory features that would help to differentiate between the underlying conditions.

METHODS

We collected clinical and laboratory data on 10 children and 30 adults with significantly increased peripheral-blood double-negative T-cells (>10% of total lymphocytes). We identified conditions associated with double-negative T-lymphocytosis with flow cytometry, peripheral-blood morphology and T-cell receptor-gene rearrangement studies. Patients were assigned to diagnostic categories on the basis of these test results.

RESULTS AND CONCLUSIONS

The causes of double-negative T-cell lymphocytosis in children were autoimmune lymphoproliferative syndrome (ALPS) and reactive γ/δ Τ-lymphocytosis. T-cell large granular lymphocyte (T-LGL) leukaemia, reactive γ/δ T-lymphocytosis and hepatosplenic T-cell lymphoma (HSTL) were the the most common disorders underlying double-negative T-cell lymphocytosis in adults. Less common causes included hypereosinophilic syndrome, peripheral T-cell lymphoma, ALPS and monoclonal, double-negative T-lymphocytosis of uncertain significance. CD5/CD7/Vδ2 expression and absolute double-negative lymphocyte count (<1.8×10⁹/L) were useful discriminators for distinguishing patients with reactive γ/δ T-lymphocytosis from those with γ/δ lymphoproliferative disorders. Differentiating between γ/δ T-LGL and HSTL can be difficult. Expression of CD57 and cellular morphology (pale cytoplasm with distinct granules) would support a diagnosis of γ/δ T-LGL.

Atypical Presentation of T-Cell Large Granular Lymphocytic Leukemia Mimicking Pleural Malignancy on 18F-FDG PET/CT

T-cell large granular lymphocytic leukemia is a rare form of leukemia, caused by clonal proliferation of cytotoxic T-cells, characterized by modest lymphocytosis and cytopenias of other lineage with hepatosplenomegaly and relatively rare lymph nodal involvement. Involvement of other organs is extremely rare. It is predominantly an indolent disease and most of patients remain asymptomatic for a long period. We present a rare case of aggressive form (CD56 positive) of large granular lymphocytic leukemia with atypical presentations mimicking pleural malignancy on F-FDG PET/CT.

Advances in the understanding and management of T-cell prolymphocytic leukemia

T-prolymphocytic leukemia (T-PLL) is a rare T-cell neoplasm with an aggressive clinical course. Leukemic T-cells exhibit a post-thymic T-cell phenotype (Tdt-, CD1a-, CD5+, CD2+ and CD7+) and are generally CD4+/CD8-, but CD4+/CD8+ or CD8+/CD4- T-PLL have also been reported. The hallmark of T-PLL is the rearrangement of chromosome 14 involving genes for the subunits of the T-cell receptor (TCR) complex, leading to overexpression of the proto-oncogene TCL1. In addition, molecular analysis shows that T-PLL exhibits substantial mutational activation of the IL2RG-JAK1-JAK3-, STAT5B axis. T-PLL patients have a poor prognosis, due to a poor response to conventional chemotherapy. Monoclonal antibody therapy with antiCD52-alemtuzumab has considerably improved outcomes, but the responses to treatment are transient; hence, patients who achieve a response to therapy are considered for stem cell transplantation (SCT). This combined approach has extended the median survival to four years or more. Nevertheless, new approaches using well-tolerated therapies that target growth and survival signals are needed for most patients unable to receive intensive chemotherapy.

Large granular lymphocytic leukemia. Current diagnostic and therapeutic approaches and novel treatment options

INTRODUCTION

Large granular lymphocytic leukemia (LGLL) is a low grade lymphoproliferative disorder characterized by the clonal proliferation of large granular lymphocytes (LGL) and recognised by the WHO. The diagnosis and management of these patients is challenging due to the limited information from prospective studies. Guidelines for front-line therapy have not been established. The prognosis is favourable with median overall survivals greater than 10 years. Areas covered: This manuscript is a review of the clinical features, diagnosis, pathogenesis and, in particular, the various available therapeutic options for this rare lymphoid leukemia. A systematic literature search using electronic PubMed database has been carried out. Expert commentary: A watch and wait strategy without therapeutic intervention is recommended in asymptomatic patients. The immunomodulators methotrexate, cyclophosphamide and cyclosporin are the most commonly used drugs in the routine practice with responses ranging from 50 to 65% and without evidence of cross-resistance among them. Purine analogs such as 2´deoxycoformycin and fludarabine alone or in combination may be indicated in patients with bulky and/or widespread disease. Trials using monoclonal antibodies such as Alemtuzumab and agents targeting the disrupted JAK/STAT pathway in LGLL such as JAK-3 inhibitors are promising particularly in a relapse setting.

Chronic lymphocytic leukemia transformation into high-grade lymphoma: a description of Richter's syndrome in eight dogs

Richter's syndrome (RS) is the development of an aggressive lymphoma in patients with chronic lymphocytic leukaemia (CLL). In humans, RS occurs in 2-20% of CLL, which transform into diffuse large B-cell lymphoma but reports in dogs are scarce. This study retrospectively describes eight dogs with CLL progressing into RS. A database including 153 dogs with CLL (93T CD8+ and 55 B-CLL) was interrogated and RS was demonstrated in eight cases (representing 5.2% of total CLL): two with T-cell (2.2% of T CLL) and six with a B-cell immunophenotype (10.9% of B-CLL). When RS occurred, lymphocytes were decreased compared to CLL. Five dogs had anaemia and two dogs thrombocytopenia. Frequent clinical signs included lymph node swelling, coughing, vomiting, neurological signs and weight loss. Independently from the therapy, RS was associated with a short survival (median 41 days). RS should be considered as an unfavourable evolution in canine CLL.

T-cell prolymphocytic leukemia in a 63-year-old female with a pre-existing T-cell large granular lymphocytic leukemia: metachronous T-cell leukemias with discordant subset restrictions (CD4 versus CD8) and distinct clonal identities

A 55-year-old female with T-cell large granular lymphocytic leukemia (T-LGL) (CD8+) was initially treated with anti-thymocyte globulin and then cyclosporine due to anemia/neutropenia. While the severity of cytopenia varied with the therapy, the T-LGL persisted. Eight years after the initial diagnosis, she developed lymphadenopathy and hepatosplenomegaly. A complete blood cell count revealed leukocytosis, anemia and thrombocytopenia with ∼ 80% lymphocytes. In contrast to the LGL cells, the blood lymphocytes at this time were medium-large in size and had oval/irregular nuclei, condensed chromatin, indistinct nucleoli and a moderate amount of basophilic cytoplasm, many with elongated vacuoles, and some with cytoplasmic projections. The abnormal lymphocytes comprised ∼ 30% of the bone marrow cellularity with interstitial infiltrates/aggregates. Immunophenotypic analyses demonstrated a T-cell neoplasm with features suggestive of T-cell prolymphocytic leukemia (T-PLL) (CD4+). Cytogenetic analysis revealed a novel clone with complex abnormalities. PCR-based TRG gene rearrangement studies detected a clonal amplicon distinct from that of the preexisting T-LGL. Because of the chronological sequence of the two T-cell neoplasms, this case was initially considered an aggressive transformation of T-LGL. However, this was ultimately excluded by a discordant CD4-subset restriction and the presence of a distinct clonal identity. While these two T-cell neoplasms may have intrinsic connections, the underlying pathogenesis remains to be investigated.

Guidelines for the management of mature T-cell and NK-cell neoplasms (excluding cutaneous T-cell lymphoma)

The peripheral T-cell neoplasms are a biologically and clinically heterogeneous group of rare disorders that result from clonal proliferation of mature post-thymic lymphocytes. Natural killer (NK) cell neoplasms are included in this group. The World Health Organization classification of haemopoietic malignancies has divided this group of disorders into those with predominantly leukaemic (disseminated), nodal, extra-nodal or cutaneous presentation. They usually affect adults and are more commonly reported in males than in females. The median age at diagnosis is 61 years with a range of 17-90 years. Although some subtypes may follow a relatively benign protracted course most have an aggressive clinical behaviour and poor prognosis. Excluding anaplastic lymphoma kinase (ALK)-positive anaplastic large cell lymphoma (ALCL), which has a good outcome, 5-year survival for other nodal and extranodal T-cell lymphomas is about 30%. Most patients present with unfavourable international prognostic index scores (>3) and poor performance status. The rarity of these diseases and the lack of randomized trials mean that there is no consensus about optimal therapy for T- and NK-cell neoplasms and recommendations in this guideline are therefore based on small case series, phase II trials and expert opinion.

Large granular lymphocyte leukemia

Clonal diseases of large granular lymphocytes (LGLs) represent a spectrum of clinically rare lymphoproliferative malignancies arising from either mature T-cell (CD3(+)) or natural killer (NK)-cell (CD3(-)) lineages. The clinical behavior of these disorders ranges from indolent to very aggressive. Patients with symptomatic indolent T-cell or NK-cell LGL leukemia are usually treated with immunosuppressive therapies; in contrast, aggressive T-cell or NK-cell LGL leukemias require intensive chemotherapy regimens. Novel targeted therapies are currently being tested in clinical studies.

[Large granular lymphocytic leukaemia]

BACKGROUND

Large granular lymphocytic leukaemia (LGL-leukaemia) is considered a rare disease. LGL-leukaemia is usually of the T-cell type, but a minority displays an NK-cell phenotype. Incidence and prevalence are unknown.

MATERIAL AND METHODS

We identified patients with LGL-leukaemia (with well-defined diagnostic criteria) diagnosed at Rikshospitalet University Hospital between 01.10.2001 and 31.12.2007. Their medical records were assessed retrospectively.

RESULTS

LGL-leukaemia was diagnosed in 52 patients, 26 women and 26 men, median age of 59 (26 - 86) years, during the study period. The leukaemia displayed NK-cell phenotype in one patient and T-cell phenotype in the remaining 51 patients. Slightly more than one third of the patients were asymptomatic. Cytopenia, mostly neutropenia, was usually the cause of the clinical phenotype in symptomatic patients. Co-morbidity with autoimmune disease was common, and we also found a high prevalence of clonal B-cell disease (17 %).

INTERPRETATION

Our data support the notion that LGL-leukaemia is under-diagnosed. Unexplained cytopenias should suggest the possibility of LGL-leukaemia, and appropriate diagnostic measures should be undertaken. An early diagnosis may save patients an extensive and unnecessary diagnostic work-up and ensure that a simple and effective treatment is offered.

Diseases of large granular lymphocytes

BACKGROUND

Clonal diseases of large granular lymphocytes (LGLs) are rare lymphoproliferative malignancies that arise from either mature T-cell (CD3+) or natural killer (NK)-cell (CD3-) lineages. They manifest a distinct biologic behavior that ranges from indolent to very aggressive.

METHODS

We discuss four distinct diseases involving LGLs: indolent T-cell LGL leukemia, aggressive T-cell LGL leukemia, chronic NK-cell leukemia, and aggressive NK-cell leukemia. Furthermore, we present an up-to-date systematic review of therapies for each entity.

RESULTS

Sustained LGLs, characteristic immunophenotype, clonal origin of leukemic cells, and clinical presentation are the most important features that distinguish indolent from aggressive subtypes of LGL leukemia and guide the selection of therapy. Patients with symptomatic indolent T-cell or NK-cell LGL leukemia are usually treated with immunosuppressive therapies in contrast to aggressive T-cell and NK-cell LGL leukemia, which require intensive chemotherapy induction regimens. Novel targeted therapies using monoclonal antibodies against receptors, including CD2, CD52, the beta subunit of the interleukin-2 receptor, and small molecules such as tipifarnib, are undergoing evaluation in clinical trials.

CONCLUSIONS

Future scientific advances focusing on the delineation of molecular pathogenic mechanisms and the development of new targeted therapies for each distinct LGL leukemia entity should lead to improved outcomes of patients with these disorders.

T-cell large granular leukemia and related proliferations

Session 9 of the 2005 Society for Hematopathology/European Association for Haematopathology Workshop focused on large granular lymphocyte (LGL) leukemias and related disorders. T-cell LGL (T-LGL) leukemias, discussed herein, account for 2% to 3% of cases of small lymphocytic leukemia. T-LGL diseases cover a heterogeneous spectrum of disorders that include reactive conditions, typically associated with autoimmune disease, to outright leukemia. These disorders are found in older people, with an average age at initial examination of approximately 60 years and a median survival of more than 10 years in T-LGL leukemia. Systemic symptoms and neutropenia are common at initial examination. Lymphocytosis, composed of small mature lymphocytes with increased cytoplasm, is common. The spleen and bone marrow are involved in T-LGL leukemia, although morphologic findings may be subtle. The immunophenotype is typically that of CD3+/CD8+ cytotoxic T cells. Some cases may be due to chronic immune stimulation, with subsequent clonal escape and proliferation of a neoplastic population of lymphocytes.

T-cell large granular lymphocyte leukemia

BACKGROUND

To the authors' knowledge, there is no standard treatment for patients with T-cell large granular lymphocyte (LGL) leukemia. Available data are limited by patient numbers and coexisting pathologies.

METHODS

The authors report on the use of immunosuppressants (cyclosporin A [CSA] and low-dose oral methotrexate [MTX] given continuously) and cytotoxic agents in the treatment of 29 patients with T-cell LGL leukemia age over the past 20 years.

RESULTS

The overall response rate (ORR) to MTX (n = 8 patients) was 85.7% (complete hematologic response [CHR] rate, 14.3%; partial response [PR] rate, 71.4%) with dose-dependent responses observed and safe usage of doses >10 mg/m2 per week in 2 patients. The ORR to CSA (n = 23 patients) was 78.2% (CHR rate, 30.4%; PR rate, 47.8%). The median time to response for both agents was 1 month. Toxicity, although it was minor in most patients and was more common in the CSA group, included second malignancies in 5 patients. An ORR of 67% (all CHR) was attained with pentostatin (n = 4 patients); recurrences developed after a median of 4.6 years. Successful retreatment with pentostatin was possible but with increasing drug resistance. Cyclophosphamide induced CHR that lasted >7 years with bone marrow clearance in 1 of 4 patients. Alemtuzumab induced a PR in 1 patient who had refractory disease.

CONCLUSIONS

Both MTX and CSA were efficacious in the treatment of T-cell LGL leukemia but generally required long-term maintenance therapy. The authors highlight the risks of second malignancies and persistence of bone marrow disease. Although MTX and CSA were effective as first-line therapy, alemtuzumab and pentostatin merit further investigation, particularly for refractory disease.

Pregnancy improves neutropenia in T-cell large granular lymphocyte leukaemia

The effect of pregnancy on T-cell large granular lymphocyte (LGL) leukaemia has not been previously described. We retrospectively reviewed the clinical features of three patients with T-cell LGL leukaemia; each of them had one or more pregnancies during disease evolution. Pregnancy was associated with sustained improvement in neutrophil count and concurrent reduction in lymphocytosis. Neutropenia returned in the non-pregnant state in all cases. A similar effect, induced by exogenous progesterone in one patient, suggests a role for progesterone in overcoming mechanisms of neutropenia in this disease. Pregnancy thus appears to have a beneficial effect on neutrophil count in T-cell LGL leukaemia.

Expression of the Tpl2/Cot oncogene in human T-cell neoplasias

Background

Tpl2/Cot oncogene has been identified in murine T-cell lymphomas as a target of MoMuLV insertion. Animal and tissue culture studies have shown that Tpl2/Cot is involved in interleukin-2 (IL-2) and tumor necrosis factor-α (TNF-α) production by T-cells contributing to T-cell proliferation. In the present report we examined a series of 12 adult patients with various T-cell malignancies, all with predominant leukemic expression in the periphery, for the expression of Tpl2/Cot oncogene in order to determine a possible involvement of Tpl2/Cot in the pathogenesis of these neoplasms.

Results

Our results showed that Tpl2/Cot was overexpressed in all four patients with Large Granular Lymphocyte proliferative disorders (LGL-PDs) but in none of the remaining eight patients with other T-cell neoplasias. Interestingly, three of the LGL-PD patients displayed neutropenia, one in association with sarcoidosis. Serum TNF-α levels were increased in all Tpl2/Cot overexpressing patients while serum IL-2 was undetectable in all subjects studied. Genomic DNA analysis revealed no DNA amplification at the Tpl2/Cot locus in any of the samples analyzed.

Conclusions

We conclude that Tpl2/Cot, a gene extensively studied in animal and tissue culture T-cell models may be also involved in the development of human LGL-PD and may have a role in the pathogenesis of immune manifestations associated with these diseases. This is the first report implicating Tpl2/Cot in human T-cell neoplasias and provides a novel molecular event in the development of LGL-PDs.

Clinicobiological, immunophenotypic, and molecular characteristics of monoclonal CD56-/+dim chronic natural killer cell large granular lymphocytosis

Indolent natural killer (NK) cell lymphoproliferative disorders include a heterogeneous group of patients in whom persistent expansions of mature, typically CD56(+), NK cells in the absence of any clonal marker are present in the peripheral blood. In the present study we report on the clinical, hematological, immunophenotypic, serological, and molecular features of a series of 26 patients with chronic large granular NK cell lymphocytosis, whose NK cells were either CD56(-) or expressed very low levels of CD56 (CD56(-/+dim) NK cells), in the context of an aberrant activation-related mature phenotype and proved to be monoclonal using the human androgen receptor gene polymerase chain reaction-based assay. As normal CD56(+) NK cells, CD56(-/+dim) NK cells were granzyme B(+), CD3(-), TCRalphabeta/gammadelta(-), CD5(-), CD28(-), CD11a(+bright), CD45RA(+bright), CD122(+), and CD25(-) and they showed variable and heterogeneous expression of both CD8 and CD57. Nevertheless, they displayed several unusual immunophenotypic features. Accordingly, besides being CD56(-/+dim), they were CD11b(-/+dim) (heterogeneous), CD7(-/+dim) (heterogeneous), CD2(+) (homogeneous), CD11c(+bright) (homogeneous), and CD38(-/+dim) (heterogeneous). Moreover, CD56(-/+dim) NK cells heterogeneously expressed HLA-DR. In that concerning the expression of killer receptors, CD56(-/+dim) NK cells showed bright and homogeneous CD94 expression, and dim and heterogeneous reactivity for CD161, whereas CD158a and NKB1 expression was variable. From the functional point of view, CD56(-/+dim) showed a typical Th1 pattern of cytokine production (interferon-gamma(+), tumor necrosis factor-alpha(+)). From the clinical point of view, these patients usually had an indolent clinical course, progression into a massive lymphocytosis with lung infiltration leading to death being observed in only one case. Despite this, they frequently had associated cytopenias as well as neoplastic diseases and/or viral infections. In summary, we describe a unique and homogeneous group of monoclonal chronic large granular NK cell lymphocytosis with an aberrant activation-related CD56(-/+dim)/CD11b(-/+dim) phenotype and an indolent clinical course, whose main clinical features are related to concomitant diseases.

T-cell large granular lymphocyte leukemia and related disorders

T-cell large granular lymphocyte (LGL) leukemia is a clonal proliferation of cytotoxic T cells, which causes neutropenia, anemia, and/or thrombocytopenia. This condition is often associated with autoimmune disorders, especially rheumatoid arthritis, and other lymphoproliferative disorders. The diagnosis is suggested by flow cytometry demonstrating an expansion of CD8(+)CD57(+) T cells and is confirmed by T-cell receptor gene rearrangement studies. Mounting evidence suggests that LGL leukemia is a disorder of dysregulation of apoptosis through abnormalities in the Fas/Fas ligand pathway. In most patients, this is an indolent disorder, and significant improvement of cytopenias can be achieved with immunosuppressive agents such as steroids, methotrexate, cyclophosphamide, and cyclosporin A. This review provides a concise, up-to-date summary of LGL leukemia and the related, more aggressive, malignancies of cytotoxic T cells and natural killer cells.

A systematic approach to diagnosis of mature T-cell leukemias reveals heterogeneity among WHO categories

The current World Health Organization (WHO) classification of hematopoietic malignancies defines several types of mature T-cell leukemia including T-cell prolymphocytic leukemia (T-PLL), Sezary syndrome (SS), and T-cell large granular lymphocytic (T-LGL) leukemia. These neoplasms can show overlapping features with each other and with T-cell lymphomas involving peripheral blood (PB). We analyzed the spectrum of clinicopatho-logic features in 102 mature T-cell leukemias and compared them to 10 hepatosplenic T-cell lymphomas that involved PB. T-PLL, defined as a T-cell leukemia showing rapidly rising PB lymphocyte counts, was the only tumor type expressing the oncoprotein TCL1 (71% of cases) and could present with relatively low lymphocyte levels or small tumor cell morphology. SS, defined by accompanying erythrodermic skin disease, was frequently associated with peripheral eosinophilia but could also develop high numbers of prolymphocytes, especially late in the disease course. T-LGL leukemia, defined by accompanying cytopenias or autoimmune phenomena (or both), had the best clinical outcome and generally showed the lowest circulating lymphocyte levels with only a few cases developing marked lymphocytosis. Using the dominant clinical or phenotypic feature, we describe here the degree of overlap among currently recognized WHO categories and identify areas where further clarification is needed. Our results indicate that incorporation of additional criteria, such as TCL1 expression status and hematologic parameters, can assist in a more accurate classification. (Blood. 2004;104:328-335)

Clonal T-cell Populations and Increased Risk for Cytotoxic T-cell Lymphomas in B-CLL Patients

Chronic lymphocytic leukemia (CLL) is associated with increased risk of malignancy, but the occurrence of other lymphomas, in particular T-cell lymphomas, is rare. We identified 7 cases of peripheral T-cell malignancy associated with B-cell-derived CLL from the files of two institutions over a 20-year period. The presence of both B and T lymphoproliferative disorders was confirmed in all cases by immunophenotype and in 6 cases by gene rearrangements. Six patients developed peripheral T-cell lymphoma (PTCL), unspecified, during the course of CLL (10-168 months). In all 5 evaluable cases, the cells had a cytotoxic T-cell phenotype; the sixth case was CD56+, but TIA-1 and Granzyme B could not be studied. A seventh patient with CLL developed mycosis fungoides, and an aggressive NK cell leukemia. To investigate possible risk factors for the development of PTCL, we screened 100 unselected peripheral blood samples from newly diagnosed CLL patients by PCR for the presence of clonal T cell populations. We found evidence of clonal T-cell expansion in 8 patients and increased lymphocytes with large granular lymphocyte morphology in 7 of 8 cases. The immunophenotype was assessed by multicolor flow cytometry and in 4 cases the T-cell expansion was composed of either CD3+/CD8+ or CD3+/CD4-/CD8- cells. The cytotoxic nature of the clonal T-cell expansions in the peripheral blood correlates with the cytotoxic nature of the PTCLs, but their role in the subsequent development of T-cell lymphomas is still unclear. PTCL following CLL should be distinguished from typical Richter syndrome, which it can mimic clinically.

Differential gene-expression profiling in the leukemia cell lines derived from indolent and aggressive phases of CD56+ T-cell large granular lymphocyte leukemia

As a rule, T cell large granular lymphocyte (T-LGL) leukemia runs a chronic clinical course without need for therapy. Some cases, however, progress to an aggressive disease after the indolent clinical stage. The transformation mechanism into a high-grade malignancy has not been well studied. We have established 2 leukemia cell lines, MOTN-1 and PLT-2, derived from the same clone of CD56+ T-LGL leukemia in chronic and aggressive phases, respectively. The paired availability of such cell lines is valuable in biologic and genetic investigation of T-LGL leukemia. We used a microarray containing 406 cDNAs to elucidate alterations of gene expression between the 2 cell lines. We found a number of genes that were differentially expressed: 13 genes with increased expression and 3 genes with reduced expression in PLT-2 cells as compared to MOTN-1 cells. Increased expression of the dek, rac, Op18, CD6, CD58, CD106, Id2, ATF4, IRF5, ELL2 and D6 genes, and reduced expression of the GzmA and GzmK genes were confirmed by real-time quantitative reverse transcription-PCR, whose results paralleled the microarray data. These upregulated genes encode oncoproteins, cell surface antigens including molecules related to T cell proliferation, transcription factors, and a chemokine receptor. The two downregulated genes encode granzymes that play an important role for induction of cell death. These findings suggest that there is differential gene expression in different clinical phases of T-LGL leukemia and these differentially expressed genes would be potential targets for further studies to identify the genes involved in the transformation process of T-LGL leukemia.