ALK expression defines a distinct group of T/null lymphomas ("ALK lymphomas") with a wide morphological spectrum

ALK-negative anaplastic large-cell lymphoma demonstrates similar poor prognosis to peripheral T-cell lymphoma, unspecified

AIMS

Anaplastic large cell lymphoma (ALCL) is classically considered a clinicopathological entity separate from other nodal mature T-cell lymphomas (TCL). Recently, the anaplastic lymphoma kinase (ALK) protein was shown to identify a subgroup of nodal ALCL with an excellent prognosis, whereas ALK-negative ALCLs are more heterogeneous. The aim of this study was to investigate the clinicopathological parameters in relation to clinical behaviour of ALK-negative ALCL compared with other nodal mature TCL, i.e. peripheral TCL, unspecified (PTCL-NOS) and angioimmunoblastic lymphoma (AILT).

METHODS AND RESULTS

Clinicopathological data of ALK-positive (n = 28) and ALK-negative (n = 46) ALCL; PTCL-NOS (n = 47); and AILT (n = 12) were analysed for their prognostic significance. While ALK-positive ALCL shows favourable clinical features and a good prognosis, ALK-negative ALCL, PTCL-NOS and AILT are all associated with high age groups, advanced disease stage, and poor prognosis (<45% 5-year survival). In multivariate analysis of overall survival time, performed in the combined group of ALK-negative nodal mature T-cell lymphomas, only age and the International Prognostic Index (IPI) remained independent prognostic parameters, while lymphoma subtype (ALCL versus PTCL-NOS versus AILT) gave no additional information.

CONCLUSIONS

The distinction between ALK-negative ALCL and PTCL-NOS or AILT is of limited clinical relevance as they show comparable poor prognosis. In these lymphoma subtypes, only age and the IPI are of significant prognostic value.

Anaplastic lymphoma kinase proteins in growth control and cancer

The normal functions of full-length anaplastic lymphoma kinase (ALK) remain to be completely elucidated. Although considered to be important in neural development, recent studies in Drosophila also highlight a role for ALK in gut muscle differentiation. Indeed, the Drosophila model offers a future arena for the study of ALK, its ligands and signalling cascades. The discovery of activated fusion forms of the ALK tyrosine kinase in anaplastic large cell lymphoma (ALCL) has dramatically improved our understanding of the pathogenesis of these lymphomas and enhanced the pathological diagnosis of this subtype of non-Hodgkin's lymphoma (NHL). Likewise, the realisation that a high percentage of inflammatory myofibroblastic tumours express activated-ALK fusion proteins has clarified the causation of these mesenchymal neoplasms and provided for their easier discrimination from other mesenchymal-derived inflammatory myofibroblastic tumour (IMT) mimics. Recent reports of ALK expression in a range of carcinoma-derived cell lines together with its apparent role as a receptor for PTN and MK, both of which have been implicated in tumourigenesis, raise the possibility that ALK-mediated signalling could play a role in the development and/or progression of a number of common solid tumours. The therapeutic targeting of ALK may prove to have efficacy in the treatment of many of these neoplasms.

A ligand-inducible anaplastic lymphoma kinase chimera is endocytosis impaired

Ligand-induced membrane trafficking of the anaplastic lymphoma kinase (ALK) was studied using a chimeric receptor in which the extracellular and transmembrane domain of ALK was substituted for the corresponding regions of epidermal growth factor receptor (EGFR). Wild-type EGFR, EGFR/ALK and an EGFR/ALK kinase negative mutant were independently expressed in mouse NR6 fibroblasts. The capacity of EGFR/ALK to mediate [125I]-EGF internalization, receptor degradation and downregulation, which has never been previously described, was assayed. The rate of [125I]-EGF-induced internalization mediated by the cytoplasmic domain of ALK was reduced several fold compared with the wild-type EGFR. The low rate of EGF internalization promoted by EGFR/ALK correlated with an impaired degradation and downregulation of the receptor and indicate that ALK is not subject to traditional mechanisms used to regulate receptor tyrosine kinase function. Accordingly, ALK-activated intracellular domain does not associate in vivo with c-cbl and does not undergo ligand-mediated ubiquitination. The current study provides new insight into the function and regulation of ALK suggesting that the relative long membrane residence of activated ALK might confers a more potent and prolonged signaling activity. Indeed NR6-EGFR/ALK cells exhibited a approximately 3-fold increase in a maximal mitogenic response than NR6-EGFR.

Tyrosine phosphorylation in human lymphomas

In a previous study, we showed that the high level of protein tyrosine phosphorylation present in lymphomas containing an anaplastic lymphoma kinase (ALK) can be demonstrated in routinely processed paraffin tissue sections using immunolabelling techniques. In the present study we investigated whether oncogenic tyrosine kinase activation also occurs in other categories of lymphoma by staining 145 cases of lymphoma covering those tumours with a range of different subtypes including those with morphological similarity to ALK-positive anaplastic large cell lymphoma (ALCL). Twelve cases of the borderline malignant disorder lymphomatoid papulosis were also studied. Twenty seven of the 28 cases of ALK-positive ALCL showed the extensive cytoplasmic labelling for phosphotyrosine in the neoplastic cells. The remaining case containing moesin-ALK exhibited membrane-associated phosphotyrosine expression. There was no nuclear phosphotyrosine labelling in any of the ALK-positive ALCL, even though ALK was present within the cell nuclei in 23 of the tumours. Variable degrees of phosphotyrosine labelling, usually membrane-restricted, were observed in 7/40 cases of ALK-negative ALCL, 9/29 cases of diffuse large B-cell lymphoma, 3/6 cases of mediastinal B-cell lymphoma, 2/7 cases of Hodgkin's lymphoma, 3/6 cases of peripheral T-cell lymphomas unspecified, 4/6 cases of B-cell chronic lymphocytic leukaemia, 2/6 cases of follicular lymphomas and 2/12 cases of lymphomatoid papulosis studied. However none of these phosphotyrosine-positive cases showed the strong cytoplasmic labelling comparable to that seen in ALK-positive lymphoma. We conclude that activation of a tyrosine kinase is probably not a major oncogenic event in lymphomas other than ALK-positive ALCL.

Common ALK gene rearrangement in Asian CD30+ anaplastic large cell lymphoma: an immunohistochemical and fluorescence in situ hybridisation (FISH) study on paraffin-embedded tissue

AIMS

The most common recurrent genetic aberration in anaplastic large cell lymphoma (ALCL) is translocation involving the ALK gene that results in ectopic expression of ALK protein in lymphoid tissue. This study aims to investigate the frequency of ALK gene rearrangement in a series of Asian ALCL.

METHODS

ALK gene rearrangement was detected by immunostaining of ALK protein and fluorescence in situ hybridisation (FISH) targeting at the 2p23 region.

RESULTS

The expression of ALK protein was detected in 24/34 (71%) of the cases, and it was significantly higher in childhood cases (100%) when compared to adult cases (47%). The analyses by FISH were consistent with the results from immunostaining of ALK protein, but the analyses were only successful in 15/34 (44%) cases. FISH analyses detected extra copies of ALK gene in three cases, including one case that expressed ALK protein and showed 2p23 rearrangement.

CONCLUSIONS

The current series revealed a high frequency of ALK gene rearrangement, especially in the children. Immunostaining of ALK protein is a reliable indication of ALK gene rearrangement, and is superior to FISH. However, FISH analysis is useful in detecting other genetic aberrations that are not related to ALK gene rearrangement.

Recent developments in the biology and therapy of T-cell and natural killer-cell lymphomas

PURPOSE OF REVIEW

T-cell/natural killer (T/NK)-cell lymphomas represent a group of poor-risk lymphoproliferative disorders that have only recently been recognized as distinct clinicopathologic entities. The average outcome with currently available therapy is substantially inferior to that of aggressive B-cell lymphomas. Significant gaps remain in our knowledge of their origin, diagnosis, and clinical spectrum. This review outlines recent developments in the biology and molecular genetics of these disorders, current diagnostic challenges, and future avenues for therapy.

RECENT FINDINGS

Several cancer-prone transgenic mouse models that develop predominantly T/NK-cell lymphomas have been produced in the past 2 to 3 years. These models point to an important role for chronic cytokine stimulation and for disruption of genes involved in the control of chromatin remodeling and maintenance of genome integrity in the pathogenesis of T-cell lymphomas. The recognition of T/NK-cell lymphomas has been greatly facilitated by the broad acceptance of standard diagnostic criteria and by the increasing availability of assays for the analysis of T-cell receptor rearrangement and a more precise definition of functional T/NK-cell subsets. New drugs with potential for use in T/NK-cell lymphomas, including monoclonal antibodies, tyrosine kinase inhibitors, synthetic retinoids, immunoconjugates, and immunosuppressive molecules with novel mechanisms of action are in the early phase of clinical investigation.

SUMMARY

Much remains to be learned in the pathogenesis, clinical spectrum, and optimal therapy of T/NK-cell lymphomas. The availability of animal models of disease, new diagnostic tools, and targeted drugs with novel mechanisms of action should lead to rapid progress in this group of malignancies in the near future.

Detection of a subset of CD30+ anaplastic large cell lymphoma by interphase fluorescence in situ hybridization

T/null-cell anaplastic large cell lymphoma (ALCL) is a morphologically and clinically heterogeneous group of non-Hodgkin's lymphoma; to date several morphologic variants have been described on histologic specimens. However, the cytologic features of these variants in the fine-needle aspiration (FNA) specimens have not been well evaluated. The t(2;5)(p23;q35) has been identified in a subset of T/null-ALCL and is known to be associated with a favorable prognosis. We reviewed the cytomorphologic characteristics in 24 FNA specimens of ALCL. In all cases, the diagnosis was confirmed on histologic specimens, and immunohistochemical studies for anaplastic lymphoma kinase (ALK) protein expression were performed on the aspirates. The presence of ALK breakpoints were evaluated in nine cases, using a DNA break-apart probe on chromosome 2 covering the ALK gene by fluorescence in situ hybridization (FISH) techniques. Two hundred cells per case were examined. The results were expressed as the percentage of cells containing more than two signals of chromosome 2 to the total number of cells counted. FNA sites included lymph nodes (20), lung (2), breast (1), and soft tissue (1). The median age of the patients was 56 yr (range, 17-75 yr). Twenty cases had systemic involvement; in four cases, skin was the primary site with secondary involvement of the lymph nodes. All cases were CD30(+) by immunohistochemistry; 20 were of T-cell phenotype and 4 were null cell type. The cytologic evaluation revealed typical anaplastic morphology (common type) with many "hallmark cells" in 16 (67%) cases. Other morphologic variants identified were small cell pattern in five cases, monomorphic pattern in two cases, and lymphohistiocytic pattern in one case. FISH studies showed that six (66.7%) of nine cases had at least two signals of chromosome 2, consistent with ALK breakpoints. With careful cytomorphologic evaluation in conjunction with appropriate immunohistochemical studies, a diagnosis of ALCL can be confidently made in the FNA specimens in the cellular aspirates and its morphologic variants also can be recognized. Furthermore, the FNA specimen is suitable in detecting ALK breakpoints by FISH study, permitting rapid identification of a subset of patients with ALCL, who may have a favorable prognosis. Using a commercially available probe, detection of ALK breakpoints in the FNA specimens is simple and can be a useful diagnostic adjunct in cases where distinction from other lymphomas or lymphoid lesions is morphologically difficult.

The oncogenic fusion protein nucleophosmin-anaplastic lymphoma kinase (NPM-ALK) induces two distinct malignant phenotypes in a murine retroviral transplantation model

A t(2;5) (p23;q35) chromosomal translocation can be found in a high percentage of anaplastic large-cell lymphomas (ALCL). This genetic abnormality leads to the expression of the NPM-ALK fusion protein, which encodes a constitutively active tyrosine kinase that plays a causative role in lymphomagenesis. Employing a modified infection/transplantation protocol utilizing an MSCV-based vector, we were able to reproducibly induce two phenotypically different lymphoma-like diseases dependent on the retroviral titers used. The first phenotype presented as a polyclonal histiocytic malignancy of myeloid/macrophage origin with a short latency period of 3-4 weeks. Clinically, the diseased mice showed rapidly progressive wasting, lymphadenopathy and pancytopenia. Mice displaying the second phenotype developed monoclonal B-lymphoid tumors with a longer latency of approximately 12-16 weeks, primarily involving the spleen and the bone marrow, with less extensive lymph node but also histologically evident extranodal organ infiltration by large immature plasmoblastic cells. The described retroviral mouse model will be useful to analyse the role of NPM-ALK in lymphomagenesis in vivo and may contribute to the development of new treatment options for NPM-ALK induced malignancies.

ALK-negative systemic anaplastic large cell lymphoma: differential diagnostic and prognostic aspects--a review

Anaplastic large cell lymphoma (ALCL) can be divided into two major groups. The first is a spectrum of CD30+ T-cell lymphoproliferative disorders including primary cutaneous ALCL and lymphomatoid papulosis, usually affecting older patients but characterized by an excellent prognosis. The second is systemic nodal ALCL, which on the basis of genetic and immunophenotypic features combined with clinical parameters can be divided into two subgroups: anaplastic lymphoma kinase (ALK)-positive and ALK-negative systemic ALCL. ALK expression, usually the result of a t(2;5) translocation, correlates with the expression of other markers such as EMA and a cytotoxic phenotype, and is strongly related to younger age groups, lower international prognostic index (IPI) risk groups, and a good prognosis. ALK-negative ALCL, however, shows a more heterogeneous immunophenotype and clinical behaviour, and prognostic parameters are needed to determine treatment strategies in individual patients. Besides clinical parameters included in the IPI, recent studies have pointed out several biological prognosticators of potential value, such as the percentage of tumour-infiltrating activated cytotoxic T-lymphocytes. The expression of proteins involved in the execution or regulation of apoptosis, such as activated caspase 3, Bcl-2, and PI9, was also found to be strongly related to clinical outcome. These studies indicate that inhibition of the apoptosis cascade in particular is an important mechanism that can explain the poor clinical outcome in therapy refractory ALCL. Functional studies are required to investigate whether disruption of one or more of the apoptosis pathways is the major factor in the fatal outcome of the disease and whether apoptosis resistance based on inhibition of one pathway can be overcome by activating another pathway that is still intact.

Primary anaplastic large cell lymphoma of the central nervous system: prognostic effect of ALK-1 expression

Anaplastic large cell lymphoma (ALCL) rarely occurs in the central nervous system. Although defined by its composition of large, pleomorphic, CD30-positive lymphocytes, ALCL is heterogeneous. Most are T cell but some are null cell. Most but not all have a characteristic 2:5 translocation producing the fusion protein ALK-1, which is reliably detected by immunohistochemistry. In systemic ALCL, ALK-1 expression correlates with young patient age and a favorable prognosis. Herein we report four new cases of primary central nervous system ALCL from the Mayo Clinic and incorporate additional data from five previously published cases. ALK-1 expression was determined in all nine tumors. Patient age was 4-66 years (mean 29 years) with a bimodal distribution: 6 < or = 22 years, 3 > or = 50 years. Six were female. Tumors were mostly supratentorial, five were multifocal, and seven had involvement of dura or leptomeninges. Seven tumors were T cell, two were null cell, and five of nine were ALK-1 immunopositive. Total mortality was six of nine. Three patients, 4-18 years of age (mean 13 years), were alive at 4.8-6.1 years postdiagnosis; these tumors were all ALK positive. Five patients, 13-66 years of age (mean 43 years), died of tumor 4 days to 11 weeks postdiagnosis; four of five of these tumors were ALK negative. One 10-year-old child with an ALK-positive tumor died of sepsis, but in remission. Central nervous system ALCL is aggressive. Our study suggests that a better outcome may be associated with young age and ALK-1 positivity, prognostic parameters similar to systemic ALCL.

High-level expression of BCL3 differentiates t(2;5)(p23;q35)-positive anaplastic large cell lymphoma from Hodgkin disease

Anaplastic large cell lymphoma (ALCL) with t(2;5)(p23;q35) and Hodgkin disease (HD) share many cellular features, including expression of CD30. We compared gene expression profiles of 4 ALCL (Karpas 299, SU-DHL-1, DEL, SR-786) and 3 HD cell lines and found that BCL3, which encodes a nuclear protein belonging to the I kappa B family of inhibitors of nuclear factor-kappa B (NF-kappa B) transcriptional factors, was expressed at higher levels in ALCL than HD. Northern and Western blotting analyses confirmed the high-level expression of BCL3 in ALCL at both mRNA and protein levels. We established a real-time reverse transcriptase-mediated polymerase chain reaction assay to measure the BCL3 mRNA level and found a predominant level of BCL3 expression in t(2;5)(+) ALCL; the levels of cell lines and clinical materials were comparable to or higher than that of a B-cell chronic lymphocytic leukemia carrying t(14;19)(q32;q13). Southern blotting and fluorescence in situ hybridization disclosed that the BCL3 gene copies were amplified in SU-DHL-1, whereas Karpas 299 carried 4 BCL3 gene loci. The BCL3 gene contains 2 cytosine-guanine dinucleotide (CpG) islands, and the intragenic 3' CpG was entirely demethylated in SU-DHL-1 and DEL. In contrast to HD, in which NF-kappa B was constitutively activated, ALCL cells consistently showed (p50)(2) homodimer binding activity on electrophoretic mobility shift assay. It is suggested that the high-level nuclear Bcl-3 sequesters the (p50)(2) homodimer to the nucleus, which may account for the contradictory effect of CD30 stimulation on ALCL and HD. We propose that BCL3 is overexpressed by genetic and epigenetic modifications, potentially contributing to the development of t(2;5)(+) ALCL.

Cytologic and immunocytochemical findings of anaplastic large cell lymphoma: analysis of ten fine-needle aspiration specimens over a 9-year period

BACKGROUND

Anaplastic large cell lymphoma (ALCL) has raised much controversy in the field of hematolymphoid pathology. Its nature is becoming better characterized with recent advances in molecular genetics. However, to the authors' knowledge, a detailed description of the fine-needle aspiration (FNA) cytology of ALCL is lacking and the application of immunocytochemical study, including immunostaining for anaplastic lymphoma kinase (ALK) protein, to cytology samples has not been studied to date.

METHODS

The authors reviewed 10 FNA specimens of ALCL from 8 patients encountered at Pamela Youde Nethersole Eastern Hospital and Queen Mary Hospital in Hong Kong over a 9-year period from early 1993 to the end of 2001. The cytologic and immunocytochemical findings (including ALK protein overexpression) of the specimens were correlated with histologic and immunohistochemical findings of surgical biopsy specimens.

RESULTS

Six of the eight patients had ALCL of the common variant, whereas the remaining two patients had ALCL of the small cell variant. FNA specimens of ALCL of the common variant yielded many loosely dispersed "hallmark" cells that contained eccentric kidney-shaped or embryo-like nuclei, several prominent rod-shaped or angulated basophilic nucleoli, and abundant amphophilic cytoplasm. "Doughnut" cells, tumor cells with multilobated nuclei, and multinucleated giant cells with a wreath-like arrangement of nuclei occasionally were found. A small number of "plasmacytoid" tumor cells, nondescript small round tumor cells, and reactive polymorphs also was present. In contrast, "plasmacytoid" cells and nondescript small to medium-sized tumor cells represented the predominant cell population in ALCL of the small cell variant. The "plasmacytoid" appearance was exaggerated further in air-dried smears. In air-dried smears, small intracytoplasmic vacuoles and scanty azurophilic granules also were noted. On immunocytochemical study performed using the cell block materials, the majority of tumor cells demonstrated membranous and paranuclear "dot-like" positivity for CD30. The staining for epithelial membrane antigen, leukocyte common antigen, and T-cell markers was variable. Positive staining for ALK protein was demonstrated beautifully in two of the cases.

CONCLUSIONS

Despite the wide morphologic spectrum of ALCL, a definitive diagnosis on the basis of FNA cytology is possible on careful interpretation of the cytologic features and a high index of suspicion. The cytologic diagnosis can be confirmed further with proper application of immunostaining to cell block sections. Immunocytochemical study for ALK protein, which provides useful prognostic information, also can be demonstrated satisfactorily using cytology samples.

Primary anaplastic large cell lymphoma of the kidney

Primary renal lymphoma is a rare disease. There is still no agreement on its development primarily in this non-lymphoid organ. Some of the reported cases are questionable because of the incomplete staging of extrarenal disease. In the present study, we describe a rare case of a 73-year-old white man presenting with right flank pain. Physical examination did not reveal any peripheral lymphadenopathy or hepatosplenomegaly. An abdominal computerized tomography (CT) showed a large tumor in the right kidney with no enlarged liver, spleen or lymph nodes. On morphological and immunohistochemical examination, the tumor fulfilled the criteria of anaplastic large cell lymphoma (ALCL). A review of the literature revealed that this is the first reported case of primary ALCL of the kidney.

Molecular cytogenetic aberrations in CD30+ anaplastic large cell lymphoma cell lines

Anaplastic large cell lymphomas (ALCL) in children represent a heterogeneous group of neoplasms with regard to the cell lineages involved. The chromosomal 5q35 breakpoint (bp) and the expression of the NPM/ALK fusion gene are the most remarkable molecular cytogenetic features of these malignancies. To identify new locations of ALCL-related oncogenes, comparative genomic hybridization (CGH) was applied to three ALCL cell lines (SU-DHL-1, Karpas 299, and DEL) exhibiting the 5q35 bp and expressing the NPM/ALK transcript. The CGH profiles were compared with those obtained with DNA from U937, HL-60 cells, and altered lymph nodes from two children with ALCL. Significant DNA copy number gains and/or losses were observed on several chromosomes in all ALCL cell lines. Distinct amplicons were detected on 1q21 approximately q44 (DEL), 7q12 (SU-DHL-1), and 1q12 approximately q22 (Karpas 299) regions. The NPM/ALK fusion gene was confirmed by fluorescence in situ hybridization (FISH) analysis in more than 80% of interphase nuclei and metaphase spreads. Enhanced expression of TGF-beta2 and c-MET candidate genes located at the amplified regions was revealed in DEL and SU-DHL1 cell lines by Northern blot analysis. These findings delineate chromosomal imbalances in ALCL-derived cell lines in parallel with high level of amplification covering target DNA sequences, which could play a role in ALCL pathogenesis.

Molecular biology of anaplastic lymphoma kinase-positive anaplastic large-cell lymphoma

Anaplastic large-cell lymphoma (ALCL) provides an excellent example of how molecular insights into tumor pathogenesis are influencing and improving tumor classification. ALCL was described initially as a subtype of T-cell/null-cell lymphoma characterized by unusual tumor cell morphology and the expression of CD30. However, it was soon recognized that a subset of ALCLs contained chromosomal translocations involving anaplastic lymphoma kinase (ALK), a novel receptor tyrosine kinase gene. These rearrangements create chimeric genes encoding self-associating, constitutively active ALK fusion proteins that activate a number of downstream effectors, including phospholipase C-gamma, phosphoinositol 3'-kinase, RAS, and signal transducer and activator of transcription proteins, all of which seem potentially important in cellular transformation. Not all tumors classified as ALCLs have ALK rearrangements and, conversely, ALK rearrangements occur in lymphomas of widely varying morphology. Hence, only molecular markers can reliably identify ALK+ ALCL. The importance of doing so is reflected by clinical studies suggesting that ALK+ ALCLs have a significantly better prognosis than other aggressive peripheral T-cell or B-cell lymphomas, including ALK- ALCLs. The unique molecular pathogenesis of ALK+ ALCL is likely to lead to novel therapeutic approaches directed at specific inhibition of ALK or downstream effectors.

Peripheral T-cell lymphoma

Peripheral (post-thymic) T-cell lymphoma consists of a wide spectrum of disorders with marked differences in biology and behavior. Proper classification is pivotal for evaluating treatment results, and most studies performed a decade ago lump together different disease entities and cannot be interpreted. With improved use of immunophenotyping and molecular methods for these disorders, their exact nature is better defined in the Revised European-American Lymphoma and subsequent World Health Organization (WHO) classifications. The WHO classification of post- thymic T/natural killer (NK)-cell lymphoma consists of 15 entities, including about 30% that are unclassified cases. A wide range in incidence exists between different populations, but it is likely to be lower than previously estimated. Certain entities, like nasal/nasal-type T/NK-cell lymphoma and human T-cell leukemia/lymphoma virus 1, are much more prevalent in certain racial groups and show exquisite viral association. In these entities as a group, prognosis and treatment seem inferior to those of their B-cell counterparts, but treatment must be tailored to the exact pathologic diagnosis and prognostic index. Aggressive combination chemotherapy appears to be curative for certain entities (eg, anaplastic lymphoma kinase-positive), whereas purine analogues may be useful for low-grade entities. The role of autologous and allogeneic stem cell transplantation is still poorly defined. Specific antibody-based therapy is also on the horizon.

Identification of novel fusion partners of ALK, the anaplastic lymphoma kinase, in anaplastic large-cell lymphoma and inflammatory myofibroblastic tumor

ALK-positive anaplastic large-cell lymphoma (ALCL) has been recognized as a distinct type of lymphoma in the heterogeneous group of T/Null-ALCL. While most of the ALK-positive ALCL (ALKomas) are characterized by the presence of the NPM-ALK fusion protein, the product of the t(2;5)(p23;q35), 10-20% of ALKomas contain variant ALK fusions, including ATIC-ALK, TFG-ALK, CLTC-ALK (previously designated CLTCL-ALK), TMP3-ALK, and MSN-ALK. TMP3-ALK and TMP4-ALK fusions also have been detected in inflammatory myofibroblastic tumors (IMTs), making clear that aberrations of the ALK gene are not associated exclusively with the pathogenesis of ALK-positive ALCL. Here we report results of molecular studies on two lymphoma cases and one IMT case with variant rearrangements of ALK. Our study led to the detection of the CLTC-ALK fusion in an ALCL case and to the identification of two novel fusion partners of ALK: ALO17 (KIAA1618), a gene with unknown function, which was fused to ALK in an ALCL case with a t(2;17)(p23;q25), and CARS, encoding the cysteinyl-tRNA synthetase, which was fused to ALK in an IMT case with a t(2;11;2)(p23;p15;q31). These results confirm the recurrent involvement of ALK in IMT and further demonstrate the diversity of ALK fusion partners, with the ability to homodimerize as a common characteristic.

A ligand-inducible epidermal growth factor receptor/anaplastic lymphoma kinase chimera promotes mitogenesis and transforming properties in 3T3 cells

Oncogenic rearrangements of the anaplastic lymphoma kinase (ALK) gene, encoding a receptor type tyrosine kinase, are frequently associated with anaplastic large cell lymphomas. Such rearrangements juxtapose the intracellular domain of ALK to 5'-end sequences belonging to different genes and create transforming fusion proteins. To understand how the oncogenic versions of ALK contribute to lymphomagenesis, it is important to analyze the biological effects and the biochemical properties of this receptor under controlled conditions of activation. To this aim, we constructed chimeric receptor molecules in which the extracellular domain of the ALK kinase is replaced by the extracellular, ligand-binding domain of the epidermal growth factor receptor (EGFR). Upon transfection in NIH 3T3 fibroblasts, the EGFR/ALK chimera was correctly synthesized and transported to the cell surface, where it was fully functional in forming high versus low affinity EGF-binding sites and transducing an EGF-dependent signal intracellularly. Overexpression of the EGFR/ALK chimera in NIH 3T3 was sufficient to induce the malignant phenotype; the appearance of the transformed phenotype was, however, conditionally dependent on the administration of EGF. Moreover, the EGFR/ALK chimera was significantly more active in inducing transformation and DNA synthesis than the wild type EGFR when either was expressed at similar levels in NIH 3T3 cells. Comparative analysis of the biochemical pathways implicated in the transduction of mitogenic signals did not show any increased ability of the EGFR/ALK to phosphorylate PLC-gamma and MAPK compared with the EGFR. On the contrary, EGFR/ALK showed to have a consistently greater effect on phosphatidylinositol 3-kinase activity compared with the EGFR, indicating that this enzyme plays a major role in mediating the mitogenic effects of ALK in NIH 3T3 cells.

CD30-positive cutaneous T-cell lymphoma with concurrent solid tumour

Extranodal CD30+ T-cell lymphomas seldom carry classical t(2;5) translocation and are usually anaplastic large cell lymphoma kinase protein negative. They cover a wide spectrum of histological and clinical behaviour. The prognosis of CD30+ cutaneous T-cell lymphoma (CTCL) is good in the absence of nodal primary or disseminated disease. These lesions can undergo spontaneous regression, and overlap with the group of lesions of lymphomatoid papulosis. Although an increased incidence of solid tumours has been reported in patients with CD30+ non-Hodgkin lymphoma of the skin, reports of concurrent malignancies are rare in CD30+ CTCL. We report two patients with CD30+ CTCL who, respectively, had concurrent disseminated gastric carcinoma and bilateral ovarian teratoma. Despite an aggressive clinical and histological appearance, both cases ran favourable clinical courses. The CTCL responded completely to chemotherapy in one patient, who eventually succumbed to gastric cancer. In the other patient, lesions regressed spontaneously after bilateral oophorectomy. A possible relationship between the lymphoma and the solid tumours is discussed.

Tyrosine kinase oncogenes in normal hematopoiesis and hematological disease

Tyrosine kinase oncogenes are formed as a result of mutations that induce constitutive kinase activity. Many of these tyrosine kinase oncogenes that are derived from genes, such as c-Abl, c-Fes, Flt3, c-Fms, c-Kit and PDGFRbeta, that are normally involved in the regulation of hematopoiesis or hematopoietic cell function. Despite differences in structure, normal function, and subcellular location, many of the tyrosine kinase oncogenes signal through the same pathways, and typically enhance proliferation and prolong viability. They represent excellent potential drug targets, and it is likely that additional mutations will be identified in other kinases, their immediate downstream targets, or in proteins regulating their function.

Diversity of genomic breakpoints in TFG-ALK translocations in anaplastic large cell lymphomas: identification of a new TFG-ALK(XL) chimeric gene with transforming activity

Anaplastic large cell lymphomas are associated with chromosomal aberrations involving the anaplastic lymphoma kinase (ALK) gene at 2p23 that result in the expression of novel chimeric ALK proteins with transforming properties. In most of these tumors, the t(2;5)(p23;q35) generates the NPM-ALK fusion gene. However, several studies have now demonstrated that genes other than NPM may be fused to the ALK gene. We have recently described two different ALK rearrangements involving the TRK-fused gene (TFG) in which the same portion of ALK was fused to different length fragments of the 5' TFG region. These two rearrangements encoded chimeric proteins of 85 kd (TFG-ALK(S)) and 97 kd (TFG-ALK(L)), respectively. In this study, we have identified a new ALK rearrangement in which the catalytic domain of ALK was fused to a larger fragment of the TFG gene (TFG-ALK(XL)), encoding for a fusion protein of 113 kd. Genomic analysis of these three TFG-ALK rearrangements revealed that the TFG breakpoints occur at introns 3, 4, and 5, respectively, whereas the ALK breakpoints always occur in the same intron. No homologous regions or known recombination sequences were found in these regions. Transfection experiments using NIH-3T3 fibroblasts showed a similar transforming efficiency of TFG-ALK variants compared with NPM-ALK. In addition, in common with NPM-ALK, the TFG-ALK proteins formed stable complexes with the signaling proteins Grb2, Shc, and PLC-gamma. In conclusion, these findings indicate that the TFG may use a variety of intronic breakpoints in ALK rearrangements generating fusion proteins of different molecular weights, but with similar transforming potential than NPM-ALK.

Hodgkin's lymphoma: the pathologist's viewpoint

Despite its well known histological and clinical features, Hodgkin's lymphoma (HL) has recently been the object of intense research activity, leading to a better understanding of its phenotype, molecular characteristics, histogenesis, and possible mechanisms of lymphomagenesis. There is complete consensus on the B cell derivation of the tumour in most cases, and on the relevance of Epstein-Barr virus infection and defective cytokinesis in at least a proportion of patients. The REAL/WHO classification recognises a basic distinction between lymphocyte predominance HL (LP-HL) and classic HL (CHL), reflecting the differences in clinical presentation and behaviour, morphology, phenotype, and molecular features. CHL has been classified into four subtypes: lymphocyte rich, nodular sclerosing, with mixed cellularity, and lymphocyte depleted. The borders between CHL and anaplastic large cell lymphoma have become sharper, whereas those between LP-HL and T cell rich B cell lymphoma remain ill defined. Treatments adjusted to the pathobiological characteristics of the tumour in at risk patients have been proposed and are on the way to being applied.

Proteins encoded by genes involved in chromosomal alterations in lymphoma and leukemia: clinical value of their detection by immunocytochemistry

Acquired chromosomal anomalies (most commonly translocations) in lymphoma and leukemia usually result in either activation of a quiescent gene (by means of immunoglobulin or T-cell-receptor promotors) and expression of an intact protein product, or creation of a fusion gene encoding a chimeric protein. This review summarizes current immunocytochemical studies of these 2 categories of oncogenic protein, with emphasis on the clinical relevance of their detection in diagnostic samples. Among the quiescent genes activated by rearrangement, expression of cyclin D1 (due to rearrangement of the CCND1 [BCL-1] gene) is a near-specific marker of t(11;14) in mantle cell lymphoma; BCL-2 expression distinguishes follicular lymphoma cells from their nonneoplastic counterparts in reactive germinal centers and appears to be an independent prognostic marker in diffuse large cell lymphoma; and TAL-1 (SCL) expression identifies T-cell acute lymphoblastic neoplasms in which this gene is activated. The protein products of other genes activated by chromosomal rearrangement have a role as markers of either lineage (eg, PAX-5 [B-cell-specific activator protein] for B cells, including B-lymphoblastic neoplasms), or maturation stage (eg, BCL-6 for germinal-center and activated B cells and MUM-1/IRF4 for plasma cells). Currently, no hybrid protein encoded by fusion genes is reliably detectable by antibodies recognizing unique junctional epitopes (ie, epitopes absent from the wild-type constituent proteins). Nevertheless, staining for promyelocytic leukemia (PML) protein will detect acute PML with t(15;17) because the microspeckled nuclear labeling pattern for PML-RARalpha is highly distinctive. Similarly, antibodies to the anaplastic lymphoma kinase (ALK) tyrosine kinase are valuable (because wild-type ALK is not found in normal lymphoid tissue) in detecting neoplasms (CD30-positive large T-cell lymphomas) with t(2;5) or its variants. Thus, immunocytochemical detection of the products of many rearranged genes in lymphoma and leukemia can be clinically informative and provide information on cellular and subcellular protein expression that cannot be inferred from studies based on messenger RNA.

Multilevel dysregulation of STAT3 activation in anaplastic lymphoma kinase-positive T/null-cell lymphoma

Accumulating evidence indicates that expression of anaplastic lymphoma kinase (ALK), typically due to t(2;5) translocation, defines a distinct type of T/null-cell lymphoma (TCL). The resulting nucleophosmin (NPM) /ALK chimeric kinase is constitutively active and oncogenic. Downstream effector molecules triggered by NPM/ALK remain, however, largely unidentified. Here we report that NPM/ALK induces continuous activation of STAT3. STAT3 displayed tyrosine phosphorylation and DNA binding in all (four of four) ALK+ TCL cell lines tested. The activation of STAT3 was selective because none of the other known STATs was consistently tyrosine phosphorylated in these cell lines. In addition, malignant cells in tissue sections from all (10 of 10) ALK+ TCL patients expressed tyrosine-phosphorylated STAT3. Transfection of BaF3 cells with NPM/ALK resulted in tyrosine phosphorylation of STAT3. Furthermore, STAT3 was constitutively associated with NPM/ALK in the ALK+ TCL cell lines. Additional studies into the mechanisms of STAT3 activation revealed that the ALK+ TCL cells expressed a positive regulator of STAT3 activation, protein phosphatase 2A (PP2A), which was constitutively associated with STAT3. Treatment with the PP2A inhibitor calyculin A abrogated tyrosine phosphorylation of STAT3. Finally, ALK+ T cells failed to express a negative regulator of activated STAT3, protein inhibitor of activated STAT3. These data indicate that NPM/ALK activates STAT3 and that PP2A and lack of protein inhibitor of activated STAT3 may be important in maintaining STAT3 in the activated state in the ALK+ TCL cells. These results also suggest that activated STAT3, which is known to display oncogenic properties, as well as its regulatory molecules may represent attractive targets for novel therapies in ALK+ TCL.

MUC1 (EMA) is preferentially expressed by ALK positive anaplastic large cell lymphoma, in the normally glycosylated or only partly hypoglycosylated form

AIMS

To investigate whether MUC1 mucin, a high molecular weight transmembrane glycoprotein, also known as epithelial membrane antigen (EMA), differs in its expression and degree of glycosylation between anaplastic large cell lymphoma (ALCL) and classic Hodgkin's disease (HD), and whether MUC1 immunostaining can be used to differentiate between CD30 positive large cell lymphomas.

METHODS/RESULTS

Using five different monoclonal antibodies (E29/anti-EMA, DF3, 139H2, VU-4H5, and SM3) that distinguish between various MUC1 glycoforms, high MUC1 expression (50-95% of tumour cells positive) was found in 13 of 17 anaplastic lymphoma kinase (ALK) positive systemic nodal ALCLs, and in one of 20 cases of classic HD. Scattered or focal staining (< 25% of tumour cells) was seen in two additional ALK positive systemic ALCLs, two additional classic HD cases, and in three of 20 cases of ALK negative systemic nodal ALCL. Primary cutaneous ALCL showed no staining with the anti-MUC1 antibodies. Antibodies detecting hypoglycosylated MUC1 were found to be absent in all lymphomas (SM3) or present in only six of 15 ALK positive ALCLs (VU-4H5).

CONCLUSIONS

MUC1 is preferentially expressed by a subtype of systemic nodal ALCL, characterised by ALK expression, but is found in only a few cases of classic HD and ALK negative ALCL. Therefore, although MUC1 could be used in a panel of markers for CD30 positive lymphomas, it is probably not a valuable tool to differentiate between ALK negative CD30 positive large cell lymphomas. Finally, the degree of MUC1 glycosylation in lymphomas is relatively high, compared with the aberrant hypoglycosylation found in adenocarcinomas.

Expression of the oncogenic NPM-ALK chimeric protein in human lymphoid T-cells inhibits drug-induced, but not Fas-induced apoptosis

Anaplastic large cell lymphomas (ALCLs) are frequently associated with the t(2;5)(p23;q35) translocation, leading to the expression of NPM-ALK, a fusion protein linking nucleophosmin and anaplastic lymphoma kinase, a receptor tyrosine kinase. In ALCLs, dimerization of NPM-ALK leads to constitutive autophosphorylation and activation of the kinase, necessary for NPM-ALK oncogenicity. To investigate whether NPM-ALK, like other oncogenic tyrosine kinases, can inhibit drug-induced apoptosis, we permanently transfected NPM-ALK into Jurkat T-cells. As in ALCLs, NPM-ALK was expressed as a constitutively kinase-active 80 kDa protein, and could be detected by immunocytochemistry in nucleoli, nuclei and cytoplasm. Doxorubicin-induced apoptosis (assessed by cell morphology and annexin V-FITC binding) was significantly inhibited in two independent NPM-ALK-expressing clones (5.2+/-1.8 and 7.5+/-0.8% apoptosis), compared to control vector-transduced cells (36+/-6.7%). Similar results were observed with etoposide. In contrast, Fas-induced apoptosis was not inhibited. Cytochrome c release into the cytosol was delayed in doxorubicin-, but not anti-Fas-treated transfectant cells, indicating that apoptosis inhibition occurred upstream of mitochondrial events. Using NPM-ALK mutants, we demonstrated that inhibition of drug-induced apoptosis: (1) requires functional kinase activity, (2) does not involve phospholipase C-gamma, essential for NPM-ALK-mediated mitogenicity and (3) appears to be phosphoinositide 3-kinase independent, despite a strong Akt/PKB activation observed in wild type NPM-ALK-expressing cells. These results suggest that the NPM-ALK antiapoptotic and mitogenic pathways are distinct.

Hodgkin's lymphoma of T-cell type: clonal association with a CD30+ cutaneous lymphoma

The derivation of Reed-Sternberg cells in Hodgkin's lymphoma has been a subject of great interest. In most cases, Reed-Sternberg cells seem to be derived from germinal center B cells. In few sporadic cases, a T-cell origin has been shown. This article supports the concept of a T-cell derivation for rare cases of Hodgkin's lymphoma and provides evidence of a novel mechanism of pathogenesis from chronic inflammation in the skin.

Translocations involving anaplastic lymphoma kinase (ALK)

Anaplastic large-cell lymphoma (ALCL) comprises a group of non-Hodgkin's lymphomas (NHLs) that were first described in 1985 by Stein and co-workers and are characterized by the expression of the CD30/Ki-1 antigen (Stein et al., 1985). Approximately half of these lymphomas are associated with a typical chromosomal translocation, t(2;5)(p23;q35). Much confusion about the exact classification and clinicopathological features of this subgroup of NHL was clarified with the identification of NPM-ALK (nucleophosmin-anaplastic lymphoma kinase) as the oncogene created by the t(2;5) (Morris et al., 1994). With the discovery of NPM-ALK as the specific lymphoma gene mutation, this NHL subtype could be redefined on the molecular level. This achievement was enhanced by the availability of specific antibodies that recognize ALK fusion proteins in paraffin-embedded lymphoma tissues. Several excellent recent reviews have summarized the histopathological and molecular findings of ALCL and their use in the classification of this lymphoma entity (Anagnostopoulos and Stein, 2000; Benharroch et al., 1998; Drexler et al., 2000; Foss et al., 2000; Gogusev and Nezelof, 1998; Kadin and Morris, 1998; Ladanyi, 1997; Morris et al., 2001; Shiota and Mori, 1996; Skinnider et al., 1999; Stein et al., 2000). This review will focus on the molecular function and signal transduction pathways activated by ALK fusion oncogenes, with recent advances and possible clinical implications to be discussed.

Cutaneous manifestations of lymphoma: a clinical guide based on the WHO classification. World Health Organization

Cutaneous lymphomas are a heterogeneous group of lymphomas that show variations in histology, immunophenotype, and prognosis. At the time of presentation, cutaneous lymphomas may be primary or may involve the skin as a secondary site of involvement. Primary cutaneous lymphomas, in many instances, are distinct from morphologically similar lymphomas arising in lymph nodes. Their natural history is often more indolent than nodal lymphomas, and for that reason, they often require different therapeutic approaches. A classification scheme should recognize those lymphomas that are unique to the skin, as well as those arising in other sites. The mode of presentation of a lymphoma is often an indication of underlying biological distinctions. However, organ-specific classification systems undermine communication among medical specialists. The World Health Organization classification of hematopoietic and lymphoid malignancies offers a comprehensive approach and proposes that lymphomas should be viewed as a list of individual diseases and that each disease can be defined by a constellation of morphological, biological, and clinical features. The current review will focus on the spectrum of primary and secondary cutaneous lymphomas, emphasizing those features of importance to the clinical oncologist.

Prognostic significance of p80 and visceral involvement in childhood CD30 anaplastic large cell lymphoma (ALCL)

BACKGROUND

Between 1976 and 1998, CD30+anaplastic large cell lymphoma (ALCL) was diagnosed in 44 children (28 males, 16 females, age range 2.7-16.1 years, median 10). Up to 1993, 32 such children were treated according to a common chemotherapeutic protocol that stratified patients according to stage, without considering presenting features. Thereafter, patients presenting with visceral (lung, spleen, liver, gastro-intestinal tract) or mediastinal involvement were assigned to a high-risk treatment protocol with induction intensification. The generation of these two risk-groups was the result of a retrospective analysis of clinical risk factors for therapy failure as previously reported [Massimino M, Gasparini M, Giardini R, Ann Oncol 1995;6:915-920]. Considering the whole cohort of patients divided into group A-21/22 evaluable patients with visceral/mediastinal involvement, and group B-22 evaluable patients, with other ALCL location-disease-free survival (DFS) and survival (S) at 5 years were 57 and 58% for group A, and 83 and 100% (94% at 6 years) for group B, respectively.

PROCEDURE

We tested 15/21 cases of group A, and 18/22 of group B for p80 immunoreactivity in order to investigate a possible correlation between ALCL locations and NPM-ALK expression.

RESULTS

Thirteen of 15 specimens in group A and 17/18 in group B were positive for p80.

CONCLUSIONS

It is impossible to conclude anything about p80 positivity based on a series of 33/44 patients with childhood ALCL, neither about over-all prognosis nor about the role of visceral involvement. In adults, NPM-ALK protein expression is a favourable prognostic factor. Med Pediatr Oncol 2001;37:97-102.

Lymphoma immunophenotyping: a new era in paraffin-section immunohistochemistry

Recent advances in immunohistochemistry have made it possible to investigate lymphomas for the expression of a wide range of antigens in fixed tissues. Epitope retrieval, sensitive detection methods, and the availability of new monoclonal antibodies have all contributed to one's ability to perform detailed immunophenotyping that previously could only be done in cryostat sections or by flow cytometry. Current lymphoma classifications make use of characteristic immunophenotypic profiles that aid in the reproducible diagnosis and subcassification of these neoplasms. The following is a review of the current state of immunophenotyping for lymphoid neoplasms in fixed tissues.

Systemic anaplastic large-cell lymphoma: results from the non-Hodgkin's lymphoma classification project

Anaplastic large-cell lymphoma (ALCL) is a heterogeneous process that may have a T-cell, B-cell, or indeterminant (null) phenotype and which may or may not express the anaplastic lymphoma kinase (ALK) oncoprotein. Because the clinical significance of these variants of ALCL is unclear, we evaluated the cases of ALCL-T/null and ALCL-B identified in the Non-Hodgkin's Lymphoma Classification Project. We evaluated 1,378 cases of non-Hodgkin's lymphoma (NHL), and a consensus diagnosis of ALCL-T/null was made in 33 patients (2.4%) with a diagnostic accuracy of 85%. Compared to 96 patients with other forms of peripheral T-cell lymphoma (PTCL), those with ALCL-T/null were significantly younger, less likely to have advanced-stage disease or bone marrow involvement, more likely to have a low International Prognostic Index score, and had a significantly better survival. Among those with ALCL-T/null, there were no significant differences in the clinical features or survival on the basis of ALK expression. A consensus diagnosis of ALCL-B was made in 15 patients (1.1%), and the diagnostic accuracy was 67%. However, compared to 366 patients with other forms of diffuse large B-cell lymphoma (DLBCL), those with ALCL-B were no different with regard to clinical features or survival. We conclude that patients with ALCL-T/null have favorable prognostic features and excellent survival and should be separated from those with other forms of PTCL for prognostic and therapeutic purposes. In contrast, patients with ALCL-B appear to be similar to those with other forms of DLBCL.

The NPM-ALK and the ATIC-ALK fusion genes can be detected in non-neoplastic cells

Anaplastic large cell lymphoma (ALCL) is frequently associated with the t(2;5)(p23;q35) translocation. It creates a NPM-ALK fusion gene, fusing the anaplastic lymphoma kinase (ALK) gene (2p23) and the nucleophosmin (NPM) gene (5q35). Other rearrangements involving the ALK gene have recently been shown to be associated with ALCL, among which the ATIC-ALK rearrangement resulting from the inv(2)(p23q35) translocation is probably the most recurrent. The aims of the present study were to investigate the presence of NPM-ALK and ATIC-ALK fusion genes in ALCL, using a real-time 5' exonuclease-based reverse-transcription polymerase chain reaction (RT-PCR). This sensitive technique was also applied to investigate whether both fusion genes might be detected in Hodgkin's disease cases and in reactive lymphoid tissue. Results of the RT-PCR were compared to ALK immunostaining, cytogenetics, and fluorescence in situ hybridization (FISH) results. RT-PCR detected the NPM-ALK and ATIC-ALK fusions at high levels in 8 and 3 of a total of 13 ALK-positive ALCL cases. One ALK-positive ALCL case was negative for both fusion genes analyzed but revealed a new ALK-related translocation t(2;17)(p23;q25) by cytogenetic and FISH analysis. In addition, of the eight ALK-positive ALCL cases that were strongly positive for the NPM-ALK fusion, three cases also showed the presence of the ATIC-ALK fusion, although at much lower levels. Similarly, out of the three strongly positive ATIC-ALK cases, one case was positive for the NPM-ALK fusion, at low levels. Finally, the NPM-ALK and the ATIC-ALK fusions were detected, at equally low levels, respectively in 13 and 5 ALK-negative ALCL cases, in 11 and 5 Hodgkin's disease cases and in 20 and 1 non-neoplastic lymphoid tissues. The distinction between the high- and low-level detection was confirmed by relative quantitative RT-PCR for a representative number of cases. Of interest is the fact that the high-level detection coincided with the presence of ALK gene rearrangement detected by cytogenetics and FISH and may reflect a central role of the transcript in the oncogenic mechanism of ALK-positive ALCL. Low-level detection is not supported by cytogenetics and FISH, presumably due to the presence of the transcripts in only a small minority of normal cells not detectable by these techniques. Our findings demonstrate that NPM-ALK and ATIC-ALK fusion transcripts may be detected in conditions other than ALK-positive ALCL including reactive lymphoid tissues, although at low levels, suggesting the presence of the transcripts in normal (bystander) cells. Moreover, they suggest that the ALK gene rearrangement by itself might be insufficient to induce tumor formation. They further question the validity of quantitative real-time RT-PCR for monitoring minimal residual disease in ALCL. Finally, the newly identified translocation t(2;17)(p23;q25) can be added to the list of ALK gene rearrangements occurring in ALK-positive ALCL.

Anaplastic lymphoma kinase expression in inflammatory pseudotumors

Anaplastic lymphoma kinase (ALK), a hallmark of anaplastic large cell lymphoma, has recently been implicated in the genesis of some inflammatory pseudotumors (inflammatory myofibroblastic tumors) in children and young adults. The aim of this study was to determine the frequency of its expression among inflammatory pseudotumors, and to characterize the clinicopathologic features of the positive cases. Sixty-one cases of inflammatory pseudotumors were retrieved from the surgical pathology archives and consultation files. Paraffin sections were immunostained with the antibody ALK1. The patients ranged in age from 0.5 to 79 years (median age, 50 years), with 10 patients (16.4%) younger than 20 years. Five cases (8.2%) were ALK+, including two of six urogenital inflammatory myofibroblastic tumors, none of eight pulmonary inflammatory pseudotumors, three (one adrenal, one small bowel, one liver) of 31 extrapulmonary inflammatory pseudotumors, none of nine hepatic/splenic inflammatory pseudotumors expressing follicular dendritic cell markers and harboring Epstein-Barr virus, and none of seven inflammatory pseudotumors of the lymph node. When only those patients 40 years or younger were considered, the ALK positivity rate became 21.7% (five of 23). All five ALK+ cases occurred in young patients aged 0.5 to 37 years, who were alive and well at 3.5 to 17 years. The tumors exhibited a spectrum of histologic features typical of inflammatory pseudotumors/myofibroblastic tumors, but there was at least focal nuclear atypia. Immunostaining for ALK produced fibrillary or granular cytoplasmic staining in the neoplastic cells, sometimes with cell membrane accentuation. This study confirms that ALK is implicated in a proportion of inflammatory pseudotumors, and is generally associated with a favorable outcome. The results also support the heterogeneity of inflammatory pseudotumors, with the follicular dendritic cell/Epstein-Barr virus-positive cases and those occurring in lymph nodes representing different biologic entities.

Primary systemic anaplastic large-cell lymphoma (CD30+): advances in biology and current therapeutic approaches

In 1985, Stein et al demonstrated the expression of the lymphoid activation antigen CD30/Ki by neoplastic cells. Fifteen years after the first description, anaplastic large-cell lymphomas (ALCL) are now thought to be a heterogeneous group in terms of their clinical, morphologic, phenotypic, cytogenetic, and molecular biology features. However, on the basis of a specific genetic anomaly and expression of a chimeric nucleophosmin anaplastic lymphoma kinase (NPM-ALK) protein and its variants, a distinct clinicopathologic entity defined as "ALK-positive lymphoma" or "ALKoma" can be recognized. Based on molecular and clinical criteria, 3 entities of primary ALCL can be identified: primary systemic ALK positive, primary systemic ALK negative, and primary cutaneous ALCL. This review focuses on advances in the knowledge of primary systemic ALCL biology and discusses therapeutic approaches based on ALK expression. The presence of this protein appears to be an important prognostic factor and, combined with an age-adjusted International Prognostic Index, could allow researchers to design more specific clinical trials aimed at finding new, more efficacious and less toxic treatments.

ALK1 and p80 expression and chromosomal rearrangements involving 2p23 in inflammatory myofibroblastic tumor

BACKGROUND

Inflammatory myofibroblastic tumor (IMT) is an uncommon tumor of extrapulmonary and pulmonary tissues with an unpredictable clinical course, occasional recurrences, and rare malignant transformation. Clonal abnormalities with rearrangements of chromosome of 2p23 and the ALK gene have been reported in a few cases. The purpose of this study is to investigate whether these are consistent abnormalities among IMTs or represent a distinct subset.

DESIGN

Formalin-fixed, paraffin-embedded archival tissue sections from 47 IMTs in 40 patients were immunostained with monoclonal antibodies against ALK and p80. Fluorescence in situ hybridization for ALK rearrangements was done on 22 IMTs from 19 patients. Findings were correlated with clinical features and outcome.

RESULTS

ALK positivity was observed in 17 of 47 IMTs (36%) and p80 positivity in 16 of 47 IMTs (34%). Fluorescence in situ hybridization showed ALK rearrangements in nine cases (47%), aneuploidy in three cases (16%), and no rearrangement in seven cases (37%). IMTs with ALK abnormalities by immunohistochemistry and/or fluorescence in situ hybridization originated in the abdomen/pelvis/retroperitoneum, chest, and extremities. The mean age was 6.6 years, with a male/female ratio of 1.3. 64% of patients had no evidence of disease at last follow-up, 45% had one or more recurrences, and 18% displayed histologic evidence of malignant transformation. The IMTs without ALK abnormalities occurred in older children, were more frequent in females, and had fewer recurrences. However, in this group of 40 patients, the differences between the groups with and without ALK abnormalities did not have statistical significance. Aneuploidy without ALK abnormalities was associated with malignant transformation in three of five cases.

CONCLUSIONS

Abnormalities of ALK and p80 and evidence of chromosomal rearrangements of 2p23 occur in a significant proportion of IMTs. These changes are most frequent in abdominal and pulmonary IMTs in the first decade of life and are associated with a higher frequency of recurrence. These findings confirm the neoplastic nature of a subset IMT with ALK abnormalities and suggest that aneuploid IMT is a subset with more aggressive clinical behavior.

Involvement of 2p23 in pulmonary inflammatory pseudotumors

Pulmonary inflammatory pseudotumors (IP) are rare mesenchymal proliferations that have a polymorphic histology and an unpredictable biologic behavior. The histologic spectrum of IP has led to uncertainty as to whether this tumor has a reactive or neoplastic pathogenesis. Reports of extrapulmonary IP have identified clonal chromosomal aberrations involving 2p23 in the region of the ALK gene. Using fluorescence in situ hybridization with a probe flanking the ALK gene at 2p23 and immunostaining for the ALK gene product, we studied formalin-fixed, paraffin-embedded tissues of pulmonary IP and found a subset (33%) with 2p23 aberrations. We suggest that chromosomal rearrangements and ALK immunostaining may be helpful in the diagnosis of a group of pulmonary IP and should be investigated as a potential tool for predicting their future biologic behavior. An association with anaplastic large-cell lymphoma was also observed. HUM PATHOL 32:428-433.

Peripheral T/NK-cell lymphoma: a report of the IXth Workshop of the European Association for Haematopathology

AIMS

In April 1998, The European Association for Haematopathology organized the IXth workshop on peripheral T-cell and NK-cell lymphomas and leukaemias. The workshop focused on unusual subtypes of these rare malignancies, allowing evaluation of the recently published WHO classification of neoplastic diseases of the lymphoid tissues.

METHODS AND RESULTS

One-hundred and three cases were centrally immunophenotyped and hybridized for EBER1/2 of Epstein--Barr virus. All cases were reviewed by a panel of experienced haematopathologists and classified according to the new WHO classification for lymphoid neoplasms. Three cases were considered as precursor T-cell and 95 cases as peripheral T/NK-cell lymphoma/leukaemia. Although the cases represented a selected series of unusual cases, the following conclusions could be made: (i) Most lymphomas except the hepatosplenic gamma/delta T-cell lymphomas showed a rather broad morphological spectrum, with differences both between and within individual tumours. (ii) This heterogeneity was also reflected by the immunophenotype, for instance a variable expression of CD30 was found in many enteropathy type T-cell lymphomas. (iii) Exceptions in phenotype were regularly found in almost all categories, indicating that phenotype should not be the final determining factor in classification. (iv) The great majority of T-cell lymphomas expressed the alpha/beta T-cell receptor, with the exception of all but one hepatosplenic T-cell lymphomas and a few other extranodal peripheral T cell lymphomas. (v) Malignancies of precursor cells, blastic NK-cell lymphoma/leukaemia, adult T-cell lymphoma/leukaemia and most AIL-type T-cell lymphomas did not express cytotoxic molecules such as TIA1 and granzyme-B. In contrast, all five aggressive NK/T-cell lymphomas/leukaemias, a single case of large granular lymphocyte leukaemia and 40 of 47 primary extranodal lymphoma/leukaemias expressed these molecules. In hepatosplenic gamma/delta T-cell lymphoma, five of six cases showed expression of TIA1 but not of granzyme-B. (vi) Seven tumours developed after organ-transplant, four cases being EBV-positive. No distinct phenotype could be attributed to these cases.

CONCLUSIONS

Most peripheral T/NK cell lymphomas could be categorized as distinct entities as described in the recently proposed WHO classification for lymphoid neoplasms.

Molecular characterization of a new ALK translocation involving moesin (MSN-ALK) in anaplastic large cell lymphoma

The majority of anaplastic large cell lymphomas (ALCL) are associated with chromosomal abnormalities affecting the anaplastic lymphoma kinase (ALK) gene which result in the expression of hybrid ALK fusion proteins in the tumor cells. In most of these tumors, the hybrid gene comprises the 5' region of nucleophosmin (NPM) fused in frame to the 3' portion of ALK, resulting in the expression of the chimeric oncogenic tyrosine kinase NPM-ALK. However, other variant rearrangements have been described in which ALK fuses to a partner other than NPM. Here we have identified the moesin (MSN) gene at Xq11-12 as a new partner of ALK in a case of ALCL which exhibited a distinctive membrane-restricted pattern of ALK labeling. The hybrid MSN-ALK protein had a molecular weight of 125 kd and contained an active tyrosine kinase domain. The unique membrane staining pattern of ALK is presumed to reflect association of moesin with cell membrane proteins. In contrast to other translocations involving the ALK gene, the ALK breakpoint in this case occurred within the exonic sequence coding for the juxtamembrane portion of ALK. Identification of the genomic breakpoint confirmed the in-frame fusion of the whole MSN intron 10 to a 17 bp shorter juxtamembrane exon of ALK. The breakpoint in der(2) chromosome showed a deletion, including 30 bp of ALK and 36 bp of MSN genes. These findings indicate that MSN may act as an alternative fusion partner for activation of ALK in ALCL and provide further evidence that oncogenic activation of ALK may occur at different intracellular locations.

Anaplastic large cell lymphoma: the shifting sands of diagnostic hematopathology

Anaplastic large cell lymphoma (ALCL) is a paradigm for the process used to define new disease entities, and provides a model that is applicable to all areas of pathology. ALCL was first recognized based on characteristic histologic features (sinusoidal invasion) and a distinctive immunophenotype (CD30+). However, neither sinusoidal invasion nor CD30-positivity proved to be entirely specific. Subsequently, a characteristic cytogenetic abnormality was identified, the t(2;5), that led to identification of the genes involved in the translocation (NPM/ALK) and insights into the pathogenesis. Generation of monoclonal antibodies to the aberrantly expressed anaplastic large cell lymphoma kinase (ALK) such as ALK-1 can be used diagnostically, and have led to improved definition of the diagnostic entity with important clinical and prognostic implications. These studies also have clarified the relationship of ALCL to Hodgkin's disease, another lymphoid malignancy associated with CD30 expression. We have learned that the ultimate histologic spectrum of ALCL is both narrower and broader than originally believed. The small cell and lymphohistiocytic variants of ALCL are ALK-positive, and are an accepted part of the disease entity, although the neoplastic cells may appear neither large nor anaplastic. Conversely, most cases of Hodgkin's-like ALCL have proved to be more closely related to true Hodgkin's disease, and are unrelated to ALCL.

Morphological and phenotypic features in pediatric large cell lymphoma and their correlation with ALK expression and the t(2;5)(p23;q35) translocation

Anaplastic large cell lymphoma (ALCL) was proposed as a clinicopathologic entity over 14 years ago, but has been somewhat controversial due to the variability of its defining features and variable occurrence in different age-groups. To evaluate this entity in a pediatric population, 36 cases of childhood large cell lymphoma were evaluated for abnormalities of the anaplastic lymphoma kinase (ALK) gene that has been associated with ALCL morphology and immunophenotype. ALK abnormalities were evaluated by assay for the t(2;5)(p23;q35) translocation by RT-PCR and/or expression of NPM-ALK fusion protein by immunohistochemistry. Results showed 17 patients to have evidence of ALK gene expression. All of these children (mean age, 9.3 years) had tumors that were of T-cell phenotype (with the exception of a single case of null phenotype) and that expressed CD30. In contrast, 19 children with no evidence of ALK expression were older (mean, 12.7 years), and the majority (12/19) had tumors of B-cell phenotype. CD30 was also diffusely expressed in 8 of these 19 tumors. The difference in mean age between the two groups was statistically significant (P = 0.015). In three cases tested for both ALK and the t(2;5), ALK protein was detected in the absence of the t(2;5) translocation but no cases showed the reverse pattern, consistent with ALK fusion to genes other than NPM or activation of the ALK gene by another mechanism. These findings provide further support that ALK-positive ALCL is a distinct pathologic entity among pediatric large cell lymphomas primarily characterized by expression of T-cell markers, CD30, and EMA, and by a younger mean age.

Percentage of activated cytotoxic T-lymphocytes in anaplastic large cell lymphoma and Hodgkin's disease: an independent biological prognostic marker

Recently, we demonstrated that the presence of high percentages of activated cytotoxic T-lymphocytes (CTLs) in biopsy specimens of both Hodgkin's disease (HD) and ALK negative anaplastic large cell lymphoma (ALCL) is associated with a poor prognosis. To test whether this biological prognostic factor is more important in predicting clinical outcome than histological diagnosis or clinical factors, we compared the prognostic value of these parameters in an expanded group of classical HD and ALK negative ALCL. Tumor biopsies of classical HD (n = 83) and ALK negative systemic nodal ALCL (n = 43) were investigated for the presence of activated CTLs by immunohistochemistry, using a monoclonal antibody directed against granzyme B. Percentages of activated CTLs were quantified using Q-PRODIT, and their prognostic value was compared to that of histological diagnosis and clinical parameters, including age and stage. Both in classical HD and ALK negative ALCL, a high percentage of activated CTLs (ie > or = 15%) identified a group of patients with poor overall and progression-free survival time, even when adjusted for stage. In multivariate analysis, percentage of activated CTLs remained a strong independent prognostic marker, and was more sensitive than histological diagnosis or clinical factors in predicting overall survival time. We conclude that a high percentage of activated CTLs in the reactive infiltrate of ALK negative ALCL and classical HD is a strong indicator for an unfavorable clinical outcome, regardless of histological diagnosis or clinical parameters. As such, this biological parameter may be an especially helpful tool to determine therapeutic strategies in cases in which the differentiation between ALK negative ALCL and HD remains difficult.

Timely topic: anaplastic lymphoma kinase (ALK) spreads its influence

Anaplastic lymphoma kinase (ALK) is normally not expressed in human tissues except selected sites in the nervous system. Its expression and constitutive activation as a result of a chromosomal translocation involving 2p23 plays a pivotal role in the genesis of anaplastic large cell lymphoma. ALK expression has been instrumental in defining a homogeneous subset from the category of anaplastic large cell lymphoma, characterised by occurrence in young patients, primary systemic presentation, favorable prognosis, a broad morphological spectrum, nuclear and/or cytoplasmic immunostaining for ALK protein, and a number of possible fusion partner genes such as NPM, ATIC, TFG, TPM3 and CLTCL. Recently ALK has been implicated in the genesis of another tumour type, the inflammatory myofibroblastic tumours. The ALK-positive examples occur in children and young adults, involving a variety of sites, such as the abdomen, mesentery, liver, bladder, mediastinum, lung and bone. The partner genes identified in some cases are TPM3 (tropomyosin 3) and TPM4 (tropomyosin 4). These molecular findings also further support the neoplastic nature of at least a subset of inflammatory myofibroblastic tumours.

T Cell and NK Cell Lymphoproliferative Disorders

This review covers the diagnosis and management of natural killer and peripheral T-cell lymphomas (PTCL). Problems with PTCL include their rarity, representing usually 10-15% of non-Hodgkin's lymphomas in the Western Hemisphere, morphologic heterogeneity, and lack of immunophenotypic markers for clonality. Additionally, their clinical behavior is variable and may not correlate with morphology.

Dr. Kinney gives a general overview of the diagnosis of PTCL and NK cell neoplasms. Emphasis will be placed on extranodal T cell and natural killer (NK) cell lymphomas such as hepatosplenic lymphoma, subcutaneous panniculitis-like lymphoma and nasal/nasal type T/NK-cell lymphoma. The use of ALK gene regulation in the classification of anaplastic large cell lymphoma is also reviewed.

Dr. Loughran describes current understanding of the pathogenesis of large granular lymphocyte (LGL) leukemia. The discussion focuses on LGL leukemia as an instructive model of dysregulated apoptosis causing both malignant and autoimmune disease. Current management options and mechanisms of therapeutic response are also described.

Dr. Greer addresses whether PTCL should be treated differently from the more common diffuse large B cell lymphomas. He discusses the therapeutic options for anaplastic large cell lymphoma (ALCL), from a conservative approach for primary cutaneous ALCL to combination chemotherapy for the highly chemosensitive ALCL expressing anaplastic lymphoma kinase. He reviews therapy options for the extranodal subtypes of PTCL by drawing from series in adults, pediatrics, dermatology, and the Far East.

CD30+ anaplastic large cell lymphoma: a review of its histopathologic, genetic, and clinical features

Anaplastic large cell lymphoma (ALCL) represents a generally recognized group of large cell lymphomas. Defining features consist of a proliferation of predominantly large lymphoid cells with strong expression of the cytokine receptor CD30 and a characteristic growth pattern. With the use of molecular and clinical criteria, 3 entities of ALCL have been identified: primary systemic anaplastic lymphoma kinase (ALK)+ ALCL, primary systemic ALK− ALCL, and primary cutaneous ALCL. ALK expression is caused by chromosomal translocations, most commonly t(2;5). ALK+ ALCL predominantly affects young male patients and, if treated with chemotherapy, has a favorable prognosis. It shows a broad morphologic spectrum, with the “common type,” the small cell variant, and the lymphohistiocytic variant being most commonly observed. The knowledge of the existence of these variants is essential in establishing a correct diagnosis. ALK− ALCL occurs in older patients, affecting both genders equally and having an unfavorable prognosis. The morphology and the immunophenotype of primary cutaneous ALCL show an overlap with that of lymphomatoid papulosis. Both diseases have an excellent prognosis, and secondary systemic dissemination is only rarely observed. The described ALCL entities usually derive from cytotoxic T cells. In contrast, large B-cell lymphomas with anaplastic morphology are believed to represent not a separate entity but a morphologic variant of diffuse large B-cell lymphoma. Malignant lymphomas with morphologic features of both Hodgkin disease and ALCL have formerly been classified as Hodgkin-like ALCL . Recent immunohistologic studies, however, suggest that ALCLs Hodgkin-like represent either cases of tumor cell–rich classic Hodgkin disease or (less commonly) ALK+ ALCL or ALK− ALCL.