Early lymphoid lesions: conceptual, diagnostic and clinical challenges

AID in non-Hodgkin B-cell lymphomas: The consequences of on- and off-target activity

Activation induced cytidine deaminase (AID) is a key element of the adaptive immune system, required for immunoglobulin isotype switching and affinity maturation of B-cells as they undergo the germinal center (GC) reaction in peripheral lymphoid tissue. The inherent DNA damaging activity of this enzyme can also have off-target effects in B-cells, producing lymphomagenic chromosomal translocations that are characteristic features of various classes of non-Hodgkin B-cell lymphoma (B-NHL), and generating oncogenic mutations, so-called aberrant somatic hypermutation (aSHM). Additionally, AID has been found to affect gene expression through demethylation as well as altered interactions between gene regulatory elements. These changes have been most thoroughly studied in B-NHL arising from GC B-cells. Here, we describe the most common classes of GC-derived B-NHL and explore the consequences of on- and off-target AID activity in B and plasma cell neoplasms. The relationships between AID expression, including effects of infection and other exposures/agents, mutagenic activity and lymphoma biology are also discussed.

Precursory or early lesions of follicular lymphoma: clinical features, pathology, and genetics

Follicular lymphoma (FL) is an indolent B-cell lymphoma with a germinal center (GC) B cell phenotype that typically harbors t(14;18)(q32;q21). t(14;18) juxtaposes IGH on 14q32 and BCL2 on 18q21, resulting in overexpression of the anti-apoptotic BCL2 protein. However, t(14;18) is also found in the peripheral blood or lymphoid nodes (LNs) of otherwise healthy individuals. Moreover, overt FL has several additional gene alterations involved in epigenetic modification, JAK/STAT signaling, immune modulation, and NF-κB signaling, indicating multi-step lymphomagenesis in FL. There are two early or precursory lesions of FL: t(14;18)-positive cells in the peripheral blood of otherwise healthy individuals and in situ follicular B-cell neoplasm (ISFN). t(14;18)-positive cells are found in 10%-50% of healthy populations, and their incidence and frequency increase with age. The detection of t(14;18) in peripheral blood is a predictive factor for an increased risk of overt FL development. In contrast, ISFN is a histopathologically recognizable precursory lesion, in which t(14;18)-positive cells are confined to the GC of otherwise reactive LNs. ISFN is usually detected incidentally, with an incidence ranging from 2.0% to 3.2%. Occasional ISFN cases have concurrent or metachronous clonally related overt FL or aggressive B-cell lymphoma of a GC phenotype. t(14;18)-positive cells in peripheral blood and isolated ISFN, by themselves, are asymptomatic with limited clinical significance; however, investigations of t(14;18)-positive precursory or early lesions offer meaningful insights into the pathogenesis of FL. This review summarizes the epidemiology, clinical features, pathology, and genetics of precursory or early lesions of FL.

PNMZL and PTFL: morphological variants with a common molecular profile - a unifying hypothesis

PNMZL has a molecular landscape characterized by low genomic complexity and frequent MAP2K1, TNFRSF14, and IRF8 alterations.

The histologic and molecular features of PNMZL and PTFL suggest that they represent a morphologic spectrum of the same biologic entity.

Pediatric nodal marginal zone lymphoma (PNMZL) is an uncommon B-cell neoplasm affecting mainly male children and young adults. This indolent lymphoma has distinct characteristics that differ from those of conventional nodal marginal zone lymphoma (NMZL). Clinically, it exhibits overlapping features with pediatric-type follicular lymphoma (PTFL). To explore the differences between PNMZL and adult NMZL and its relationship to PTFL, a series of 45 PNMZL cases were characterized morphologically and genetically by using an integrated approach; this approach included whole-exome sequencing in a subset of cases, targeted next-generation sequencing, and copy number and DNA methylation arrays. Fourteen cases (31%) were diagnosed as PNMZL, and 31 cases (69%) showed overlapping histologic features between PNMZL and PTFL, including a minor component of residual serpiginous germinal centers reminiscent of PTFL and a dominant interfollicular B-cell component characteristic of PNMZL. All cases displayed low genomic complexity (1.2 alterations per case) with recurrent 1p36/TNFRSF14 copy number–neutral loss of heterozygosity alterations and copy number loss (11%). Similar to PTFL, the most frequently mutated genes in PNMZL were MAP2K1 (42%), TNFRSF14 (36%), and IRF8 (34%). DNA methylation analysis revealed no major differences between PTFL and PNMZL. Genetic alterations typically seen in conventional NMZL were absent in PNMZL. In summary, overlapping clinical, morphologic, and molecular findings (including low genetic complexity; recurrent alterations in MAP2K1, TNFRSF14, and IRF8; and similar methylation profiles) indicate that PNMZL and PTFL are likely part of a single disease with variation in the histologic spectrum. The term “pediatric-type follicular lymphoma with and without marginal zone differentiation” is suggested.

SIRT1-SIRT7 Expression in Patients with Lymphoproliferative Disorders Undergoing Hematopoietic Stem Cell Mobilization

Sirtuins are involved in the fate of hematopoietic stem cells (HSCs), including their metabolism, stress response, differentiation, migration, and apoptosis. The aim of this study was to explore SIRT1-7 expression during HSC mobilization. The study included 50 patients with lymphoproliferative disorders (39 multiple myeloma, 11 lymphoma). Samples were taken before mobilization (day 0) and on the day of first apheresis (day A). The sirtuin expression was evaluated by the Droplet Digital PCR (ddPCR) method. A significant increase of the SIRT1, SIRT2, SIRT3, SIRT5, SIRT6, and SIRT7 levels measured at day A as compared to baseline was observed. The study revealed a positive correlation between SIRT5, SIRT6, and SIRT7 expression and the CD34+ peak value in peripheral blood and the number of CD34+ cells collected on day A. Patients from the SIRT7 “high expressors” group collected more CD34+ cells on day A than “low expressors”. Upregulated expressions of SIRT3 and SIRT7 on the day of first apheresis were observed in patients in complete remission status (CR) as compared to the non-CR group. Our results suggest that the investigated sirtuins may influence the HSC migration and hematopoietic landscape during mobilization. SIRT5, SIRT6, and SIRT7 may be associated with the efficacy of HSC mobilization.

Natural Killer Cell Enteropathy With Extraintestinal Involvement: Presenting as Symptomatic Anemia

Natural killer (NK) cell enteropathy is a newly described disease entity with benign behavior and an indolent clinical course, characterized by the atypical proliferation of NK cells throughout the gastrointestinal tract. The exact etiology is unknown. It closely mimics NK/T-cell lymphoma. We describe this atypical entity in a young adult man presenting with vague upper gastrointestinal symptoms and anemia requiring blood transfusion. The response to budesonide therapy points toward a possible low-grade autoimmune process. Considering the benign behavior and self-limiting course, recognizing this entity is essential to avoid over the investigation and aggressive, inappropriate therapy.

Multifocal in situ mantle cell neoplasia of the ileocecal region: a case report with simultaneous nodal and extranodal involvement

In situ mantle cell neoplasia (ISMCN) is a rare entity of disputed clinical significance. We report an additional case, unusual by its presentation in the large intestine and its multifocal involvement of several nodal and extranodal sites. The diagnosis was made in a 46-year-old male patient from a surgical specimen resected for cecal adenocarcinoma. Gross examination showed multiple small polypoid lesions surrounding the ileocecal valve, corresponding to lymphoid aggregates with hyperplastic follicles. Numerous cyclin D1/SOX11+ lymphoid cells, harboring the t(11;14)(q13;q32) translocation, were present in the inner layers of mantle zones. The same lesions were found in the ileum, the appendix, and the regional lymph nodes. The final diagnosis was multifocal ISMCN of the ileocecal region, with both nodal and extra-nodal involvement. A simple surveillance was decided. Our observation expands the clinical spectrum of the disease and underlines the necessity to closely examine even normal-appearing reactive lymphoid tissues.

An Enteropathy-like Indolent NK-Cell Proliferation Presenting in the Female Genital Tract

Natural killer (NK) cell enteropathy is a lymphoproliferative disorder, initially described by Mansoor and colleagues, that presents in the gastrointestinal tract, and is often mistaken for extranodal NK/T-cell lymphoma on first assessment. This population of cells in this process have an NK-cell phenotype (CD3, CD56, CD2, CD7), lacks evidence of Epstein-Barr virus infection, has germline rearrangement of the T-cell receptor, and a very indolent clinical course. Indeed, many of such patients had been originally diagnosed as having an NK/T-cell lymphoma, and subsequently received chemotherapy. We report a unique case where an indolent lymphoproliferative disorder with features that resemble NK-cell enteropathy is encountered for the first time outside the gastrointestinal tract, specifically in the female genitourinary tract. We provide morphologic, immunophenotypic, and molecular documentation of such, in association with a completely indolent clinical behavior of this type of process.

Composite monoclonal B-cell lymphocytosis and MYD88 L265P-positive lymphoplasmacytic lymphoma in a patient with IgM light chain amyloidosis: Case report

Monoclonal B-cell lymphocytosis (MBL) is an early or precursor asymptomatic proliferation of chronic lymphocytic lymphoma (CLL)-like B-cells. Lymphoplasmacytic lymphoma (LPL), often clinically associated with Waldenström macroglobulinemia, is a B-cell neoplasm characterized by frequent MYD88 L265P mutation. Here, we report a rare composite MBL and LPL in a patient with IgM light chain (AL) amyloidosis. A 74-year-old male with a known IgM monoclonal protein developed proteinuria. No lymphocytosis was detected. Renal biopsy showed deposition of AL λ amyloid in the glomeruli and vessels. Subsequent bone marrow biopsy revealed nodular atypical CLL-like small B-cell proliferation and scattered peripheral LPL. Immunohistochemistry and/or flow cytometry revealed that the atypical CLL-like population expressed CD19, CD20, CD5, weak CD23, LEF-1 and diminished surface Igκ. The LPL was positive for CD19, CD20 and surface Igλ. Using laser-capture microdissection and allele-specific polymerase chain reaction, we confirmed that MYD88 L265P was detectable in the LPL but not in the atypical CLL-like population. Thus, we demonstrated that these two populations were clonally independent, and made the diagnosis of composite MBL and LPL. An integrated clinical, pathological, immunophenotypic and genetic assessment is essential in such complicated cases, and especially 'clone-specific' MYD88 genotyping may facilitate the differential diagnoses of low-grade B-cell lymphomas.

What do we know about duodenal-type follicular lymphoma? From pathological definition to treatment options

Duodenal-type follicular lymphoma (DFL) is a newly recognised variant of follicular lymphoma (FL), although little is known about its biology and clinical evolution. In general, patients tend to have mild symptoms and do not require therapy, comparable with other forms of low-tumour burden asymptomatic FL. Specific pathological features, such as a dendritic cell meshwork, low expression of CD10 and upregulation of activation-induced cytidine deaminase can help the diagnosis. The molecular landscape of DFL is similar to the classical nodal presentation of FL, although studies using gene expression profiling demonstrate a close relation with MALT lymphomas. Markers associated with inflammation have suggested that the microenvironment plays a likely role in the pathogenesis of DFL and its low progression rate. Clinical series published vary between 20-63 patients with an estimated overall survival between 92-100% and a median follow-up ranging between 20 and 107 months. Treatment options include a watch and wait strategy, rituximab monotherapy and radiotherapy. In this review, we summarise current pathological data and treatment studies in DFL.

Update on Gastrointestinal Lymphomas

Herein we review the following selection of gastrointestinal lymphomas: monomorphic epitheliotropic intestinal T-cell lymphoma; indolent T-cell lymphoproliferative disorder of the gastrointestinal tract; intestinal T-cell lymphoma, not otherwise specified; duodenal-type follicular lymphoma; and Epstein-Barr virus-positive mucocutaneous ulcer. Definitions reflect the 2016 revision of the World Health Organization classification of lymphoid neoplasms. Clinical, morphologic, and immunophenotypic characteristics of each entity are emphasized.

Anaplastic Large Cell Lymphoma: Contemporary Concepts and Optimal Management

Anaplastic Large Cell Lymphomas (ALCL) are clinically aggressive and pathologically distinct lymphoid neoplasms that originate from a mature post-thymic T-cell. The contemporary World Health Organization (WHO) Classification of Haematologic Malignancies recognizes two distinct subtypes of systemic ALCL: Anaplastic Lymphoma Kinase (ALK)-negative, and ALK-positive. An additional unique subtype of ALCL is known to arise after prolonged exposure to breast implants, known as Breast Implant Associated ALCL (BIALCL). While histologic features of ALCL subtypes have significant overlap, genomic studies suggest the unique pathophysiology and molecular events of tumorigenesis. As a group, ALCLs are rare among non-Hodgkin lymphomas comprising 1-3% overall. There seems to be age and geographic predilection with ALK-positive ALCL affecting younger individuals and being diagnosed more frequently in North America than Europe. Both subtypes are quite uncommon in Hispanic and Asian populations. ALK-positive ALCL patients have a better overall prognosis than those with ALK-negative ALCL, and clinical features at presentation (i.e., International Prognostic Index, IPI) define the outcome in both subtypes. Molecular events affecting DUSP22 and TP63 have been reported to predict survival outcomes as well, with former being favorable, and the latter an unfavorable prognostic marker. Multiagent CHOP-like chemotherapy remains a standard of care for newly diagnosed ALCL patients treated with curative intent and provide a chance of cure for the majority of ALK-positive ALCL patients, and at least half of the ALK-negative ALCL patients. The role of consolidative high-dose therapy and autologous hematopoietic stem cell transplantation remains unclear. Novel targeted agents are actively being investigated for their role in initial therapy. New immunoconjugates, targeted kinase inhibitors, and transgenic autologous T-cells are being studied in patients with relapsed and refractory disease. This review will discuss contemporary concepts in pathogenesis and management of systemic ALCL. The biology and management of primary cutaneous ALCL will be discussed elsewhere.

Diagnosis and classification of lymphoma: Impact of technical advances

Our current understanding of the normal lymphoid system informs the modern classification of lymphomas. B-cell, T-cell, and natural killer-cell neoplasms often recapitulate normal stages of lymphoid cell differentiation and function. Moreover, the clinical manifestations of lymphomas often reflect the normal function of lymphoid cells in vivo. The multiparameter approach to classification adopted by the Revised European and American Lymphoma and subsequent WHO classifications facilitates the interpretation of clinical and translational studies, and provides a framework for the discovery of molecular alterations that drive these tumors. An accurate and precise classification of disease entities facilitates the discovery of the molecular basis of lymphoid neoplasms in the basic science laboratory, and leads to new diagnostic tools that play a role in clinical diagnosis.

Smoldering mantle cell lymphoma

Background

Mantle cell lymphoma (MCL) is an aggressive disease, with poor prognosis and a limited survival. However, some patients with indolent MCL can survive beyond 7~10 years. These patients remain largely asymptomatic and can be in observation for a long time without any treatment. The process of “wait and watch” leaves these patients with the potential risk of evolution to classic, aggressive MCL. On the other hand, early treatment for these patients may not impact overall survival but rather affects the quality of life. Therefore, it is essential to clearly identify this type of indolent MCL at the time of diagnosis.

Results

Reported findings of indolent presentation of MCL include: lack of B symptoms, normal serum lactic dehydrogenase (LDH) and β2-microglobulin levels (β2M), low MCL-International Prognostic Index (MIPI) score, maximum tumor diameter less than 3 cm, spleen size < 20 cm, positron emission tomography/computerized tomography with the Standard Uptake Value max <6, Ki-67 less than 30%, with some particular immunophenotype, such as CD5 and CD38 negative, markedly increased CD23 positive lymphocytes proportions, high expression of CD200, kappa light chain restriction, without C-myc, TP53 and NOTCH1/2 mutations, non-blastoid/pleomorphic histology, and no tumor growth on reevaluation every 2~3 months (followed for at least 6 months). Imaging evaluation may only be performed in the presence of disease-related symptoms or organ involvement. Meanwhile, if novel nodal or extranodal lesion is found, biopsy is mandatory to exclude lymphoma.

Common clinopathological forms of indolent presentations include monoclonal B lymphocytosis with t (11; 14); “indolent leukemic” presentation of MCL with involvement of peripheral blood, bone marrow involvement, splenomegaly, and minimal lymphadenopathies and in situ lymphoma (often found in lymph nodes removed for other reasons, and in gastrointestinal biopsies).

Conclusions

Considering these distinct indolent clinical presentations with particular features in cytology and gene mutational status, we propose to include these MCL clinical presentations under the umbrella of “Smoldering Mantle Cell Lymphoma”.

Understanding the New WHO Classification of Lymphoid Malignancies: Why It's Important and How It Will Affect Practice

Improved delineation of lymphoid malignancy biology has prompted refinement of the 2008 World Health Organization (WHO) classification of hematopoietic and lymphoid tumors with a new framework introduced in 2016. This knowledge has provided valuable insights regarding management. Early clonal proliferations have been set apart given their limited potential for malignant dissemination. Increasing knowledge of molecular drivers of aggressive lymphomas has allowed subclassification and opportunity for clinical investigations to personalize therapy. New insights into T-cell pathophysiology has allowed grouping based on shared molecular and cellular features. This article will summarize the key changes in terms of diagnosis and histopathologic definitions, the impact of these changes on clinical management, and the challenges of future research in this field.

Precancer Atlas to Drive Precision Prevention Trials

Cancer development is a complex process driven by inherited and acquired molecular and cellular alterations. Prevention is the holy grail of cancer elimination, but making this a reality will take a fundamental rethinking and deep understanding of premalignant biology. In this Perspective, we propose a national concerted effort to create a Precancer Atlas (PCA), integrating multi-omics and immunity - basic tenets of the neoplastic process. The biology of neoplasia caused by germline mutations has led to paradigm-changing precision prevention efforts, including: tumor testing for mismatch repair (MMR) deficiency in Lynch syndrome establishing a new paradigm, combinatorial chemoprevention efficacy in familial adenomatous polyposis (FAP), signal of benefit from imaging-based early detection research in high-germline risk for pancreatic neoplasia, elucidating early ontogeny in BRCA1-mutation carriers leading to an international breast cancer prevention trial, and insights into the intricate germline-somatic-immunity interaction landscape. Emerging genetic and pharmacologic (metformin) disruption of mitochondrial (mt) respiration increased autophagy to prevent cancer in a Li-Fraumeni mouse model (biology reproduced in clinical pilot) and revealed profound influences of subtle changes in mt DNA background variation on obesity, aging, and cancer risk. The elaborate communication between the immune system and neoplasia includes an increasingly complex cellular microenvironment and dynamic interactions between host genetics, environmental factors, and microbes in shaping the immune response. Cancer vaccines are in early murine and clinical precancer studies, building on the recent successes of immunotherapy and HPV vaccine immune prevention. Molecular monitoring in Barrett's esophagus to avoid overdiagnosis/treatment highlights an important PCA theme. Next generation sequencing (NGS) discovered age-related clonal hematopoiesis of indeterminate potential (CHIP). Ultra-deep NGS reports over the past year have redefined the premalignant landscape remarkably identifying tiny clones in the blood of up to 95% of women in their 50s, suggesting that potentially premalignant clones are ubiquitous. Similar data from eyelid skin and peritoneal and uterine lavage fluid provide unprecedented opportunities to dissect the earliest phases of stem/progenitor clonal (and microenvironment) evolution/diversity with new single-cell and liquid biopsy technologies. Cancer mutational signatures reflect exogenous or endogenous processes imprinted over time in precursors. Accelerating the prevention of cancer will require a large-scale, longitudinal effort, leveraging diverse disciplines (from genetics, biochemistry, and immunology to mathematics, computational biology, and engineering), initiatives, technologies, and models in developing an integrated multi-omics and immunity PCA - an immense national resource to interrogate, target, and intercept events that drive oncogenesis. Cancer Res; 77(7); 1510-41. ©2017 AACR.

A neutralized human LMP1-IgG inhibits ENKTL growth by suppressing the JAK3/STAT3 signaling pathway

Latent membrane protein 1 (LMP1), which is associated with the development of different types of Epstein-Barr virus (EBV) related lymphoma, has been suggested to be an important oncoprotein. In this study, a human anti-LMP1 IgG antibody (LMP1-IgG) was constructed and characterized by ELISA, western blotting (WB), affinity and immunohistochemistry (IHC) analyses. CCK-8, MTT, apoptosis assays, antibody-dependent cell-mediated cytotoxicity (ADCC) and CDC (complement-dependent cytotoxicity) assays were performed to evaluate the inhibitory effects of LMP1-IgG on extranodal nasal-type natural killer (NK)/T-cell lymphoma (ENKTL). Then, the influence of LMP1-IgG on the JAK/STAT signaling pathway was investigated. The results showed that the successfully constructed LMP1-IgG inhibited proliferation, induced apoptosis, and activated ADCC and CDC of ENKTL in a concentration- and time- dependent manner. Moreover, phosphorylation of JAK3 and STAT3 was inhibited by LMP1-IgG. Our data indicate that LMP1-IgG may provide a novel and promising therapeutic strategy for the treatment of LMP1-positive ENKTL.

Pediatric-type Follicular Lymphoma and Pediatric Nodal Marginal Zone Lymphoma: Recent Clinical, Morphologic, Immunophenotypic, and Genetic Insights

Pediatric-type follicular lymphoma and pediatric nodal marginal zone lymphoma are 2 of the rarest B-cell lymphomas. Although they are both predominantly seen in children, they can manifest in the adult population as well. Our understanding of these lymphomas has advanced rapidly in recent years such that we not only have a firm grasp of the morphologic and immunophenotypic findings, but also have a deeper insight into critical genetic and molecular pathways of these diseases. This review will cover the clinical and pathologic characteristics, treatment, prognosis, and important differential diagnoses of these entities.

The Microscope as a Tool for Disease Discovery-A Personal Voyage

This review reflects the trajectory of my career in hematopathology, and my personal reflections on scientific advances in the field. During the course of more than 40 years, the approach to classification of hematological malignancies has evolved from descriptive approaches, based on either cytological or clinical features, to a modern approach, which incorporates cutting-edge technologies. My philosophy has focused on defining individual diseases, an approach that can best lead to an understanding of molecular pathogenesis. To quote Carolus Linnaeus ( 1 , p. 19), the father of taxonomy, "The first step in wisdom is to know the things themselves; this notion consists in having a true idea of the objects; objects are distinguished and known by classifying them methodically and giving them appropriate names. Therefore, classification and name-giving will be the foundation of our science."

Molecular classification of tissue from a transformed non-Hogkin's lymphoma case with unexpected long-time remission

BACKGROUND

The concept of precision medicine in cancer includes individual molecular studies to predict clinical outcomes. In the present N = 1 case we retrospectively have analysed lymphoma tissue by exome sequencing and global gene expression in a patient with unexpected long-term remission following relaps. The goals were to phenotype the diagnostic and relapsed lymphoma tissue and evaluate its pattern. Furthermore, to identify mutations available for targeted therapy and expression of genes to predict specific drug effects by resistance gene signatures (REGS) for R-CHOP as described at http://www.hemaclass.org. We expected that such a study could generate therapeutic information and a frame for future individual evaluation of molecular resistance detected at clinical relapse.

CASE PRESENTATION

The patient was diagnosed with a transformed high-grade non-Hodgkin lymphoma stage III and treated with conventional R-CHOP [rituximab (R), cyclophosphamide (C), doxorubicin (H), vincristine (O) and prednisone (P)]. Unfortunately, she suffered from severe toxicity but recovered during the following 6 months' remission until biopsy-verified relapse. The patient refused second-line combination chemotherapy, but accepted 3 months' palliation with R and chlorambucil. Unexpectedly, she obtained continuous complete remission and is at present >9 years after primary diagnosis. Molecular studies and data evaluation by principal component analysis, mutation screening and copy number variations of the primary and relapsed tumor, identified a pattern of branched lymphoma evolution, most likely diverging from an in situ follicular lymphoma. Accordingly, the primary diagnosed transformed lymphoma was classified as a diffuse large B cell lymphoma (DLBCL) of the GCB/centrocytic subtype by "cell of origin BAGS" assignment and R sensitive and C, H, O and P resistant by "drug specific REGS" assignment. The relapsed DLBCL was classified as NC/memory subtype and R, C, H sensitive but O and P resistant.

CONCLUSIONS

Thorough analysis of the tumor DNA and RNA documented a branched evolution of the two clinical diagnosed tFL, most likely transformed from an unknown in situ lymphoma. Classification of the malignant tissue for drug-specific resistance did not explain the unexpected long-term remission and potential cure. However, it is tempting to consider the anti-CD20 immunotherapy as the curative intervention in the two independent tumors of this case.

Understanding the New WHO Classification of Lymphoid Malignancies: Why It's Important and How It Will Affect Practice

Improved delineation of lymphoid malignancy biology has prompted refinement of the 2008 World Health Organization (WHO) classification of hematopoietic and lymphoid tumors with a new framework introduced in 2016. This knowledge has provided valuable insights regarding management. Early clonal proliferations have been set apart given their limited potential for malignant dissemination. Increasing knowledge of molecular drivers of aggressive lymphomas has allowed subclassification and opportunity for clinical investigations to personalize therapy. New insights into T-cell pathophysiology has allowed grouping based on shared molecular and cellular features. This article will summarize the key changes in terms of diagnosis and histopathologic definitions, the impact of these changes on clinical management, and the challenges of future research in this field.

MGUS to myeloma: a mysterious gammopathy of underexplored significance

All cases of multiple myeloma (MM) are preceded by precursor states termed monoclonal gammopathy of undetermined significance (MGUS) or smoldering myeloma (SMM). Genetic analyses of MGUS cells have provided evidence that it is a genetically advanced lesion, wherein tumor cells carry many of the genetic changes found in MM cells. Intraclonal heterogeneity is also established early during the MGUS phase. Although the genetic features of MGUS or SMM cells at baseline may predict disease risk, transition to MM involves altered growth of preexisting clones. Recent advances in mouse modeling of MGUS suggest that the clinical dormancy of the clone may be regulated in part by growth controls extrinsic to the tumor cells. Interactions of MGUS cells with immune cells, bone cells, and others in the bone marrow niche may be key regulators of malignant transformation. These interactions involve a bidirectional crosstalk leading to both growth-supporting and inhibitory signals. Because MGUS is already a genetically complex lesion, application of new tools for earlier detection should allow delineation of earlier stages, which we term as pre-MGUS Analyses of populations at increased risk of MGUS also suggest the possible existence of a polyclonal phase preceding the development of MGUS. Monoclonal gammopathy in several patients may have potential clinical significance in spite of low risk of malignancy. Understanding the entire spectrum of these disorders may have broader implications beyond prevention of clinical malignancy.

A New Model to Study the Role of Arachidonic Acid in Colon Cancer Pathophysiology

A significant increase in cyclooxygenase 2 (COX2) gene expression has been shown to promote cylcooxygenase-dependent colon cancer development. Controversy associated with the role of COX2 inhibitors indicates that additional work is needed to elucidate the effects of arachidonic acid (AA)-derived (cyclooxygenase and lipoxygenase) eicosanoids in cancer initiation, progression, and metastasis. We have recently developed a novel Fads1 knockout mouse model that allows for the investigation of AA-dependent eicosanoid deficiency without the complication of essential fatty acid deficiency. Interestingly, the survival rate of Fads1-null mice is severely compromised after 2 months on a semi-purified AA-free diet, which precludes long-term chemoprevention studies. Therefore, in this study, dietary AA levels were titrated to determine the minimal level required for survival, while maintaining a distinct AA-deficient phenotype. Null mice supplemented with AA (0.1%, 0.4%, 0.6%, 2.0%, w/w) in the diet exhibited a dose-dependent increase (P < 0.05) in AA, PGE2, 6-keto PGF1α, TXB2, and EdU-positive proliferative cells in the colon. In subsequent experiments, null mice supplemented with 0.6% AA diet were injected with a colon-specific carcinogen (azoxymethane) in order to assess cancer susceptibility. Null mice exhibited significantly (P < 0.05) reduced levels/multiplicity of aberrant crypt foci (ACF) as compared with wild-type sibling littermate control mice. These data indicate that (i) basal/minimal dietary AA supplementation (0.6%) expands the utility of the Fads1-null mouse model for long-term cancer prevention studies and (ii) that AA content in the colonic epithelium modulates colon cancer risk. Cancer Prev Res; 9(9); 750-7. ©2016 AACR.

[Classification of malignant lymphomas. Current situation]

BACKGROUND

The World Health Organization (WHO) is planning an update of the WHO classification of malignant lymphomas.

OBJECTIVE

To present new findings concerning the diagnostics and subclassification of malignant lymphomas.

MATERIAL AND METHODS

A selective literature search ( http://www.ncbi.nlm.nih.gov ) was carried out and combined with the practical experiences of the authors in clinicopathological diagnostics.

RESULTS

In recent years an increasing number of early lesions of malignant lymphomas have been described but the potential malignancy of these lesions is at least for some entities still uncertain. Newly defined entities have been described within the group of T-cell lymphomas and prognostic subgroups have been identified in the heterogeneous group of diffuse large B-cell lymphomas. Detection of mutations facilitates the differential diagnostics of morphologically similar diseases and can be an important component of the diagnostics.

CONCLUSION

Recent scientific insights are being included more and more into the diagnostics of lymphomas. The update of the WHO classification is a consequence of these developments.

Peripheral T-Cell Lymphoma, Not Otherwise Specified and Concurrent Seminoma in Testis

Concurrent seminoma and malignant lymphoma of the testis is rare. We present a case of concurrent seminoma and peripheral T-cell lymphoma, not otherwise specified (PTCL-NOS) in a 54-year-old man who complained of painless left testicular enlargement. Radical left orchiectomy was performed. Macroscopically, the tumor (4.0 × 3.0 cm) was creamy, soft, and homogeneous, and microscopic evaluation revealed an alveolar structure of large cells that formed sheets, as well as colonization by other abnormal cells in a 1.0 × 1.0 cm area. The portion of the tumor comprising large abnormal cells was diagnosed as a seminoma, which was positive for c-kit by immunohistochemistry; the other portion was diagnosed as CD3/CD8, TIA, and granzyme B-positive PTCL-NOS. These two portions were clearly differentiated from one another. The patient received CHOP (cyclophosphamide, doxorubicin, vincristine, and prednisolone) therapy and achieved complete response for 50 months. To our knowledge, this is the first reported case of synchronous advanced seminoma and PTCL.

Lymphocytosis, lymphadenopathy: benign or malignant?

The increasing use of immunophenotypic and molecular analysis in the routine evaluation of patients with lymphocytosis, lymphadenopathy, or other hematologic disorders has led to the identification of unexpected small clonal lymphoid populations. These clones, sometimes with disease-specific markers, such as the t(14;18), are especially challenging for the clinician because of their unknown biologic potential and uncertain clinical behavior. Study of these early lymphoid lesions is providing important clues to the process of lymphomagenesis, and may provide the rationale for preemptive therapy in the future. More and more, the hematologist/oncologist is consulted regarding otherwise healthy individuals with lymphadenopathy and/or lymphocytosis, and pathology reports that confound the referring internist or surgeon. The report does not name a malignant lymphoproliferative disorder, but is not completely “normal”. Does the patient have a benign or malignant condition? How should they be evaluated? Is treatment indicated? These patients prove challenging for the consulting hematologist as well as the referring physician. In this review, we will focus on some of these scenarios and attempt to provide guidance for their management.

Is ALK-gene rearrangement overlooked in primary gastrointestinal T-cell lymphomas? About two cases

A 41-year-old male patient with a history of ankylosing spondylitis and Crohn disease, treated with immunomodulators and disease-modifying drugs, was diagnosed with a primary intestinal T-cell lymphoma that followed a 7.5-year-course. This transmural proliferation lacked cytological characteristics of anaplastic large cell lymphoma (ALCL), and was CD8-positive, and CD30- and anaplastic lymphoma kinase (ALK)-negative by immunohistochemistry (IHC). However, ALK-gene rearrangement (ALK-gr) was detected by fluorescence in situ hybridization (FISH) in both initial and persistent disease. The possibility of indolent T-cell lymphoproliferative disease of the gastrointestinal tract with atypical features (transmural involvement) related to ALK-gr was suggested. A previous case of aggressive 'enteropathy-associated ALCL' in the context of celiac disease was recently reported, which also lacked anaplastic morphology, and where CD30 and ALK expression was incidentally demonstrated by IHC, and ALK-gr subsequently confirmed by FISH. These two recent cases represent two distinct rare entities pertaining to the group of primary intestinal T-cell lymphomas, and they both show unexpected ALK-gr. This suggests that ALK-gr has been overlooked in the group of primary intestinal T-cell lymphomas. Performing IHC and FISH tests for ALK-gr in primary gastrointestinal T-cell lymphomas might be of importance, particularly with the advancement of targeted therapy that could impact treatment and prognosis.

Indolent cytotoxic T cell lymphoproliferation associated with nodular regenerative hyperplasia: a common liver lesion in the context of common variable immunodeficiency disorder

Patients with common variable immunodeficiency disorder (CVID) are subject to lymphoproliferative disorders and predisposed to lymphoma. Some patients may also develop liver lesions. The purpose of this study was to define clinical and histopathological features of patients with CVID presenting with liver lesions suspicious of lymphoma. Four CVID cases corresponding to these criteria were retrieved from our files. Liver biopsy specimens were subjected to morphologic, immunophenotypic and molecular analysis. All patients presented with hepatosplenomegaly and two furthermore with lymphadenopathy. The clinical working diagnosis in the four cases was lymphoma. All liver biopsies revealed nodular regenerative hyperplasia (NRH), associated with mild to marked sinusoid lymphocytic infiltrate consisting of "activated" cytotoxic T cells (CD8+, Tia1+, granzyme B+, TCRβF1+, CD56-). EBER was negative in all cases. T cell clonality was found in one of the two interpretable cases. All patients had an indolent course and clinical symptoms regressed with immunoglobulin replacement. This study suggests that indolent proliferation in the liver sinusoid of cytotoxic T cell associated with NRH is a specific liver lesion in the context of CVID. In CVID patients clinically suspected of lymphoma, pathologists should avoid a misdiagnosis of aggressive T cell lymphoma with a risk of over treatment.

The heterogeneity of follicular lymphomas: from early development to transformation

Follicular lymphoma (FL) is a lymphoma composed of germinal center B cells, i.e., centroblasts and centrocytes, that almost always show at least a focal follicular growth pattern. Most cases have a characteristic CD5-, CD10+, BCL6+, and BCL2+ immunophenotype, and 85 % of cases exhibit the hallmark translocation t(14;18)(q32;q21) involving BCL2 and IGH. Although the typical clinicopathological findings of FL are well recognized, cases with unusual clinical, morphologic, immunophenotypic, and genetic features may pose problems in diagnosis and nomenclature. In the slide workshop organized by the European Association for Haematopathology (EAHP) and the Society for Hematopathology (SH) held in Istanbul, Turkey, unusual variants of FL were discussed based on the submitted cases, including early lesions, localized extranodal presentation, uncommon immunophenotype, rare genetic alterations, diffuse variant, and marginal zone differentiation. Interesting features such as blastoid morphology and unusual progression forms were presented, aiming to understand the genetic basis of transformation. In this report, novel findings and diagnostic challenges emerging from the submitted cases will be highlighted, and new terminologies for some of these lesions are proposed.

ATP-binding cassette sub-family C member 4 (ABCC4) is overexpressed in human NK/T-cell lymphoma and regulates chemotherapy sensitivity: Potential as a functional therapeutic target

Nasal-type natural killer/T-cell (NK/T-cell) lymphomas are subtypes of non-Hodgkin's lymphoma (NHL), which are typically more clinically aggressive. There is, however relatively little understanding of nasal-type NK/T-cell lymphoma molecular pathogenesis. Thus, in this study we applied RNA sequencing to systematically screen for altered gene expression in human NK/T-cell lymphoma cell lines YTS and SNK-6 versus normal NK cells. We found that ATP-binding cassette sub-family C Member 4 (ABCC4) levels were significantly upregulated both in human NK/T-cell lymphoma YTS and SNK-6 cells, as compared with normal NK cells. These expression levels were further confirmed by real-time PCR. Protein levels of ABCC4 were also significantly higher in YTS and SNK-6 cells as compared with normal NK cells. Clinically relevant, ABCC4 expression levels were significantly higher in human NK/T-cell lymphoma tissues as compared with control nasal mucosa tissues, confirmed by immunohistochemical staining. In addition, we explored the biological function of such ABCC4 upregulation. Overexpression of ABCC4 by lentivirus transfection induced chemotherapy resistance to epirubicin (EPI) and cisplatin (DDP) in YTS cells. In contrast, knockdown of ABCC4 expression by shRNA contributed to chemotherapy sensitivity by both EPI and DDP. Furthermore, overexpression of ABCC4 inhibited, while downregulation of ABCC4 increased, YTS cell apoptosis following treatment by EPI or DDP. Therefore, the present study identified ABCC4 to be overexpressed in human NK/T-cell lymphoma cells, to regulate chemotherapy sensitivity to EPI and DDP, and possibly to be a functional therapeutic target. These findings may provide a basic rationale for new approaches in the effort to develop anti-tumor therapeutics for NK/T-cell lymphoma.

Skin Involvement of Mantle Cell Lymphoma May Mimic Primary Cutaneous Diffuse Large B-cell Lymphoma, Leg Type

Mantle cell lymphoma (MCL) is a B-cell neoplasm with a variable and generally aggressive clinical course. So far our knowledge of skin involvement of MCL is limited. To understand the clinical and histopathologic features of MCL with skin involvement, the files of the Lymph Node Registry Kiel were screened for MCL diagnosed in the skin. Over a period of 13 years, 1321 biopsy specimens were diagnosed as MCL; among them, 14 patients (1%) showed skin involvement. Of these, skin was the initial site of manifestation in 6/11 (55%) cases. One patient presented with a skin-limited lymphoma. Furthermore, 7/12 (58%) patients presented with lesions on the leg. The lymphomas were highly proliferative with blastoid cytology in 12/14 (86%) cases. Moreover, the immunophenotype with expression of BCL2 (100%), MUM-1/IRF4 (83%), and IgM (82%) and lack of CD10 (25%) and BCL6 (0%) closely resembled the features of primary cutaneous diffuse large B-cell lymphoma, leg type. Solely the expression of cyclin D1 (100%) and the presence of t(11;14) (100%) allowed a distinction from cases of primary cutaneous diffuse large B-cell lymphoma, leg type. Only 2 MCL cases with skin involvement presented with classical cytology. Interestingly, in these 2 cases skin involvement occurred simultaneously in a lesion of coexisting primary cutaneous marginal zone lymphoma. Our data suggest that clinical presentation on the leg and blastoid cytology along with high proliferation and expression of Bcl2, Mum-1/IRF4, and IgM are typical for MCL involving the skin. Lymphomas with these features might be erroneously diagnosed as diffuse large B-cell lymphoma, leg type, if cyclin D1 staining is not performed.

Atypical Marginal Zone Hyperplasia Is a Mimic for Lymphoma in Pediatric Transplant Recipients: Report of Two Patients

Atypical marginal zone hyperplasia (AMZH) of mucosa-associated lymphoid tissue (MALT) closely resembles lymphoma in that it shows expansion of the marginal zones with prominent intraepithelial B lymphocytes, is immunoglobulin light-chain restricted, and may show aberrant CD43 expression. However, unlike lymphoma, it does not show rearrangement of the immunoglobulin heavy chain gene (immunoglobulin H [IgH]) by polymerase chain reaction (PCR), and it behaves in a benign fashion. We identified AMZH in 2 pediatric solid organ transplant recipients who presented with adenotonsillar hypertrophy. To date, the patients have experienced a self-limited course in the absence of treatment or reduction of immunosuppression. Atypical marginal zone hyperplasia is a pitfall for posttransplant lymphoproliferative disorder and MALT lymphoma in the pediatric solid organ transplant population. In transplant patients with a lambda-restricted B-cell clone and marginal zone hyperplasia in native MALT sites, PCR for IgH and IgK gene rearrangement is essential to prevent misdiagnosis.