Relationship of T leukaemias with cerebriform nuclei to T-prolymphocytic leukaemia: a cytogenetic analysis with in situ hybridization

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.

Genetic alterations in Sezary syndrome

Sezary syndrome (SS) is a rare form of cutaneous T-cell lymphoma characterized by erythroderma and the presence of Sezary cells in the skin, lymph nodes, and peripheral blood. Over the past few decades, cytogenetic and molecular cytogenetic findings have revealed many genetic alterations in patients with SS. The most frequent genetic lesions include monosomy 10, losses of 10q and 17p, gains of 8q24 and 17q, and diverse structural alterations involving these regions. Expression patterns in regions of genomic imbalance show that a large number of genes in SS are deregulated, and this might have a causative role in oncogenesis. Overall, chromosomal instability is characteristic of this lymphoma and related to a poor prognosis, but no specific abnormalities that may be directly involved in development of the disease have yet been found.

High TCL1 expression and intact T-cell receptor signaling define a hyperproliferative subset of T-cell prolymphocytic leukemia

The T-cell leukemia 1 (TCL1) oncoprotein is overexpressed by chromosomal rearrangement in the majority of cases of T-cell prolymphocytic leukemia (T-PLL). In vitro, TCL1 can modulate the activity of the serine-threonine kinase AKT, a downstream effector of T-cell receptor (TCR) signaling. In a series of 86 T-PLL tumors, we show that expression of TCR, and levels of TCL1 and activated AKT are adverse prognostic markers. High-level TCL1 in TCR-expressing T-PLL is associated with higher presenting white blood cell counts, faster tumor cell doubling, and enhanced in vitro growth response to TCR engagement. In primary tumors and TCL1-transfected T-cell lines, TCR engagement leads to rapid recruitment of TCL1 and AKT to transient membrane activation complexes that include TCR-associated tyrosine kinases, including LCK. Pharmacologic inhibition of AKT activation alters the localization, stability, and levels of these transient TCL1-AKT complexes and reduces tumor cell growth. Experimental introduction and knockdown of TCL1 influence the kinetics and strength of TCR-mediated AKT activation. We propose that in T-PLL, TCL1 represents a highly regulated, targetable modulator of TCR-mediated AKT growth signaling.

Chronic lymphoid leukemias other than chronic lymphocytic leukemia: diagnosis and treatment

The World Health Organization classification divides lymphoid malignancies into precursor B-cell and T-cell neoplasms as well as mature B-cell and T-cell neoplasms. Mature B-cell neoplasms comprise more than 85% of non-Hodgkin lymphomas worldwide and can be further subclassified according to the postulated cell of origin by using specific morphologic, immunophenotypic, and molecular characteristics. Similarly, the more uncommon mature T-cell neoplasms have been better characterized to include numerous distinct entities with widely varying natural histories. The distinction between lymphoma and leukemia is somewhat arbitrary and is based on variable involvement of the bone marrow, peripheral blood, and lymphatic system. In this article, we review the diagnostic and clinical features of mature B-cell and T-cell lymphoproliferative disorders that commonly have a leukemic presentation.

Prolymphocytic leukemia

Prolymphocytic leukemia is a rare chronic lymphoproliferative disorder that includes two subtypes, B cell and T cell, each with its own distinct clinical, laboratory and pathological features. T-cell prolymphocytic leukemia has an aggressive course with short median survival and poor response to chemotherapy. With the use of the purine analogue pentostatin more than half of patients will have a major response and a minority will have a complete remission, usually lasting months. With the introduction of alemtuzumab, most patients who progressed despite treatment with pentostatin had a major response with a complete remission rate higher than that obtained with pentostatin when used as a first line. Unfortunately, progression still follows shortly. We recommend alemtuzumab as initial therapy and offer stem cell transplant (SCT) to selected young, healthy patients who respond. Although B-cell prolymphocytic leukemia is also a progressive disease, some patients can achieve a prolonged progression-free-survival with fludarabine. Patients presenting with massive splenomegaly may be effectively palliated with splenic irradiation or splenectomy. Rituximab is a promising agent and further investigations are warranted to better define its role in treatment of this disorder.

Mature T-cell leukemias

Mature T-cell and NK-cell leukemias are a group of relatively uncommon neoplasms derived from mature or postthymic T-cells accounting for a relatively small percentage of lymphoid malignancies. The recent availability of modern immunophenotypic and molecular tools has allowed a better distinction of these disorders from their B-cell counterparts. Similarly, identification of recurrent cytogenetic abnormalities, as well as plausible mechanisms through which these molecular events influence cellular signaling pathways, have created further insight into the pathogenesis of these disorders. Furthermore, the availability of new agents such as alemtuzumab has generated significant interest in devising specific therapeutic strategies for these malignancies. Herein, we review the clinical and pathological features of mature T-cell leukemias.

Bone marrow histopathology in peripheral T-cell lymphomas

Peripheral T-cell lymphomas (PTCL) account for 10-15% of all lymphoproliferative disorders in the western hemisphere. In PTCL, bone marrow biopsy is performed to establish the diagnosis, rule out other pathology, assess the extent of disease and monitor treatment response. The frequency and histology of bone marrow involvement varies greatly between different clinicopathological entities recognized by the World Health Organisation (WHO) classification, reflecting the differences in the underlying biology. Some lymphomas, such as angioimmunoblastic T-cell lymphoma, show nodular and/or interstitial pattern of infiltration with accompanying reactive changes. Others, including hepatosplenic T-cell lymphoma and large granular lymphocyte leukaemia, are characterized by intrasinusoidal infiltration. In many instances the pathological features are subtle and immunohistochemical and molecular studies are required for the diagnosis. Histological appearances may overlap with a variety of reactive T-cell proliferations and other malignancies. Furthermore PTCL frequently induce secondary changes in the marrow that may obscure the neoplastic infiltrate. The diagnosis often requires critical integration of the information obtained from clinical features, peripheral blood, bone marrow aspirate and biopsy findings. In this article we review the histopathology of bone marrow biopsy in PTCL within the context of the new WHO classification.

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)

Molecular cytogenetic characterization of Sézary syndrome

Sézary syndrome (SS) is a rare form of erythrodermic cutaneous T-cell lymphoma with hematological involvement and a poor prognosis. At present little is known about the molecular pathogenesis of this malignancy. To address this issue, we analyzed 28 SS cases through the use of molecular cytogenetic techniques. Conventional cytogenetic analysis showed 12 of 28 cases with clonal chromosome abnormalities (43%). Seven cases had aberrations affecting chromosomes 1 and 17; five demonstrated rearrangement of chromosomes 10 and 14; four presented with an abnormality of 6q. Multiplex-fluorescence in situ hybridization (M-FISH) revealed complex karyotypes in 6 of 17 cases (35%), and recurrent der(1)t(1;10)(p2;q2) and der(14)t(14;15)(q;q?) translocations were each identified in two cases, and confirmed by dual-color FISH. There was an overall difference in the incidence of clonal abnormalities detected by G-banded karyotyping and M-FISH. In addition, comparative genomic hybridization studies revealed chromosome imbalances (CIs) in 9 of 20 cases (45%), with a mean DNA copy number change per sample of 1.95 +/- 2.74, and losses (mean: 1.25 +/- 1.77) more frequent than gains (mean: 0.7 +/- 1.26). The most common CIs noted were loss of 1p, followed by losses of 10/10q, 17p, and 19, and gains of 17q and 18. Furthermore, in conjunction with this study a systematic literature review was conducted, which showed a high frequency and consistent pattern of chromosome changes in SS. These findings suggest that chromosomal instability is common in SS, although there are specific chromosomal abnormalities that appear to be characteristic, and the identification of two different recurrent chromosome translocations provides the basis for further studies.

Common clonal T-cell origin in a patient with T-prolymphocytic leukaemia and associated cutaneous T-cell lymphomas

An unusual course was observed in a patient with indolent T-prolymphocytic leukaemia (T-PLL) who subsequently developed mycosis fungoides (Mf), lymphomatoid papulosis (LyP) and cutaneous CD30+ anaplastic large cell lymphoma (ALCL). Polymerase chain reaction analysis demonstrated identical monoclonal T-cell receptor-beta and -gamma gene rearrangements in all the different clinical entities. Furthermore, cytogenetic studies revealed the same aberrant clone with trisomy of chromosome 8 in T-PLL and ALCL cells. This unique observation suggests that in T-PLL, the leukaemic cells might undergo secondary transformation, subsequently resulting in different phenotypes of cutaneous T-cell lymphoma.

Allelotyping in mycosis fungoides and Sézary syndrome: common regions of allelic loss identified on 9p, 10q, and 17p

Allelotyping studies have been extensively used in a wide variety of malignancies to define chromosomal regions of allelic loss and sites of putative tumor suppressor genes; however, until now this technique has not been used in cutaneous lymphoma. We have analyzed 51 samples from patients with mycosis fungoides and 15 with Sézary syndrome using methods to detect loss of heterozygosity. Micro satellite markers were selected on 15 chromosomal arms because of their proximity to either known tumor suppressor genes or chromosomal abnormalities identified in previous cytogenetic studies in cutaneous lymphoma. Allelic loss was present in 45% of patients with mycosis fungoides and 67% with Sézary syndrome. Loss of heterozygosity was found in over 10% of patients with mycosis fungoides on 9p, 10q, 1p, and 17p and was present in 37% with early stage (T1 and T2) and 57% with advanced disease (T3 and T4). Allelic loss on 1p and 9p were found in all stages of mycosis fungoides, whereas losses on 17p and 10q were limited to advanced disease. In Sézary syndrome high rates of loss of heterozygosity were detected on 9p (46%) and 17p (42%) with lower rates on 2p (12%), 6q (7%), and 10q (12%). There was no significant difference in the age at diagnosis or number of treatments received by those with loss of heterozygosity and those without, suggesting that increasing age and multiple treatments do not predispose to allelic loss. These results provide the basis for further studies defining more accurately chromosomal regions of deletions and candidate tumor suppressor genes involved in mycosis fungoides and Sézary syndrome.

p53 allele deletion and protein accumulation occurs in the absence of p53 gene mutation in T-prolymphocytic leukaemia and Sezary syndrome

In a series of 24 patients with chronic T-lymphoid disorders [13 T-prolymphocytic leukaemia (T-PLL) and 11 Sezary syndrome] we have studied (i) chromosome 17p abnormalities and p53 allele deletion by fluorescence in situ hybridization; (ii) mutation in the exons of the p53 gene by direct DNA sequencing; and (iii) p53 protein expression by immunocytochemistry and, in some cases, also by flow cytometry with DO-1, a monoclonal antibody to the p53 protein. The study revealed p53 deletion and accumulation of p53 protein in the absence of mutation in the exons that included the hot-spots and differs from that described in B-prolymphocytic leukaemia. Seven T-PLL and five Sezary syndrome patients had p53 overexpression, and five T-PLL and nine Sezary syndrome patients showed p53 deletion. Although the majority of cases with p53 accumulation had p53 deletion, the proportion of cells with the deletion did not correlate with the proportion of cells positive for p53 expression. Two cases of T-PLL showed strong p53 expression in the absence of p53 deletion, and one case of Sezary syndrome with p53 deletion in 97% of cells did not express p53. These findings suggest that a non-mutational mechanism exists for the accumulation of p53 protein in these T-cell disorders. The oncogenic effect of the accumulating wild-type protein has been reported in other malignancies. Whether haploidy resulting from p53 deletion contributes to this mechanism has yet to be determined. Alternatively, the frequent loss of the p53 gene could be associated with the deletion of an adjacent gene, which could be involved in the pathogenesis of these diseases.

T-cell prolymphocytic leukaemia: does the expression of CD8+ phenotype justify the identification of a new subtype? Description of two cases and review of the literature

T-cell chronic lymphocytic leukaemia (T-CLL) has recently been reclassified under the heading of T-cell prolymphocytic leukaemia (T-PLL) because of its unfavourable clinical course, independently of the morphologic features. This rare neoplasm usually shows CD4+/CD8- phenotype. Herein we report on two cases of T-PLL with CD8 expression that correspond to a possible variant of the disease first proposed by Hui et al. in 1987. These cases presented with malignant cells showing immunophenotypic features that can be easily identified and distinguished from other peripheral T-cell leukemias. However, the total number of cases studied is inadequate for defining a discrete clinico-pathologic entity with characteristic clinical features and cytogenetical abnormalities. An international collaboration in which tissue from similar cases is referred to a central pathologist for immunophenotyping and cytogenetical study, and clinical data are centrally compiled, may assist in defining this rare malady as a discrete clinico-pathologic entity.

Indolent course as a relatively frequent presentation in T-prolymphocytic leukaemia. Groupe Français d'Hématologie Cellulaire

T-prolymphocytic leukaemia (T-PLL) is a rare disorder with a poor outcome. Presentation features were studied in 78 T-PLL cases. Although 53 patients (group A) presented with typical progressive disease including rapidly increasing leucocytosis. 25 patients (group B) experienced an initial indolent clinical course with stable moderate leucocytosis. The morphology and antigenic profile of abnormal cells were similar in both groups, except for a lower incidence of CD45RO+ CD45RA- pattern in group B. A high incidence of inv(14)(q11;q32), t(14;14)(q11;q32) and i(8)(q10) chromosomal abnormalities were found in both groups. After an initial indolent phase (median 33 months; 6-103 months), 16 group B patients progressed to an aggressive stage with clinical and laboratory features similar to group A. Moreover, median survival after progression was short in both groups. In conclusion, T-PLL may start as an indolent disease similar to that reported in ataxia telangectasia. In this rare genetic disorder, some patients develop stable T-cell clones which progress toward T-PLL-like leukaemia. Moreover, ATM gene mutations have been reported in T-PLL. Thus, both diseases are likely to be closely related.

T-cell Prolymphocytic Leukemia

BACKGROUND: T-cell prolymphocytic leukemia (T-PLL) is a post-thymic T-cell malignancy with aggressive clinical course. Although T-PLL has been referred to under different designations, it is a distinct clinico-biological entity and should be distinguished from other T-cell disorders. METHODS: The literature on T-PLL is reviewed. Experience on the clinical and laboratory features, differential diagnosis, and therapy on a large series of T-PLL patients is presented. RESULTS: T-PLL affects adults and occurs more frequently in men. The principal disease characteristics are organomegaly, skin lesions, and a raised lymphocyte count. Immunological markers show a post-thymic T-cell phenotype (TdT- CD2+ CD5+ CD3ñ) with strong expression of CD7. A CD4+ CD8- phenotype is seen in two thirds of cases. CD4 and CD8 are coexpressed in 25%, and a CD4- CD8+ phenotype is rare. Cytogenetics show a recurrent abnormality inv(14)(q11;q32) that is always associated to other aberrations (particularly iso8q or trisomy 8). Differential diagnosis between T-PLL and other T-cell malignancies is based on a constellation of clinical and laboratory features. Generally, T-PLL patients are refractory to the therapy used in lymphoid disorders. Median survival is short but is improving with the use of 2'-deoxycoformycin and the humanized monoclonal antibody, anti-CDw52 (Campath-1H). CONCLUSIONS: T-PLL is a distinct T-cell disorder with characteristic clinical and laboratory features and a poor prognosis. A precise diagnosis of this disease is important in determining patient management and treatment.