A New Subtype of Large B-Cell Lymphoma Expressing the ALK Kinase and Lacking the 2; 5 Translocation

ALK-positive diffuse large B-cell lymphoma of the duodenum: A case report and review of the literature

Anaplastic lymphoma kinase (ALK)-positive diffuse large B-cell lymphoma (ALK⁺ DLBCL) is characterized by the presence of immunoblastic or plasmablastic cells with a strong ALK protein expression that is frequently associated with t(2;17)(p23;q23). The present study reports a case of ALK⁺ DLBCL in a 26-year-old male with a duodenal mass. Histologically, the neoplastic cells demonstrated prominent plasmablastic differentiation with abundant amphophilic cytoplasma and central nucleoli. Paraffin immunohistochemistry revealed: an exclusively cytoplasmic granular expression of ALK; CD138, immunoglobulin A (IgA) and CD79α positivity; and focal expression of multiple myeloma oncogene 1 (Mum-1), CD30 and epithelial membrane antigen (EMA). However, the immunohistochemical staining was negative for CD3, CD38 and CD20. Fluorescence in situ hybridization (FISH) analysis using an ALK break-apart probe revealed the presence of ALK gene rearrangements in the patient. To the best of our knowledge, the current case represents the first example of primary extranodal ALK⁺ DLBCL presenting as a duodenal mass.

Anaplastic lymphoma kinase-positive large B-cell lymphoma: description of a case with an unexpected clinical outcome

Anaplastic lymphoma kinase-positive (ALK-positive) large B-cell lymphoma is a rare and aggressive variant of large B-cell lymphoma (LBCL), first reported by Delsol et al in 1997, showing distinctive morphologic, immunophenotypic and cytogenetic features. The latest 2008 World Health Organization Classification of Tumours of Haematopoietic and Lymphoid tissues recognizes ALK-positive LBCL as a separate entity. Here, we report a case of ALK-positive large B-cell lymphoma in a 53-year-old man with diffuse abdominal and mediastinal lymph-nodes involvement. According to the Ann Arbor staging system, the patient had a stage IIIB lymphoma. The age-adjusted International Prognostic Index was 2 (stage III and elevated lactate dehydrogenase), so the disease was considered high risk. The patient underwent chemotherapy, radiotherapy, and an autologous stem cell transplantation. The patient is alive and free of disease 35 months after diagnosis.

ALK as a paradigm of oncogenic promiscuity: different mechanisms of activation and different fusion partners drive tumors of different lineages

Anaplastic lymphoma kinase (ALK) is a receptor tyrosine kinase protein implicated in a variety of hematological malignancies and solid tumors. Since the identification of the ALK gene in 1994 as the target of the t(2;5) chromosomal translocation in anaplastic large cell lymphoma, ALK has been proven a remarkably promiscuous oncogene. ALK contributes to the development of a notable assortment of tumor types from different lineages, including hematolymphoid, mesenchymal, epithelial and neural tumors, through a variety of genetic mechanisms: gene fusions, activating point mutations, and gene amplification. Recent developments led to significant diagnostic and therapeutic advances, including efficient diagnostic tests and ALK-targeting agents readily available in the clinical setting. This review addresses some therapeutic considerations of ALK-targeted agents and the biologic implications of ALK oncogenic promiscuity, but the main points discussed are: 1) the variety of mechanisms that result in activation of the ALK oncogene, with emphasis on the promiscuous partnerships demonstrated in chromosomal rearrangements; 2) the diversity of tumor types of different lineages in which ALK has been implicated as a pathogenic driver; and 3) the different diagnostic tests available to identify ALK-driven tumors, and their respective indications.

ALK-positive large B-cell lymphomas express a terminal B-cell differentiation program and activated STAT3 but lack MYC rearrangements

ALK-positive large B-cell lymphoma is an aggressive lymphoid neoplasm characterized by a monomorphic proliferation of immunoblast-like cells expressing a plasmablastic phenotype and carrying ALK rearrangements. MYC rearrangements are frequent in plasmablastic lymphomas, advanced plasma cell myelomas and a subgroup of diffuse large B-cell lymphomas, but their presence in ALK-positive large B-cell lymphomas is unknown. MYC expression is downregulated by BLIMP1, a master modulator of plasma cell differentiation. BLIMP1 and MYC are upregulated by STAT3, a signal transducer activated by ALK. To determine the role of BLIMP1, MYC and STAT3 in the pathogenesis of ALK-positive large B-cell lymphomas, we investigated MYC rearrangement and the expression of MYC, phosphorylated STAT3, BLIMP1, PAX5 and XBP1 in 12 ALK-positive large B-cell lymphomas. All cases expressed ALK with a granular cytoplasmic pattern. Nine cases had a split signal consistent with an ALK rearrangement. Three additional cases showed a deletion of the 5' or 3' end of the ALK probe consistent with cryptic translocation. PAX5 was virtually negative in all cases tested, whereas BLIMP1 was expressed in all tumors and XBP1 in 11 of 12. Phosphorylated STAT3 was observed in all cases with a strong and diffuse nuclear pattern. MYC rearrangements were not identified in any tumor, but MYC gains and amplification were detected in six cases and one case, respectively. MYC protein was expressed in all tumors independently of MYC gene alterations. These results indicate that ALK-positive large B-cell lymphomas express a complete plasmablastic differentiation program but, contrary to plasmablastic lymphomas, do not have MYC rearrangements. STAT3 is constantly activated and may be an alternative mechanism to promote MYC expression in these tumors. The relevance of the ALK/STAT3 pathway in the pathogenesis of ALK-positive large B-cell lymphomas may offer an attractive target for new therapies.

Anaplastic lymphoma kinase (ALK1) immunohistochemistry in diagnostic dermatopathology; an update

The use of anaplastic lymphoma kinase antibodies (ALK1) as a diagnostic aid has expanded since becoming a routinely available immunohistochemical stain. Because the skin may be the site of a wide variety of hematolymphoid and fibroblastic proliferations, dermatopathologists commonly use ALK1 as part of a broader staining panel in diagnosing soft tissue and cutaneous hematolymphoid neoplasms. Furthermore, new entities and differential diagnostic contexts are emerging, which broaden the utility of ALK1 immunohistochemistry. We review the expanding role of ALK1 immunohistochemistry in contemporary dermatopathology.

The histological and biological spectrum of diffuse large B-cell lymphoma in the World Health Organization classification

Diffuse large B-cell lymphomas (DLBCLs) are aggressive B-cell lymphomas that are clinically, pathologically, and genetically diverse, in part reflecting the functional diversity of the B-cell system. The focus in recent years has been toward incorporation of clinical features, morphology, immunohistochemistry, and ever evolving genetic data into the classification scheme. The 2008 World Health Organization classification reflects this complexity with the addition of several new entities and variants. The discovery of distinct subtypes by gene expression profiling heralded a new era with a focus on pathways of transformation as well as a promise of more targeted therapies, directed at specific pathways. Some DLBCLs exhibit unique clinical characteristics with a predilection for specific anatomic sites; the anatomic site often reflects underlying biological distinctions. Recently, the spectrum of Epstein-Barr virus (EBV)-driven B-cell proliferations in patients without iatrogenic or congenital immunosuppression has been better characterized; most of these occur in patients of advanced age and include Epstein-Barr virus (EBV)-positive large B-cell lymphoma of the elderly. Human herpesvirus 8 is involved in the pathogenesis of primary effusion lymphoma, which can present as a "solid variant." Two borderline categories were created; one deals with tumors at the interface between classic Hodgkin lymphoma and DLBCL. The second confronts the interface between Burkitt lymphoma and DLBCL, so-called "B-cell lymphoma, unclassifiable, with features intermediate between DLBCL and Burkitt lymphoma" in the 2008 classification. Most cases harbor both MYC and BCL2 translocations and are highly aggressive. Another interesting entity is anaplastic lymphoma kinase-positive DLBCL, which renders itself potentially targetable by anaplastic lymphoma kinase inhibitors. Ongoing investigations at the genomic level, with both exome and whole-genome sequencing, are sure to reveal new pathways of transformation in the future.

30 years of lymph node pathology: biomarkers and other advances

Over the last 30 years there has been a massive change in both the clinical and pathologic aspects of malignant lymphomas. Pathologists are now able to evaluate cellular phenotypes and lineages of tumor cells using a wide variety of biomarkers and molecular techniques. The ability to identify tumor cell phenotypes has revolutionized the classification of lymphomas, leading to an internationally agreed system based on the reliable recognition of specific clinico-pathologic entities. The World Health Organization classification combines clinical features, histomorphology, immunohistochemistry, and molecular and genetic marker data to precisely categorize lymphomas. On the clinical front the increasing use of needle core biopsies has made it easier and quicker to obtain tissue samples, and the development of (18)F-fluorodeoxyglucose positron emission tomography has revolutionized the assessment of patients both at presentation and after treatment. To improve overall outcomes for lymphoma patients there have been advances in the UK organization of cancer services. Cancer networks have been established, often with network multidisciplinary team meetings, and new diagnoses of lymphoma are reviewed on a network basis by pathologists specializing in the field. National and supranational quality control systems are in place for immunohistochemistry and for molecular techniques and multicenter clinical trials provide information about the efficacy of treatment regimens. The outcome of these advances is that a patient presenting in 2012 with suspected lymphoma can expect to be biopsied rapidly, to receive an accurate pathologic diagnosis by an expert hematopathologist, which will include prognostic marker information, and to have comprehensive disease assessment and discussion by a multidisciplinary team before embarking on the most appropriate treatment for his or her clinical situation.

Anaplastic lymphoma kinase as a therapeutic target

INTRODUCTION

Anaplastic lymphoma kinase (ALK), a tyrosine kinase receptor, has been initially identified through its involvement in chromosomal translocations associated with anaplastic large cell lymphoma. However, recent evidence that aberrant ALK activity is also involved in an expanding number of tumor types, such as other lymphomas, inflammatory myofibroblastic tumor, neuroblastomas and some carcinomas, including non-small cell lung carcinomas, is boosting research progress in ALK-targeted therapies.

AREAS COVERED

The first aim of this review is to describe current understandings about the ALK tyrosine kinase and its implication in the oncogenesis of human cancers as a fusion protein or through mutations. The second goal is to discuss its interest as a therapeutic target and to provide a review of the literature regarding ALK inhibitors. Mechanisms of acquired resistance are also reviewed.

EXPERT OPINION

Several ALK inhibitors have recently been developed, offering new treatment options in tumors driven by abnormal ALK signaling. However, as observed with other tyrosine kinase inhibitors, resistance has emerged in patients treated with these agents. The complexity of mechanisms of acquired resistance recently described suggests that other therapeutic options, including combination of ALK and other kinases targeted drugs, will be required in the future.

Targeting ALK: a promising strategy for the treatment of non-small cell lung cancer, non-Hodgkin's lymphoma, and neuroblastoma

Anaplastic lymphoma kinase (ALK) is a tyrosine kinase receptor that affects a number of biological and biochemical functions through normal ligand-dependent signaling. It has oncogenic functions in a number of tumors including non-small cell lung cancer (NSCLC), anaplastic large cell lymphoma, and neuroblastoma when altered by translocation or amplification or mutation. On August 2011, a small molecule inhibitor against ALK, crizotinib, was approved for therapy against NSCLC with ALK translocations. As we determine the molecular heterogeneity of tumors, the potential of ALK as a relevant therapeutic target in a number of malignancies has become apparent. This review will discuss some of the tumor types with oncogenic ALK alterations. The activity and unique toxicities of crizotinib are described, along with potential mechanisms of resistance and new therapies beyond crizotinib.

Diagnostic Impact of Molecular Lineage Analysis on Paraffin-Embedded Tissue in Hematolymphoid Neoplasia Reclassified by Current WHO Criteria

BACKGROUND AND OBJECTIVE

By current WHO criteria, most - though not all - cases of hematolymphoid neoplasm can be diagnosed immunomorphologically, diminishing the role of molecular tests for lymphoid antigen receptor clonality in lymphoma diagnosis. Hence, our objective was to glean immunomorphological and molecular correlates from hematolymphoid neoplasms that had remained unresolvable without diagnostic molecular input.

METHODS

Thirty-five such cases were reviewed histologically and with standard immunoperoxidases. In situ hybridization for Epstein-Barr virus (EBV)-encoded RNAs (EBER) was performed on selected cases. PCR amplification of genes encoding T-cell receptors (TcR) and immunoglobulin heavy chains (IgH) [TR and IGH genes, respectively] was performed on whole tissue in all cases, and on microdissected cells in two cases.

RESULTS

Twenty-five cases (71%) requiring diagnostic molecular genotyping had some form of peripheral T-cell lymphoma (PTCL). Twenty (80%) of these were complicated by a proliferation of B-lineage cells, either within the same tissue ('syntopic') as large B cells (LBC) or Reed-Sternberg (RS)-like cells (17 cases), florid lymphoid hyperplasia (two cases, one also with syntopic LBC) or monotypic plasma cells (one case), or at a separate ('metatopic') site as a B-cell lymphoma (two cases, one of which also had syntopic LBC) or Hodgkin lymphoma (HL; one case, also showing syntopic LBC). Fifteen (75%) of these 20 PTCLs with B-lineage proliferation yielded monoclonal TR gene rearrangements, and only two (10%) showed IGH monoclonality, which was transient in one case. Three (18%) of the PTCLs with LBC had originally been misinterpreted as some form of HL. Conversely, of the remaining cases, three of four (75%) that had been diagnosed initially as some form of large cell non-HL (NHL), including two of three that were called 'anaplastic', had to be revised to grade II/syncytial nodular sclerosing (NS) HL, yielding polyclonal TcRgamma gene (TRG) rearrangements, with one case, in addition, disclosing a biallelic clonal IGH gene rearrangement that excluded anaplastic large cell lymphoma.

DISCUSSION/CONCLUSION

Paradoxically, monoclonality of TR rather than IGH gene rearrangement may more often be detectable in a predominantly dispersed ('hodgkinoid'), large B-lineage cell proliferation, consistent with release from immune regulation in the milieu of impaired immunosurveillance within a PTCL. This is compounded by the difficulty in ascertaining clonal IGH gene rearrangements resulting from (1) poor consensus primer hybridization due to somatic hypermutations, and (2) 'dilution' in a T-cell-rich milieu. These same difficulties also account for the long-elusive identification of the RS cell lineage. Conversely, anaplastic lymphoma, which is of non-B lineage, may be mimicked by NSHL, which is of B lineage.

Pediatric anaplastic lymphoma kinase-positive large B-cell lymphoma: a case report and review of the literature

We present a case of pediatric anaplastic lymphoma kinase-positive large B-cell lymphoma (ALK-positive LBCL) with a cervical, mesentery, and pelvis cavity mass. Histologic examination of the cervical mass revealed that the lesion was composed of diffuse large immunoblastic-like or plasmablastic-like tumor cells with a sinusoidal growth pattern. The tumor cells were strongly immunoreactive for ALK; revealed a granular cytoplasmic distribution; and were diffusely positive for CD45, CD4, CD138, epithelial membrane antigen, and multiple myeloma oncogene-1 but negative for CD20 and CD79a. The patient underwent 5 courses of cyclophosphamide, doxorubicin, vincristine, prednisone, and etoposid and obtained a remarkable clinical response with regression of mesentery and pelvis cavity mass. We suggest that this distinct subtype of large B-cell lymphoma should belong to the spectrum of pediatric lymphomas and that radiologic examination should be performed to inspect the progression of disease even if the patients experienced complete remission at initial chemotherapy.

Promising personalized therapeutic options for diffuse large B-cell Lymphoma Subtypes with oncogene addictions

Currently, two major classification systems segregate diffuse large B-cell lymphoma (DLBCL) into subtypes based on gene expression profiles and provide great insights about the oncogenic mechanisms that may be crucial for lymphomagenesis as well as prognostic information regarding response to current therapies. However, these current classification systems primarily look at expression and not dependency and are thus limited to inductive or probabilistic reasoning when evaluating alternative therapeutic options. The development of a deductive classification system that identifies subtypes in which all patients with a given phenotype require the same oncogenic drivers, and would therefore have a similar response to a rational therapy targeting the essential drivers, would significantly advance the treatment of DLBCL. This review highlights the putative drivers identified as well as the work done to identify potentially dependent populations. These studies integrated genomic analysis and functional screens to provide a rationale for targeted therapies within defined populations. Personalizing treatments by identifying patients with oncogenic dependencies via genotyping and specifically targeting the responsible drivers may constitute a novel approach for the treatment of DLBCL.

Inhibitors of the anaplastic lymphoma kinase

INTRODUCTION

Anaplastic lymphoma kinase (ALK) is a receptor tyrosine kinase normally expressed in the developing nervous tissue. Genetic alterations of ALK are associated with a number of cancers, including anaplastic large cell lymphoma (ALCL) and a subset of non-small cell lung cancer (NSCLC). Standard therapies for these diseases include surgery plus unspecific cytotoxic agents, with a low therapeutic window and significant treatment-associated systemic toxicity. A few small-molecule inhibitors of ALK kinase activity have been described in the recent years, some of which are currently undergoing clinical evaluation.

AREAS COVERED

Literature was searched for all ALK inhibitors that have entered clinical investigation, including published research articles and meeting abstracts. Data on pharmacokinetics, safety and efficacy of crizotinib, as well as preliminary clinical data for second-generation compounds, are reviewed. The issue of drug resistance is discussed.

EXPERT OPINION

Understanding the specific genetic aberration that causes cancer development and progression allows major advances in cancer therapy. Along the same way shown by imatinib in chronic myeloid leukemia, compounds that selectively target ALK are bringing a revolution in the treatment of ALK-positive tumors. Crizotinib has just been approved, and new more potent ALK inhibitors will shortly follow. These molecules represent another excellent proof-of-principle for targeted therapy.

Case report: A unique pediatric case of a primary CD8 expressing ALK-1 positive anaplastic large cell lymphoma of skeletal muscle

Primary involvement of skeletal muscle is a very rare event in ALK-1 positive anaplastic large cell lymphoma (ALCL). We describe a case of a 10-year old boy presenting with a three week history of pain and a palpable firm swelling at the dorsal aspect of the left thigh. Histological examination of the lesion revealed a tumoral and diffuse polymorphic infiltration of the muscle by large lymphoid cells. Tumor cells displayed eccentric, lobulated "horse shoe" or "kidney-shape" nuclei. The cells showed immunohistochemical positivity for CD30, ALK-1, CD2, CD3, CD7, CD8, and Perforin. Fluorescence in situ hybridization analysis revealed a characteristic rearrangement of the ALK-1 gene in 2p23 leading to the diagnosis of ALK-1 positive ALCL. Chemotherapy according to the ALCL-99-NHL-BFM protocol was initiated and resulted in a complete remission after two cycles. This case illustrates the unusual presentation of a pediatric ALCL in soft tissue with a good response to chemotherapy.

Anaplastic lymphoma kinase-positive large B-cell lymphoma: an underrecognized aggressive lymphoma

Anaplastic lymphoma kinase-(ALK-) positive large B-cell lymphoma (ALK+ LBCL) is a rare, aggressive tumor characterized by an immunoblastic or plasmablastic morphologic appearance, expression of ALK, CD138, CD45, EMA, and often IgA by immunohistochemistry, and characteristic chromosomal translocations or rearrangements involving the ALK locus. The morphologic and immunophenotypic overlap of this tumor with other hematologic and nonhematologic malignancies may result in misdiagnosis. The tumor has been identified in both pediatric and adult populations and demonstrates a male predominance. Presentation is most often nodal, particularly cervical. No association with immunocompromise or geographic location has been recognized. The most common gene rearrangement is between clathrin and ALK (t(2;17)(p23;q23)), resulting in the CLTC-ALK chimeric protein, although other fusions have been described. Response to conventional chemotherapy is poor. The recent introduction of the small molecule ALK inhibitor, crizotinib, may provide a potential new therapeutic option for patients with this disease.

KLC1-ALK: a novel fusion in lung cancer identified using a formalin-fixed paraffin-embedded tissue only

The promising results of anaplastic lymphoma kinase (ALK) inhibitors have changed the significance of ALK fusions in several types of cancer. These fusions are no longer mere research targets or diagnostic markers, but they are now directly linked to the therapeutic benefit of patients. However, most available tumor tissues in clinical settings are formalin-fixed and paraffin-embedded (FFPE), and this significantly limits detailed genetic studies in many clinical cases. Although recent technical improvements have allowed the analysis of some known mutations in FFPE tissues, identifying unknown fusion genes by using only FFPE tissues remains difficult. We developed a 5′-rapid amplification of cDNA ends-based system optimized for FFPE tissues and evaluated this system on a lung cancer tissue with ALK rearrangement and without the 2 known ALK fusions EML4-ALK and KIF5B-ALK. With this system, we successfully identified a novel ALK fusion, KLC1-ALK. The result was confirmed by reverse transcription-polymerase chain reaction and fluorescence in situ hybridization. Then, we synthesized the putative full-length cDNA of KLC1-ALK and demonstrated the transforming potential of the fusion kinase with assays using mouse 3T3 cells. To the best of our knowledge, KLC1-ALK is the first novel oncogenic fusion identified using only FFPE tissues. This finding will broaden the potential value of archival FFPE tissues and provide further biological and clinical insights into ALK-positive lung cancer.

Identification of anaplastic lymphoma kinase fusions in renal cancer: large-scale immunohistochemical screening by the intercalated antibody-enhanced polymer method

BACKGROUND

Several promising molecular-targeted drugs are used for advanced renal cancers. However, complete remission is rarely achieved, because none of the drugs targets a key molecule that is specific to the cancer, or is associated with "oncogene addiction" (dependence on one or a few oncogenes for cell survival) of renal cancer. Recently, an anaplastic lymphoma kinase (ALK) fusion, vinculin-ALK, has been reported in pediatric renal cell carcinoma (RCC) cases who have a history of sickle cell trait. In this context, ALK inhibitor therapy would constitute a therapeutic advance, as has previously been demonstrated with lung cancer, inflammatory myofibroblastic tumors, and anaplastic large cell lymphomas.

METHODS

Anti-ALK immunohistochemistry was used to screen 355 tumor tissues, using the intercalated antibody-enhanced polymer (iAEP) method. The cohort consisted of 255 clear cell RCCs, 32 papillary RCCs, 34 chromophobe RCCs, 6 collecting duct carcinomas, 10 unclassified RCCs, 6 sarcomatoid RCCs, and 12 other tumors.

RESULTS

Two patients (36- and 53-year-old females) were positive for ALK as determined by iAEP immunohistochemistry. Using 5'- rapid amplification of complementary DNA ends, we detected TPM3-ALK and EML4-ALK in these tumors. The results of this study were confirmed by fluorescence in situ hybridization assays. The 2 ALK-positive RCCs were unclassified (mixed features of papillary, mucinous cribriform, and solid patterns with rhabdoid cells) and papillary subtype. They comprised 2.3% of non-clear cell RCCs (2 of 88) and 3.7% of non-clear cell and nonchromophobe RCCs (2 of 54).

CONCLUSIONS

The results of this study indicate that ALK fusions also exist in adult RCC cases without uncommon backgrounds. These findings confirm the potential of ALK inhibitor therapy for selected cases of RCC.

Anaplastic large-cell lymphoma

The concept of anaplastic large-cell lymphoma (ALCL) has changed over the years because of a stream of new information and novel understanding regarding the cell of origin, biology, genetics, and clinical features of these neoplasms. This new information has led to the current classification proposed by the expert reviewers of the World Health Organization. The objective of this review is to present the most updated information on the cytologic and histologic features of these entities, with a special reference to diagnostic algorithms. A detailed description of the genetic aberrations and the pathogenetic mechanisms leading to transformation is presented. The clinical features of ALCL and novel tailored strategies are briefly illustrated.

Large B-cell lymphomas with plasmablastic differentiation: a biological and therapeutic challenge

Plasmablastic differentiation can be found in a variety of large B-cell lymphomas, including plasmablastic lymphoma, ALK-positive large B-cell lymphoma, primary effusion lymphoma, large B-cell lymphoma arising in human herpesvirus-8 (HHV-8)-associated multicentric Castleman disease and diffuse large B-cell lymphoma (DLBCL) with partial plasmablastic phenotype. These tumors are characterized by acquisition of the transcriptional profile of plasma cells (with overexpression of PRDM1/Blimp1 and XBP1s, in concert with extinction of the B-cell differentiation program) by proliferating immunoblasts. This particular biological entity, i.e. large B-cell lymphoma with plasmablastic differentiation, is almost always associated with an aggressive clinical behavior. This review summarizes the current knowledge of the biological basis of plasmablastic differentiation in large B-cell lymphomas, the diagnostic borders with DLBCL and multiple myeloma, the associated adverse molecular events (with concomitant MYC, p53 and ALK alterations) and the potential therapeutic targets so far identified (including the unfolded protein response pathway). The highly aggressive nature of these lymphomas and the relative paucity of molecular data available highlight the need for deeper insights into the molecular pathogenesis of large B-cell lymphomas with plasmablastic differentiation in order to identify new and effective alternative treatments.

ALK-positive extramedullary plasmacytoma with expression of the CLTC-ALK fusion transcript

Anaplastic lymphoma kinase (ALK)-positive non-Hodgkin lymphoma (NHL) was long thought to be a disease occurring uniquely in T or null-cell lymphomas. More recently, however, a small number of B-lineage lymphomas have been reported to express ALK fusion genes. These tumors often exhibit a plasmablastic morphology, a finding which prompted our interest in looking for ALK fusions in plasma cell neoplasms. We studied 46 cases of extramedullary plasmacytoma by immunostaining with anti-ALK antibody and fluorescence in situ hybridization (FISH) analysis using an ALK break-apart probe and found one case to be ALK protein-positive and demonstrated the disruption of the ALK gene in this case. Immunohistochemistry showed that the tumor cells were strongly positive for CD138, VS38c, and epithelial membrane antigen, but lacked expression of CD20, CD79a, CD45, and CD30. Both RT-PCR and genomic DNA-PCR confirmed the CLTC-ALK fusion. This finding expands the lists of the ALK-positive tumors, and ALK-positive extramedullary plasmacytoma may benefit from the treatment of ALK inhibitor in the future.

Anaplastic lymphoma kinase in human cancer

The receptor tyrosine kinases (RTKs) play a critical role, controlling cell proliferation, survival, and differentiation of normal cells. Their pivotal function has been firmly established in the pathogenesis of many cancers as well. The anaplastic lymphoma kinase (ALK), a transmembrane RTK, originally identified in the nucleophosmin (NPM)-ALK chimera of anaplastic large cell lymphoma, has emerged as a novel tumorigenic player in several human cancers. In this review, we describe the expression of the ALK-RTK, its related fusion proteins, and their molecular mechanisms of activation. Novel tailored strategies are briefly illustrated for the treatment of ALK-positive neoplasms.

Hypoxia-microRNA-16 downregulation induces VEGF expression in anaplastic lymphoma kinase (ALK)-positive anaplastic large-cell lymphomas

The anaplastic lymphoma kinase (ALK), tyrosine kinase oncogene is implicated in a wide variety of cancers. In this study we used conditional onco-ALK (NPM-ALK and TPM3-ALK) mouse MEF cell lines (ALK+ fibroblasts) and transgenic models (ALK+ B-lymphoma) to investigate the involvement and regulation of angiogenesis in ALK tumor development. First, we observed that ALK expression leads to downregulation of miR-16 and increased Vascular Endothelial Growth Factor (VEGF) levels. Second, we found that modification of miR-16 levels in TPM3-ALK MEF cells greatly affected VEGF levels. Third, we demonstrated that miR-16 directly interacts with VEGF mRNA at the 3'-untranslated region and that the regulation of VEGF by miR-16 occurs at the translational level. Fourth, we showed that expression of both the ALK oncogene and hypoxia-induced factor 1α (HIF1α) is a prerequisite for miR-16 downregulation. Fifth, in vivo, miR-16 gain resulted in reduced angiogenesis and tumor growth. Finally, we highlighted an inverse correlation between the levels of miR-16 and VEGF in human NPM-ALK+ Anaplastic Large Cell Lymphomas (ALCL). Altogether, our results demonstrate, for the first time, the involvement of angiogenesis in ALK+ ALCL and strongly suggest an important role for hypoxia-miR-16 in regulating VEGF translation.

Inhibition of Rac controls NPM-ALK-dependent lymphoma development and dissemination

Nucleophosmin-anaplastic lymphoma kinase (NPM–ALK) is a tyrosine kinase oncogene responsible for the pathogenesis of the majority of human ALK-positive lymphomas. We recently reported that it activated the Rac1 GTPase in anaplastic large-cell lymphoma (ALCL), leading to Rac-dependent formation of active invadopodia required for invasiveness. Herein, we went further into the study of this pathway and used the inhibitor of Rac, NSC23766, to validate its potential as a molecular target in ALCL in vitro and in vivo in a xenograft model and in a conditional model of NPM–ALK transgenic mice. Our data demonstrate that Rac regulates important effectors of NPM–ALK-induced transformation such as Erk1/2, p38 and Akt. Moreover, inhibition of Rac signaling abrogates NPM–ALK-elicited disease progression and metastasis in mice, highlighting the potential of small GTPases and their regulators as additional therapic targets in lymphomas.

Cutaneous anaplastic large-cell lymphoma should be evaluated for systemic involvement regardless of ALK-1 status: case reports and review of literature

Anaplastic large-cell lymphoma (ALCL) is a lymphoma that expresses CD30. Cutaneous ALCL presents either as primary cutaneous disease or as secondary skin involvement due to the systemic disease. Herein, we describe two patients who presented to dermatology for evaluation of skin lesions diagnosed by non-dermatologists as a cutaneous abscess and lupus erythematosus, respectively. Upon investigation by a team of medical dermatologists and dermatopathologists, systemic ALCL with secondary skin involvement was discovered in both patients. The majority of cases of systemic ALCL with cutaneous involvement express anaplastic lymphoma kinase-1 (ALK-1), and are associated with a more favorable prognosis than ALK-1-negative cases. However, cutaneous ALCL regardless of ALK-1 status may be secondary to systemic lymphoma. This article stresses the importance of dermatologists being aware of the diagnosis of systemic lymphoma based on cutaneous findings, and being aggressive in initiating appropriate diagnostic testing. Primary cutaneous ALCL and systemic ALCL are reviewed.

Inhibition of anaplastic lymphoma kinase (ALK) activity provides a therapeutic approach for CLTC-ALK-positive human diffuse large B cell lymphomas

ALK positive diffuse large B-cell lymphomas (DLBCL) are a distinct lymphoma subtype associated with a poor outcome. Most of them feature a t(2;17) encoding a clathrin (CLTC)-ALK fusion protein. The contribution of deregulated ALK-activity in the pathogenesis and maintenance of these DLBCLs is not yet known. We established and characterized the first CLTC-ALK positive DLBCL cell line (LM1). LM1 formed tumors in NOD-SCID mice. The selective ALK inhibitor NVP-TAE684 inhibited growth of LM1 cells in vitro at nanomolar concentrations. NVP-TAE684 repressed ALK-activated signalling pathways and induced apoptosis of LM1 DLBCL cells. Inhibition of ALK-activity resulted in sustained tumor regression in the xenotransplant tumor model. These data indicate a role of CLTC-ALK in the maintenance of the malignant phenotype thereby providing a rationale therapeutic target for these otherwise refractory tumors.

Pulmonary inflammatory myofibroblastic tumor expressing a novel fusion, PPFIBP1-ALK: reappraisal of anti-ALK immunohistochemistry as a tool for novel ALK fusion identification

PURPOSE

The anaplastic lymphoma kinase (ALK) inhibitor crizotinib has been used in patients with lung cancer or inflammatory myofibroblastic tumor (IMT), both types harboring ALK fusions. However, detection of some ALK fusions is problematic with conventional anti-ALK immunohistochemistry because of their low expression. By using sensitive immunohistochemistry, therefore, we reassessed "ALK-negative" IMT cases defined with conventional immunohistochemistry (approximately 50% of all examined cases).

EXPERIMENTAL DESIGN

Two cases of ALK-negative IMT defined with conventional anti-ALK immunohistochemistry were further analyzed with sensitive immunohistochemistry [the intercalated antibody-enhanced polymer (iAEP) method].

RESULTS

The two "ALK-negative" IMTs were found positive for anti-ALK immunohistochemistry with the iAEP method. 5'-rapid amplification of cDNA ends identified a novel partner of ALK fusion, protein-tyrosine phosphatase, receptor-type, F polypeptide-interacting protein-binding protein 1 (PPFIBP1) in one case. The presence of PPFIBP1-ALK fusion was confirmed with reverse transcriptase PCR, genomic PCR, and FISH. We confirmed the transforming activities of PPFIBP1-ALK with a focus formation assay and an in vivo tumorigenicity assay by using 3T3 fibroblasts infected with a recombinant retrovirus encoding PPFIBP1-ALK. Surprisingly, the fusion was also detected by FISH in the other case.

CONCLUSIONS

Sensitive immunohistochemical methods such as iAEP will broaden the potential value of immunohistochemistry. The current ALK positivity rate in IMT should be reassessed with a more highly sensitive method such as iAEP to accurately identify those patients who might benefit from ALK-inhibitor therapies. Novel ALK fusions are being identified in various tumors in addition to IMT, and thus a reassessment of other "ALK-negative" cancers may be required in the forthcoming era of ALK-inhibitor therapy.

Renal cell carcinoma with novel VCL-ALK fusion: new representative of ALK-associated tumor spectrum

Renal cell carcinoma represents a model for contemporary classification of solid tumors; however, unusual and unclassifiable cases exist and are not rare in children and young adults. The anaplastic lymphoma kinase (ALK) gene has recently been implicated in subsets of pulmonary, esophageal, breast, and colon cancers. These findings strengthen the importance of molecular classification of carcinomas across different organ sites, especially considering the evolving targeted anticancer therapies with ALK inhibitors. In the current study of six pediatric renal cell carcinomas, two cases exhibited structural karyotypic abnormalities involving the ALK locus on chromosomal band 2p23. Fluorescence in situ hybridization (FISH) studies were positive for an ALK rearrangement in one case, and subsequent 5' rapid amplification of cDNA ends analysis of this tumor revealed that the 3' portion of the ALK transcript encoding for the kinase domain was fused in frame to the 5' portion of vinculin (VCL, NM_003373). The new fusion gene is predicted to have an open reading frame of 4122 bp encoding for a 1374-aa oncoprotein; its expression was shown by immunoblotting with anti-VCL and anti-ALK antibodies in tumor tissue lysates. Immunohistochemistry with the same antibodies demonstrated cytoplasmic and subplasmalemmal localization of the oncoprotein determined by its N-terminal VCL portion. FISH with a custom-designed VCL-ALK dual-fusion probe set confirmed the presence of the fusion in neoplastic cells and demonstrated the potential clinical utility of this approach for detecting VCL-ALK in routinely processed tissue. The five remaining pediatric renal cell carcinomas did not show ALK rearrangement by FISH or ALK expression by immunohistochemistry. The data identify the kidney as a new organ site for ALK-associated carcinomas and VCL as a novel ALK fusion partner. The results should prompt further studies to advance the molecular classification of renal cell carcinoma and help to select patients who would benefit from appropriate targeted therapies.

Aggressive B-cell lymphomas: a review of new and old entities in the WHO classification

Aggressive B-cell lymphomas are clinically and pathologically diverse and reflect multiple pathways of transformation. The 2008 World Health Organization (WHO) classification reflects this complexity with the addition of several new entities and variants. Whereas MYC translocations have long been associated with Burkitt lymphoma (BL), deregulation of MYC has been shown to occur in other aggressive B-cell lymphomas, most often as a secondary event. Lymphomas with translocations of both MYC and BCL2 are highly aggressive tumors, with a high failure rate with most treatment protocols. These "double-hit" lymphomas are now separately delineated in the WHO classification as B-cell lymphoma, unclassifiable, with features intermediate between diffuse large B-cell lymphoma (DLBCL) and BL. A MYC translocation is also found uncommonly in DLBCL, but the clinical consequences of this in the absence of a double hit are not yet fully delineated. Most recently, MYC translocations have been identified as a common secondary event in plasma cell neoplasms, seen in approximately 50% of plasmablastic lymphoma. Another area that has received recent attention is the spectrum of EBV-driven B-cell proliferations in patients without iatrogenic or congenital immunosuppression; most of these occur in patients of advanced age and include the EBV-positive large B-cell lymphomas of the elderly.

ALK rearrangement in sickle cell trait-associated renal medullary carcinoma

Renal Medullary Carcinoma (RMC) is an aggressive malignancy that affects young black individuals with sickle cell trait. No effective treatment is available, resulting in an ominous clinical course, with overall survival averaging less than four months. We report rearrangement of the ALK receptor tyrosine kinase in a pediatric case of RMC harboring a t(2;10)(p23;q22) translocation. Mass spectrometry-based proteomic evaluation identified a novel ALK oncoprotein in which the cytoskeletal protein vinculin (VCL) was fused to the ALK kinase domain. The resulting VCL-ALK fusion does not contain known self-association domains, but includes the talin binding domains of vinculin. We demonstrate coprecipitation of strongly tyrosine phosphorylated talins with the VCL-ALK oncoprotein, suggesting that ALK oncogenic crossphosphorylation is mediated by interactions between neighboring VCL-ALK proteins on a talin scaffold. This report widens the spectrum of ALK-related tumors and ALK fusion partners, and provides a rationale for treating RMC with targeted ALK inhibitors.

Diagnosis of Nodal Peripheral T-Cell Lymphomas

Lymph node-based peripheral T-cell lymphomas are rare and exhibit a morphologic spectrum that overlaps with reactive lymphoid hyperplasia, B-cell lymphomas, and Hodgkin lymphoma, presenting a diagnostic challenge. This review focuses on the major categories of lymph node-based peripheral T-cell lymphomas recognized by the 2008 World Health Organization Classification of Tumours of Haematopoietic and Lymphoid Tissues. Diagnostic strategies for approaching T-cell neoplasms using a combined clinical, morphologic, immunophenotypic, and genetic approach are presented. Practical information to aid in distinguishing peripheral T-cell lymphomas from other hematologic malignancies and benign conditions is provided.

Herpesvirus-Associated B-cell Proliferations

This article reviews the spectrum of Epstein-Barr virus and Kaposi sarcoma herpesvirus (KSHV/HHV-8)-associated B-cell lymphoid proliferations, their pathologic features and clinical presentation, diagnostic criteria, and pathogenetic aspects. Emphasis is on the differential diagnosis issues and difficulties that the pathologist may face for the correct identification and interpretation of these lesions.

CD4-positive diffuse large B cell lymphoma identified by flow cytometry: two case reports

We report two cases of diffuse large B cell lymphoma (DLBCL), both occurring in the small bowel, which coexpress PAX5, weak or no CD20 and the CD4 antigen. The CD4 was initially identified by flow cytometry and then confirmed by immunohistochemistry. CD4 is a representative marker for helper T-lymphocytes and is present on a subset of thymocytes, peripheral T cells and monocytes or macrophages. Unlike CD2 and CD5, no B cell fractions are known to express CD4. It might be hypothesized that the deregulated control of gene expression in malignant B cells, in particular PAX5, leads to the activation of some silent or repressed genes of T cell differentiation. Although lineage infidelity is described in some B lymphomas, it remains as an uncommon phenomenon; to our knowledge, cases reported here are the first two cases of DLBCL of the gastrointestinal tract coexpressing the CD4 antigen to be described to date.

Conditional TPM3-ALK and NPM-ALK transgenic mice develop reversible ALK-positive early B-cell lymphoma/leukemia

NPM-ALK (nucleophosmin-anaplastic lymphoma kinase) and TPM3-ALK (nonmuscular tropomyosin 3-anaplastic lymphoma kinase) are oncogenic tyrosine kinases implicated in the pathogenesis of human ALK-positive lymphoma. We report here the development of novel conditional mouse models for ALK-induced lymphomagenesis, with the use of the tetracycline regulatory system under the control of the EμSRα enhancer/promoter. The expression of either oncogene resulted in the arrest of the differentiation of early B cells and lymphomagenesis. We also observed the development of skin keratoacanthoma lesions, probably because of aberrant ALK expression in keratinocytes. The inactivation of the ALK oncogene on doxycycline treatment was sufficient to induce sustained regression of both hematopoietic tumors and skin disease. Importantly, treatment with the specific ALK inhibitor (PF-2341066) also reversed the pathologic states, showing the value of these mouse models for the validation of ALK tyrosine kinase inhibitors. Thus, our results show (1) that NPM-ALK and TPM3-ALK oncogenes are sufficient for lymphoma/leukemia development and required for tumor maintenance, hence validating ALK as potentially effective therapeutic target; and (2) for the first time, in vivo, the equal tumorigenic potential of the NPM-ALK and TPM3-ALK oncogenic tyrosine kinases. Our models offer a new tool to investigate in vivo the molecular mechanisms associated with ALK-induced lymphoproliferative disorders.