Expression of CXCL13, a chemokine highly upregulated in germinal center T-helper cells, distinguishes angioimmunoblastic T-cell lymphoma from peripheral T-cell lymphoma, unspecified

Biological insights into the role of TET2 in T cell lymphomas

Peripheral T cell lymphomas (PTCL) are a heterogenous group of mature T cell lymphomas with an overall poor prognosis. Understanding the molecular heterogeneity in PTCL subtypes may lead to improved understanding of the underlying biological mechanisms driving these diseases. Mutations in the epigenetic regulator TET2 are among the most frequent mutations identified in PTCL, with the highest frequency in angioimmunoblastic T cell lymphomas and other nodal T follicular helper (TFH) lymphomas. This review dissects the role of TET2 in nodal TFH cell lymphomas with a focus on emerging biological insights into the molecular mechanism promoting lymphomagenesis and the potential for epigenetic therapies to improve clinical outcomes.

Role of cytokine in malignant T-cell metabolism and subsequent alternation in T-cell tumor microenvironment

T cells are an important component of adaptive immunity and T-cell-derived lymphomas are very complex due to many functional sub-types and functional elasticity of T-cells. As with other tumors, tissues specific factors are crucial in the development of T-cell lymphomas. In addition to neoplastic cells, T- cell lymphomas consist of a tumor micro-environment composed of normal cells and stroma. Numerous studies established the qualitative and quantitative differences between the tumor microenvironment and normal cell surroundings. Interaction between the various component of the tumor microenvironment is crucial since tumor cells can change the microenvironment and vice versa. In normal T-cell development, T-cells must respond to various stimulants deferentially and during these courses of adaptation. T-cells undergo various metabolic alterations. From the stage of quiescence to attention of fully active form T-cells undergoes various stage in terms of metabolic activity. Predominantly quiescent T-cells have ATP-generating metabolism while during the proliferative stage, their metabolism tilted towards the growth-promoting pathways. In addition to this, a functionally different subset of T-cells requires to activate the different metabolic pathways, and consequently, this regulation of the metabolic pathway control activation and function of T-cells. So, it is obvious that dynamic, and well-regulated metabolic pathways are important for the normal functioning of T-cells and their interaction with the microenvironment. There are various cell signaling mechanisms of metabolism are involved in this regulation and more and more studies have suggested the involvement of additional signaling in the development of the overall metabolic phenotype of T cells. These important signaling mediators include cytokines and hormones. The impact and role of these mediators especially the cytokines on the interplay between T-cell metabolism and the interaction of T-cells with their micro-environments in the context of T-cells lymphomas are discussed in this review article.

Follicular helper T-cell lymphomas: disease spectrum, relationship with clonal hematopoiesis, and mimics. A report of the 2022 EA4HP/SH lymphoma workshop

Follicular helper T-cell lymphomas (TFH lymphomas) were discussed in session V of the lymphoma workshop of the European Association for Haematopathology (EA4HP)/Society for Hematopathology (SH) 2022 meeting in Florence, Italy. The session focused on the morphologic spectrum of TFH lymphoma, including its three subtypes: angioimmunoblastic-type (AITL), follicular-type, and not otherwise specified (NOS). The submitted cases encompassed classic examples of TFH lymphoma and unusual cases such as those with early or indolent presentations, associated B-cell proliferations, or Hodgkin/Reed-Sternberg-like cells. The relationship between TFH lymphoma and clonal hematopoiesis was highlighted by several cases documenting divergent evolution of myeloid neoplasm and AITL from shared clonal mutations. The distinction between TFH lymphoma and peripheral T-cell lymphoma, not otherwise specified (PTCL, NOS), was stressed, and many challenging examples were presented. Various cases highlighted the difficulties of differentiating TFH lymphoma from other established types of lymphoma and reactive conditions. Cutaneous T-cell lymphoma expressing TFH markers, particularly when resulting in lymph node involvement, should be distinguished from TFH lymphomas. Additional immunophenotyping and next-generation sequencing studies were performed on various cases in this session, highlighting the importance of these technologies to our current understanding and classification of TFH lymphomas.

Misdiagnosis of angioimmunoblastic T‑cell lymphoma: A case report

Angioimmunoblastic T-cell lymphoma (AITL) is a specific subtype of peripheral T-cell lymphoma that is challenging to diagnose due to the lack of specific pathological characteristics. This report describes the case of a 56-year-old man with Hodgkin lymphoma in whom the gene rearrangement results were positive for TCRβDB+Jβ1/2. Pathological and immunochemical examinations revealed a diagnosis of lymphoma that was a composite of AITL and focal classical Hodgkin lymphoma. Unfortunately, he died soon after the correct diagnosis was made. This case shows that a combination of immunohistochemistry and gene rearrangement analysis can increase the diagnostic accuracy for AITL. A review of the literature on the misdiagnosis of AITL indicates that this disease progresses rapidly with a high mortality rate. Our experience, in this case, highlights the need for early diagnosis.

Angioimmunoblastic T-cell lymphoma and correlated neoplasms with T-cell follicular helper phenotype: from molecular mechanisms to therapeutic advances

Angioimmunoblastic T-cell lymphoma (AITL) is the second most frequent subtype of mature T-cell lymphoma (MTCL) in the Western world. It derives from the monoclonal proliferation of T-follicular helper (TFH) cells and is characterized by an exacerbated inflammatory response and immune dysregulation, with predisposition to autoimmunity phenomena and recurrent infections. Its genesis is based on a multistep integrative model, where age-related and initiator mutations involve epigenetic regulatory genes, such as TET-2 and DNMT3A. Subsequently, driver-mutations, such as RhoA G17V and IDH-2 R172K/S promote the expansion of clonal TFH-cells ("second-hit"), that finally begin to secrete cytokines and chemokines, such as IL-6, IL-21, CXCL-13 and VEGF, modulating a network of complex relationships between TFH-cells and a defective tumor microenvironment (TME), characterized by expansion of follicular dendritic cells (FDC), vessels and EBV-positive immunoblasts. This unique pathogenesis leads to peculiar clinical manifestations, generating the so-called "immunodysplastic syndrome", typical of AITL. Its differential diagnosis is broad, involving viral infections, collagenosis and adverse drug reactions, which led many authors to use the term "many-faced lymphoma" when referring to AITL. Although great advances in its biological knowledge have been obtained in the last two decades, its treatment is still an unmet medical need, with highly reserved clinical outcomes. Outside the setting of clinical trials, AITL patients are still treated with multidrug therapy based on anthracyclines (CHOP-like), followed by up-front consolidation with autologous stem cell transplantation (ASCT). In this setting, the estimated 5-year overall survival (OS) is around 30-40%. New drugs, such as hypomethylating agents (HMAs) and histone deacetylase inhibitors (HDAi), have been used for relapsed/refractory (R/R) disease with promising results. Such agents have their use based on a biological rationale, have significant potential to improve the outcomes of patients with AITL and may represent a paradigm shift in the therapeutic approach to this lymphoma in the near future.

RHOA G17V induces T follicular helper cell specification and involves angioimmunoblastic T-cell lymphoma via upregulating the expression of PON2 through an NF-κB-dependent mechanism

Angioimmunoblastic T-cell lymphoma (AITL) is a malignant hematologic tumor arising from T follicular helper (Tfh) cells. High-throughput genomic sequencing studies have shown that AITL is characterized by a novel highly recurring somatic mutation in RHOA, encoding p.Gly17Val (RHOA G17V). However, the specific role of RHOA G17V in AITL remains unknown. Here, we demonstrated that expression of Rhoa G17V in CD4⁺ T cells increased cell proliferation and induces Tfh cell specification associated with Pon2 upregulation through an NF-κB-dependent mechanism. Further, loss of Pon2 attenuated oncogenic function induced by genetic lesions in Rhoa. In addition, an abnormality of RHOA G17V mutation and PON2 expression is also detected in patients with AITL. Our findings suggest that PON2 associated with RHOA G17V mutation might control the direction of the molecular agents-based AITL and provide a new therapeutic target in AITL.

Human Germinal Center-associated Lymphoma (HGAL) Is a Reliable Marker of Normal and Neoplastic Follicular Helper T Cells Including Angioimmunoblastic T-Cell Lymphoma

The diagnosis of angioimmunoblastic T-cell lymphoma (AITL) is complex and requires the demonstration of a T-follicular helper (TFH) phenotype. Immunophenotypic markers that detect the TFH phenotype are highly variable, thereby necessitating the use of 3 to 5 TFH markers to substantiate a TFH phenotype. We tested the utility of germinal center markers human germinal center-associated lymphoma (HGAL) and LIM-domain only 2 (LMO2) in detecting a TFH phenotype. We compared their staining to that of 6 TFH markers in current use, PD-1, ICOS, CXCL13, SAP, CD10, and BCL6, in a cohort of 23 AITL. Our results show that although both markers can detect a TFH phenotype, HGAL was superior to LMO2 in the percent of cells stained and the intensity of staining, 2 variables used to generate H-scores. Using H-scores as the metric, HGAL was most comparable to BCL6 among the currently used TFH markers and was more sensitive than CXCL13, SAP, CD10, and LMO2. PD-1 and ICOS emerged as the most robust of the 8 markers tested in this study in detecting a TFH phenotype. We conclude that HGAL is a reliable marker of TFH cells and can aid in the diagnosis of lymphomas of TFH derivation, particularly in the recognition of early patterns of AITL.

The lymph node transcriptome of unicentric and idiopathic multicentric Castleman disease

Castleman disease is a polyclonal lymphoproliferative disorder characterized by unicentric or multicentric lymphadenopathy with characteristic histomorphological features, in addition to variable inflammatory symptomatology. The molecular mechanisms and etiologies of unicentric Castleman disease (UCD) and idiopathic multicentric Castleman disease (iMCD) are poorly understood, and identification of targetable disease mediators remains an unmet clinical need. We performed whole exome sequencing on lymph node biopsies from patients with UCD and iMCD and compared the transcriptomic profiles to that of benign control lymph nodes. We identified significantly upregulated genes in UCD (n=443), iMCD (n=316) or both disease subtypes (n=51) and downregulated genes in UCD (n=321), iMCD (n=105) or both (n=10). The transcriptomes of UCD and iMCD showed enrichment and upregulation of elements of the complement cascade. By immunohistochemistry, C4d deposits indicative of complement activation were found to be present in UCD and iMCD, mostly within abnormally regressed germinal centers, but also in association with plasma cell clusters, endothelial cells and stroma cell proliferations. Other enriched gene sets included collagen organization, S1P3 pathway and VEGFR pathway in UCD; and humoral response, oxidative phosphorylation and proteosome in iMCD. Analysis of cytokine transcripts showed upregulation of CXCL13 but not IL6 in UCD and iMCD. Among angiogenic mediators, the VEGFR1 ligand placental growth factor (PGF) was upregulated in both disease subtypes. We hereby report for the first time the whole lymph node transcriptomes of UCD and iMCD, underscoring findings that could aid in the discovery of targetable disease mediators.

T-Cell Lymphomas, Version 2.2022, NCCN Clinical Practice Guidelines in Oncology

Peripheral T-cell lymphomas (PTCLs) are a heterogeneous group of lymphoproliferative disorders arising from mature T cells, accounting for about 10% of non-Hodgkin lymphomas. PTCL-not otherwise specified is the most common subtype, followed by angioimmunoblastic T-cell lymphoma, anaplastic large cell lymphoma, anaplastic lymphoma kinase-positive, anaplastic large cell lymphoma, anaplastic lymphoma kinase-negative, and enteropathy-associated T-cell lymphoma. This discussion section focuses on the diagnosis and treatment of PTCLs as outlined in the NCCN Guidelines for T-Cell Lymphomas.

Markers of Follicular Helper T Cells Are Occasionally Expressed in T-Cell or Histiocyte-Rich Large B-Cell Lymphoma, Classic Hodgkin Lymphoma, and Atypical Paracortical HyperplasiaA Diagnostic Pitfall For T-Cell Lymphomas of T Follicular Helper Origin

OBJECTIVES

Follicular helper T cell (TFH) markers are expressed in angioimmunoblastic T-cell lymphoma (AITL) and peripheral T-cell lymphoma of the TFH phenotype (PTCL-TFH). However, differential expression and coexpression of these markers in benign and other malignant lymphoid proliferations have not been well studied.

METHODS

We performed programmed death-1 (PD-1), C-X-C motif chemokine ligand 13 (CXCL13), inducible costimulator (ICOS), CD10, and B-cell lymphoma 6 protein (BCL-6) immunohistochemistry on AITL, PTCL not otherwise specified (PTCL-NOS), PTCL-TFH, T-cell or histiocyte-rich large B-cell lymphoma (THRLBCL), classic Hodgkin lymphoma (CHL), atypical paracortical hyperplasia (PCH), progressive transformation of germinal centers (PTGC), and reactive follicular hyperplasia (RFH).

RESULTS

CXCL13 and ICOS were more sensitive but less specific for AITL than PD-1, CD10, and BCL-6. Moreover, 74% of AITL (none of PTCL-NOS or PTCL-TFH) coexpressed more than 2 TFH markers. In background T cells of THRLBCL, 70% of cases coexpressed more than 1 marker. The background T cells of CHL expressed all TFH markers except CD10 in all cases. In addition, 13% of PCH cases coexpressed more than 1 marker. In RFH and PTGC, all markers were expressed mainly in germinal centers with rare extrafollicular staining.

CONCLUSIONS

AITL, PTCL-NOS, and PTCL-TFH show differential expression of TFH markers. AITL frequently coexpresses more than 2 TFH markers. TFH markers can be expressed in PCH and in background T cells of THRLBCL and CHL. Consequently, caution should be used before a diagnosis of AITL is established, particularly with limited samples.

Management of Angioimmunoblastic T-Cell Lymphoma (AITL) and other T Follicular Helper Cell lymphomas (TFH PTCL)

Despite the remarkable improvements in the treatment and outcome of patients with aggressive B-cell lymphoma, the peripheral T-cell lymphomas (PTCL) continue to carry a poor prognosis with the presently available treatment options. The PTCL are very rare diseases that account for only 10,000 to 15,000 new cases per year in the United States. The World Health Organization's 2016 classification describes 29 distinct subtypes of PTCL, thus making these both rate and incredibly heterogenous. The 2 most common forms of PTCL, for example, peripheral T-cell lymphoma-not otherwise specified and angioimmunoblastic T-cell lymphoma , have an incidence of only 2500 and 1800 cases per year respectively, in the United States.

The new biology of PTCL-NOS and AITL: current status and future clinical impact

Peripheral T-cell lymphomas (PTCL) comprise a heterogeneous group of aggressive lymphoproliferative disorders almost all of which are associated with poor clinical outcomes. Angioimmunoblastic T-cell lymphoma (AITL) and some peripheral T-cell lymphoma, not otherwise specified (PTCL-NOS) have similarities to normal CD4⁺ T-cell subsets in their gene expression profiles. A cell of origin model is, therefore, emerging and is likely to be refined in the future. Follicular helper (Tfh) T cells are now established as the cell of origin of AITL and about 20% of PTCL-NOS. Sequencing studies have identified recurrent genetic alterations in epigenetic modifiers, T-cell receptor signalling pathway intermediates or RHOA, most commonly a specific mutation leading to RHOA G17V. While PTCL-NOS remains a diagnosis of exclusion, advances in genomics have identified subgroups expressing transcription factors TBX 21 (Th1-like origin) and GATA3 (Th2-like origin). These findings suggest new biomarkers and new therapeutic avenues including the hypomethylating agent azacytidine, or inhibitors of proximal T-cell receptor (TCR) signalling and potentially certain monoclonal antibodies. The advances over the past few years, therefore, prompt stratified medicine approaches to test biologically based treatments and determine the clinical utility of the new disease classifications.

GAPDH Overexpression in the T Cell Lineage Promotes Angioimmunoblastic T Cell Lymphoma through an NF-κB-Dependent Mechanism

GAPDH is emerging as a key player in T cell development and function. To investigate the role of GAPDH in T cells, we generated a transgenic mouse model overexpressing GAPDH in the T cell lineage. Aged mice developed a peripheral Tfh-like lymphoma that recapitulated key molecular, pathological, and immunophenotypic features of human angioimmunoblastic T cell lymphoma (AITL). GAPDH induced non-canonical NF-κB pathway activation in mouse T cells, which was strongly activated in human AITL. We developed a NIK inhibitor to reveal that targeting the NF-κB pathway prolonged AITL-bearing mouse survival alone and in combination with anti-PD-1. These findings suggest the therapeutic potential of targeting NF-κB signaling in AITL and provide a model for future AITL therapeutic investigations.

Cutaneous localization of angioimmunoblastic T-cell lymphoma may masquerade as B-cell lymphoma or classical Hodgkin lymphoma: A histologic diagnostic pitfall

BACKGROUND

We report the cases of three patients presenting skin lesions whose biopsies showed nodular polymorphic infiltrates consisting of lymphocytes, plasma cells, histiocytes, eosinophils, B blasts, and Hodgkin Reed-Sternberg (HRS)-like cells. Two of them were initially diagnosed as classical Hodgkin lymphoma (cHL), on the other hand, the last one as a B-cell lymphoma. All patients have been treated for angioimmunoblastic T-cell lymphoma (AITL).

METHODS

We performed a second review of the skin biopsies with further immunophenotypic molecular analyses. Scrupulous observation revealed, in the background of the three cases, atypical small to medium-sized lymphocytes carrying a CD3+, CD4+ T-cell phenotype and expressing PD1 and CXCL13 follicular helper T-cell markers. The two lesions initially diagnosed as cHL showed scattered HRS-like cells with CD30+, CD15+, PAX5+, CD20-, Epstein Barr Virus (EBV) + classical phenotype. The case initially diagnosed as B-cell lymphoma showed a diffuse B-cell proliferation associated with small B-cell and medium to large-sized B blasts that were positive for EBV.

CONCLUSION

Those cases highlighted that atypical T-cells may be obscured by B-cell proliferation mimicking cHL or B-cell lymphoma in cutaneous localization of AITL and confirmed the requirement of collecting clinical information before performing a diagnosis.

B2 microglobulin is a novel prognostic marker of Angioimmunoblastic T-cell lymphoma

The aim of the present study was to analyze features and explore parameters that can help to predict prognosis for angioimmunoblastic T-cell lymphoma (AITL). A total of 117 patients with AITL were retrospectively analyzed. Multivariate analysis showed that β2 microglobulin (β2-M) ≥4.0 mg/L (P = 0.020), rash/pruritus (P = 0.004), performance status (PS) ≥2 (P = 0.006), age >60 years (P = 0.006) and extranodal sites (ENSs) >1 (P = 0.029) were independent risk factors for OS. Rash/pruritus (P = 0.007), age >60 years (P = 0.035) and ENSs >1 (P = 0.006) were independent risk factors for PFS. A novel prognostic model consisting of β2-M, rash/pruritus, PS, age and ENSs >1 was constructed. The model classified patients into 3 risk stratifications: low risk (0 or 1 factor), intermediate risk (2 factors), high risk (≥3 factors) and significantly stratified patients with AITL (P < 0.001). In conclusion, except for PS ≥2, age >60 years and ENSs >1 used in IPI, β2-M and rash/pruritus also indicated adverse prognosis. That we constructed model was commendably prognostic for OS and PFS.

Insights Into the Molecular Mechanisms of T Follicular Helper-Mediated Immunity and Pathology

T follicular helper (Tfh) cells play key role in providing help to B cells during germinal center (GC) reactions. Generation of protective antibodies against various infections is an important aspect of Tfh-mediated immune responses and the dysregulation of Tfh cell responses has been implicated in various autoimmune disorders, inflammation, and malignancy. Thus, their differentiation and maintenance must be closely regulated to ensure appropriate help to B cells. The generation and function of Tfh cells is regulated by multiple checkpoints including their early priming stage in T zones and throughout the effector stage of differentiation in GCs. Signaling pathways activated downstream of cytokine and costimulatory receptors as well as consequent activation of subset-specific transcriptional factors are essential steps for Tfh cell generation. Thus, understanding the mechanisms underlying Tfh cell-mediated immunity and pathology will bring into spotlight potential targets for novel therapies. In this review, we discuss the recent findings related to the molecular mechanisms of Tfh cell differentiation and their role in normal immune responses and antibody-mediated diseases.

Angioimmunoblastic T-cell lymphoma: a prognostic model from a retrospective study

Angioimmunoblastic T-cell lymphoma (AITL) is a distinct subtype of peripheral T-cell lymphoma with unique clinical and pathological features. This study aim to design a prognostic model specifically for AITL, providing risk stratification in affected patients. A total of 115 newly diagnosed AITL patients were retrospectively analyzed. The estimated five-year overall survival (OS) rate for all patients was 45.4%. Multivariate analysis found prognostic factors for survival were bone marrow involvement, number of extranodal sites >1, and performance status >1. We categorized three risk groups: group 1, no adverse factor; group 2, one factor; and group 3, two or three factors. Five-year OS was 86.9% for Group 1, 46.3% for Group 2, and 16.2% for Group 3 (p < .0001). The novel prognostic model balanced the distribution of patients into different risk groups with better predictive discrimination as compared to the International Prognostic Index and Prognostic Index for PTCL, unless otherwise specified.

RHOA G17V Induces T Follicular Helper Cell Specification and Promotes Lymphomagenesis

Angioimmunoblastic T cell lymphoma (AITL) is an aggressive tumor derived from malignant transformation of T follicular helper (Tfh) cells. AITL is characterized by loss-of-function mutations in Ten-Eleven Translocation 2 (TET2) epigenetic tumor suppressor and a highly recurrent mutation (p.Gly17Val) in the RHOA small GTPase. Yet, the specific role of RHOA G17V in AITL remains unknown. Expression of Rhoa G17V in CD4⁺ T cells induces Tfh cell specification; increased proliferation associated with inducible co-stimulator (ICOS) upregulation and increased phosphoinositide 3-kinase (PI3K) and mitogen-activated protein kinase signaling. Moreover, RHOA G17V expression together with Tet2 loss resulted in development of AITL in mice. Importantly, Tet2^-/-RHOA G17V tumor proliferation in vivo can be inhibited by ICOS/PI3K-specific blockade, supporting a driving role for ICOS signaling in Tfh cell transformation.

The curious origins of angioimmunoblastic T-cell lymphoma

PURPOSE OF REVIEW

Once an obscure disease, recent studies have transformed our understanding of angioimmunoblastic T-cell lymphoma (AITL). In this review, we summarize new major advances in the genetics and biology of AITL.

RECENT FINDINGS

Genome wide sequencing studies have dissected the repertoire of the genetic alterations driving AITL uncovering a highly recurrent Gly17Val somatic mutation in the small GTPase RHOA and major role for mutations in epigenetic regulators, such as TET2, DNMT3A and IDH2, and signaling factors (e.g., FYN and CD28). These findings support a multistep model of follicular T helper cell transformation in AITL and pinpoint novel candidates for the development of targeted therapies in this disease.

SUMMARY

AITL originates from follicular T helper cells and is characterized by the presence of RHOA G17V mutation together with genetic alterations in TET2, DNMT3A, and IDH2. Research efforts now focus on the elucidation of the specific roles and interplay of these genetic alterations in the pathogenesis of AITL.

The Diagnosis, Management, and Role of Hematopoietic Stem Cell Transplantation in Aggressive Peripheral T-Cell Neoplasms

Background

Peripheral T-cell neoplasms (PTCNs) comprise a group of uncommon and heterogeneous lymphoid malignancies. They are more difficult to diagnose and treat and have a worse prognosis than B-cell lymphomas. Although PTCNs initially show a significant degree of chemosensitivity, the outcome of treatment with conventional dose chemotherapy remains poor.

Methods

We reviewed the literature on the diagnosis, treatment, and collective transplant reports regarding PTCNs.

Results

The correct diagnosis of peripheral T-cell lymphoma requires a combination of clinical presentation, morphology, immunophenotype, and molecular study. While no specific treatment other than conventional dose chemotherapy is currently available for aggressive PTCN, histone acetylase inhibitors and monoclonal antibodies such as anti-CD7 and anti-CD52 are being studied in T-cell malignancies. The role of autologous and allogeneic transplantation is being investigated for high-risk, relapsed, and refractory PTCNs with some promising results.

Conclusions

Access to hematopathology expertise in a tertiary care setting may lead to earlier and more accurate diagnoses of these diseases. PTCNs comprise a heterogeneous group of diseases with no widely accepted standard of care, and accurate determination of their histologic subtypes correlates with prognosis. Patients in first complete remission with poor risk features and patients with relapsed and refractory disease should be considered for bone marrow transplant due to the poor outcomes obtained with conventional chemotherapy.

A Clinicopathologic Study of Lennert Lymphoma and Possible Prognostic Factors: The Importance of Follicular Helper T-cell Markers and the Association With Angioimmunoblastic T-cell Lymphoma

Lennert lymphoma (LeL) is a variant of peripheral T-cell lymphoma, not otherwise specified. Few clinicopathologic studies have investigated LeL, which is a rare disease. Here, we analyzed the clinicopathologic features of 26 patients with LeL to identify potential prognostic factors. Neoplastic cells positive for CD4, CD8, CD4/CD8, TIA-1, and granzyme B were observed in 21 (80.8%), 4 (15.4%), 1 (3.8%), 4 (15.3%), and 0 (0.0%) patients, respectively. Regarding follicular helper T-cell (TFH) markers, neoplastic cells positive for programmed cell death-1 (PD-1), CXCL13, CD10, and BCL6 were observed in 14 (53.8%), 13 (50.0%), 1 (3.8%), and 0 (0.0%) patients, respectively. Patients with positivity for at least 1 TFH cell marker (PD-1, CXCL13, CD10, and/or BCL6) were defined as being TFH cell marker-positive (n=15) and had a worse prognosis than TFH cell marker-negative patients (n=11) (P=0.011). Clinicopathologic characteristics did not differ significantly between TFH cell marker-positive and marker-negative LeL patients. Moreover, prognosis did not differ significantly between TFH cell marker-positive LeL patients and patients with angioimmunoblastic T-cell lymphoma (AITL) (n=42). Nevertheless, as compared with AITL, TFH cell marker-positive LeL was associated with significantly lower frequencies of B symptoms, skin rash, high-intermediate-risk or high-risk international prognostic index values, expanded follicular dendritic cell meshworks, polymorphic infiltrate, clear cells, and positivity for CD10 and BCL6. Although it may be difficult to definitively distinguish between TFH cell marker-positive LeL and AITL, our results suggest that TFH cell markers are useful for identifying LeL patients who will experience unfavorable outcomes.

The role of follicular T helper cells in patients with malignant lymphoid disease

OBJECTIVES

To investigate the dynamic change of follicular T helper cells (T_FH) in patients with malignant lymphoid disease (MLD) and to explore its clinical significance.

METHODS

The dynamic change of T_FH cells, ICOS⁺- and PD-1⁺ T_FH cells at pretreatment and different treatment periods was determined by flow cytometry in 85 MLD patients. Concentration of interleukin 21 (IL-21) was evaluated by ELISA, and the correlation between clinical prognosis and the ratio of T_FH cells was analyzed.

RESULTS

Significantly increased ICOS⁺- and PD-1⁺ T_FH cells were found in MLD patients at pretreatment compared to healthy controls. Decreased or even close to normal levels of ICOS⁺- and PD-1⁺ T_FH cells were found at the end of treatment. However, in the patients with progressive disease, high levels of ICOS⁺- and PD-1⁺ T_FH cells were found. Moreover, a significantly increased plasma IL-21 level was found in MLD patients. Negative correlation was found between the level of ICOS⁺-, PD-1⁺ T_FH cells, as well as IL-21 and the prognosis of MLD.

CONCLUSIONS

Significantly increased T_FH cell ratios were found in patients with MLD, and decreased T_FH cells ratios could be expected in those treatment-effective patients, which could be used as the therapeutic efficacy index.

T cell-rich lymphoid infiltrates with large B cells: a review of key entities and diagnostic approach

Accurate diagnostic interpretation of a lymphoid population composed predominantly of small T cells, together with smaller numbers of large B cells, with or without a nodular architecture, is a common problem faced by the histopathologist. The differential diagnosis of this histological pattern is wide, ranging from reactive conditions such as drug reactions and viral infections, through borderline entities such as immunodeficiency-related lymphoproliferative disorders to lymphomas. The latter includes entities where the large B cells are primarily neoplastic (classical and nodular lymphocyte-predominant Hodgkin lymphomas and T cell/histiocyte-rich large B cell lymphoma) as well as T cell lymphomas such as angioimmunoblastic T cell lymphoma where the large B cells represent an epiphenomenon and may or may not be neoplastic. Several rare variants of these conditions, and the fact that treatment can significantly modify appearances, add to the diagnostic difficulty of these pathological entities. Unlike monomorphic lymphoid infiltrates, the histological pattern of T cell-rich proliferation with large B cells requires close evaluation of the inter-relationship between B cells and T cells, follicular dendritic cells and sometimes other inflammatory cells. Epstein-Barr virus plays a key role in several of these scenarios, and interpreting not only its presence but also its distribution within cellular subgroups is essential to accurate diagnosis and the avoidance of some important diagnostic pitfalls. An understanding of normal immunoarchitecture and lymphoid maturational pathways is also fundamental to resolving these cases, as is a knowledge of their common patterns of spread, which facilitates correlation with clinical and radiological findings.

T-cell lymphomas, a challenging disease: types, treatments, and future

T-cell lymphomas are rare and aggressive malignancies associated with poor outcome, often because of the development of resistance in the lymphoma against chemotherapy as well as intolerance in patients to the established and toxic chemotherapy regimens. In this review article, we discuss the epidemiology, pathophysiology, current standard of care, and future treatments of common types of T-cell lymphomas, including adult T-cell leukemia/lymphoma, angioimmunoblastic T-cell lymphoma, anaplastic large-cell lymphoma, aggressive NK/T-cell lymphoma, and cutaneous T-cell lymphoma.

Peripheral T-cell lymphomas of follicular helper T-cell type frequently display an aberrant CD3(-/dim)CD4(+) population by flow cytometry: an important clue to the diagnosis of a Hodgkin lymphoma mimic

Nodal follicular helper T-cell-derived lymphoproliferations (specifically the less common peripheral T-cell lymphomas of follicular type) exhibit a spectrum of histologic features that may mimic reactive hyperplasia or Hodgkin lymphoma. Even though angioimmunoblastic T-cell lymphoma and peripheral T-cell lymphoma of follicular type share a common biologic origin from follicular helper T-cells and their morphology has been well characterized, flow cytometry of peripheral T-cell lymphomas of follicular type has not been widely discussed as a tool for identifying this reactive hyperplasia/Hodgkin lymphoma mimic. We identified 10 peripheral T-cell lymphomas of follicular type with available flow cytometry data from five different institutions, including two cases with peripheral blood evaluation. For comparison, we examined flow cytometry data for 8 classical Hodgkin lymphomas (including 1 lymphocyte-rich classical Hodgkin lymphoma), 15 nodular lymphocyte predominant Hodgkin lymphomas, 15 angioimmunoblastic T-cell lymphomas, and 26 reactive nodes. Lymph node histology and flow cytometry data were reviewed, specifically for the presence of a CD3(-/dim)CD4(+) aberrant T-cell population (described in angioimmunoblastic T-cell lymphomas), besides other T-cell aberrancies. Nine of 10 (90%) peripheral T-cell lymphomas of follicular type showed a CD3(-/dim)CD4(+) T-cell population constituting 29.3% (range 7.9-62%) of all lymphocytes. Five of 10 (50%) had nodular lymphocyte predominant Hodgkin lymphoma or lymphocyte-rich classical Hodgkin lymphoma-like morphology with scattered Hodgkin-like cells that expressed CD20, CD30, CD15, and MUM1. Three cases had a nodular growth pattern and three others exhibited a perifollicular growth pattern without Hodgkin-like cells. Epstein-Barr virus was positive in 1 of 10 cases (10%). PCR analysis showed clonal T-cell receptor gamma gene rearrangement in all 10 peripheral T-cell lymphomas of follicular type. By flow cytometry, 11 of 15 (73.3%) angioimmunoblastic T-cell lymphomas showed the CD3(-/dim)CD4(+) population (mean: 19.5%, range: 3-71.8%). Using a threshold of 3% for CD3(-/dim)CD4(+) T cells, all 15 nodular lymphocyte predominant Hodgkin lymphoma controls and 8 classical Hodgkin lymphomas were negative (Mann-Whitney P=0.01, F-PTCL vs Hodgkin lymphomas), as were 25 of 26 reactive lymph nodes. The high frequency of CD3(-/dim)CD4(+) aberrant T cells is similar in angioimmunoblastic T-cell lymphomas and peripheral T-cell lymphomas of follicular type, and is a useful feature in distinguishing peripheral T-cell lymphomas of follicular type from morphologic mimics such as reactive hyperplasia or Hodgkin lymphoma.

Long non-coding RNA MEG3 inhibits microRNA-125a-5p expression and induces immune imbalance of Treg/Th17 in immune thrombocytopenic purpura

BACKGROUND

The imbalance of Treg/Th17 cells is an important pathogenic factor for immune thrombocytopenic purpura (ITP). We previously reported miR-125a-5p targeted CXCL13 and participated in the process of ITP. In the present study, the role of miR-125a-5p in regulating Treg/Th17 ratio and its potential molecular mechanism were investigated.

METHOD

A total of 30 adults with ITP and 30 healthy subjects were included. MEG3 expression in peripheral blood derived CD4+ T cells from ITP patients and healthy subjects were detected by real-time PCR. In vitro experiments, the effects of inhibiting or overexpressing MEG3 on the expression of miR-125a-5p, Foxp3 and ROTγt in CD4+ T cells were investigated.

RESULTS

MEG3 expression was increased in CD4+ T cells of patients with ITP. Dexamethasone decreased MEG3 expression level of CD4+ T cells in vitro. MEG3 directly interacted with miR-125a-5p and MEG3 overexpression inhibited miR-125a-5p expression in CD4+ T cells exposed to dexamethasone. MEG3 down-regulation or miR-125a-5p overexpression promoted Foxp3 expression and inhibited RORγt expression.

CONCLUSION

MEG3 interacted with miR-125a-5p and inhibited its expression, and MEG3/miR-125a-5p contributed to induce immune imbalance of Treg/Th17 in ITP.

Clinical features, outcome and prognostic factors of 87 patients with angioimmunoblastic T cell lymphoma in Taiwan

We retrospectively analyzed 87 patients with angioimmunoblastic T cell lymphoma (AITL) in Taiwan. The median age was 68 (range 18-89) years. Of these patients, 74 % was at an advanced stage. The most common extra-nodal site involved was bone marrow (36 %). Of these patients, 77 % were International Prognostic Index (IPI) >1 and 79 % had a prognostic index for peripheral T-cell lymphoma (PIT) >1. Of 75 patients who received systemic chemotherapy, the complete remission rate was 60 %, the relapse rate was 47 %, and the 2-year progression-free survival rate was 37.4 %. The 2-year overall survival (OS) rate for all patients was 51.9 %. By multivariate analysis, bone marrow involvement (P < 0.001) and ECOG >1 (P = 0.007) were independent adverse factors for OS. A simplified prognostic index efficiently stratified patients into the following three groups: 2-year OS rates 79.8 % (0 factor), 28.3 % (1 factor), and 10.2 % (2 factors) by using bone marrow involvement and ECOG >1 (P < 0.001). In conclusion, AITL patients were older and had poorer prognosis in Taiwan. Bone marrow involvement, EOCG >1, IPI >1 and PIT >1 had adverse impact on OS. The usefulness of this simplified prognostic index needs further validation.

Extranodal Marginal Zone Lymphoma-like Presentations of Angioimmunoblastic T-Cell Lymphoma: A T-Cell Lymphoma Masquerading as a B-Cell Lymphoproliferative Disorder

Angioimmunoblastic T-cell lymphoma (AITL) is the second most common type of peripheral T-cell lymphoma worldwide, and in some countries, it is the most common form. Clinically, AITL usually presents with systemic symptoms, diffuse lymphadenopathy, hepatosplenomegaly, and common laboratory abnormalities such as hypergammaglobulinemia. Rashes are seen in 50%-80% of patients. AITL derives from follicular T-helper cells (TFH), that express germinal center markers and produce hyperactivation of B-cells seen in AITL. Although the histological features of AITL in the skin could be similar to pathological findings present in lymph node biopsies, herein, we present 2 cases of AITL with histological and immunophenotypic features that were somewhat suggestive of extranodal marginal zone lymphoma. Caution is urged to exclude the possibility of a systemic T-cell lymphoma such as AITL in cutaneous and lymph node B-cell proliferations.

An analysis of MYC and EBV in diffuse large B-cell lymphomas associated with angioimmunoblastic T-cell lymphoma and peripheral T-cell lymphoma not otherwise specified

Composite diffuse large B-cell lymphomas (DLBCLs) with peripheral T-cell lymphomas (PTCLs) are rare co-occurrences with poorly understood pathologic features. Herein, we describe 15 distinct cases of DLBCL occurring in association with PTCL, including angioimmunoblastic T-cell lymphoma (AITL; n = 12) and PTCL, not otherwise specified (n = 3). Sheets of large B cells were seen in all cases, with Hodgkin/Reed-Sternberg-like (HRS-L) cells present in 6 cases. When compared to cases of AITL without DLBCL, HRS-L cells were more frequently seen in cases of AITL with DLBCL (P = .02). Epstein-Barr virus (EBV) expression was seen in 10 of 15 cases, and in those with HRS-L cells, EBV expression was detected invariably in at least a subset of the HRS-L cells. MYC gene rearrangements were consistently absent, although 6 of the 10 cases showed MYC overexpression by immunohistochemistry in the neoplastic B cells; a frequency significantly increased compared to other cases of DLBCL not associated with a T-cell lymphoma: 29 of 166 (P = .005). In addition, when MYC was overexpressed in DLBCL, it was also weakly present in the HRS-L cells. The increased and frequent morphologic presence of HRS-L cells in association with this composite lymphoma raises a possible link between their occurrence and DLBCLs in PTCLs; furthermore, the frequent detection of MYC protein expression and EBV infection in these cases suggests a possible role of these pathways in B-cell lymphomagenesis.

Cerebellar EBV-associated diffuse large B cell lymphoma following angioimmunoblastic T cell lymphoma

Epstein-Barr virus (EBV)-associated B cell lymphoproliferative disorders may be seen in patients with angioimmunoblastic T cell lymphoma (AITL). Although both nodal and extranodal sites of involvement have been described, central nervous system involvement by B cell lymphoma following AITL has not previously been documented. We report a first example of such unusual presentation, in which an 80-year-old man developed diffuse large B cell lymphoma (DLBCL) in the cerebellum 4 months after the initial diagnosis of AITL. EBV-encoded RNAs were detected in the DLBCL, suggesting that EBV played a pivotal role in the pathogenesis of high-grade histologic progression of AITL. The patient survived less than 9 months after his initial diagnosis of AITL. We believe that this case expands the spectrum of extranodal manifestation of EBV-positive B cell lymphoma associated with AITL and illustrates the importance of recognition of this association when encountering unusual central nervous system lesions in patients with known AITL.

Epstein-Barr virus-positive T/NK-cell lymphoproliferative disorders

Epstein–Barr virus, a ubiquitous human herpesvirus, can induce both lytic and latent infections that result in a variety of human diseases, including lymphoproliferative disorders. The oncogenic potential of Epstein–Barr virus is related to its ability to infect and transform B lymphocytes into continuously proliferating lymphoblastoid cells. However, Epstein–Barr virus has also been implicated in the development of T/natural killer cell lymphoproliferative diseases. Epstein–Barr virus encodes a series of products that mimic several growth, transcription and anti-apoptotic factors, thus usurping control of pathways that regulate diverse homeostatic cellular functions and the microenvironment. However, the exact mechanism by which Epstein–Barr virus promotes oncogenesis and inflammatory lesion development remains unclear. Epstein–Barr virus-associated T/natural killer cell lymphoproliferative diseases often have overlapping clinical symptoms as well as histologic and immunophenotypic features because both lymphoid cell types derive from a common precursor. Accurate classification of Epstein–Barr virus-associated T/natural killer cell lymphoproliferative diseases is a prerequisite for appropriate clinical management. Currently, the treatment of most T/natural killer cell lymphoproliferative diseases is less than satisfactory. Novel and targeted therapies are strongly required to satisfy clinical demands. This review describes our current knowledge of the genetics, oncogenesis, biology, diagnosis and treatment of Epstein–Barr virus-associated T/natural killer cell lymphoproliferative diseases.

Pathology of T-cell lymphomas: diagnosis and biomarker discovery

T-cell lymphomas are a group of predominantly rare hematologic malignancies that tend to recapitulate different stages of T-cell development, in a similar way that B-cell lymphomas do. As opposed to B-cell lymphomas, the understanding of the biology and the classification of T-cell lymphomas are somewhat rudimentary, and numerous entities are still included as 'provisional categories' in the World Health Classification of hematolopoietic malignancies. A relevant and useful classification of these disorders have been difficult to accomplish because of the rarity nature of them, the relative lack of understanding of the molecular pathogenesis, and their morphological and immunophenotypical complexity. Overall, T-cell lymphomas represent only 15 % of all non-Hodgkin lymphomas. This review is focused on addressing the current status of the categories of mature T-cell leukemias and lymphomas (nodal and extranodal) using an approach that incorporates histopathology, immunophenotype, and molecular understanding of the nature of these disorders, using the same philosophy of the most recent revised WHO classification of hematopoietic malignancies.

Utility of CD279/PD-1 immunohistochemistry in the evaluation of benign and neoplastic T-cell-rich bone marrow infiltrates

OBJECTIVES

CD279 expression is used to help identify angioimmunoblastic T-cell lymphoma (AITL) or other T-cell lymphomas of T-follicular helper (TFH) cell origin; however, its utility in assessing lymphoid infiltrates in the bone marrow (BM) is not well established.

METHODS

Immunohistochemistry for CD279 was performed on normal staging BM and in BM with benign lymphoid aggregates (LAs), AITLs, and other T-cell lymphomas.

RESULTS

Seven of 10 staging BMs demonstrated scattered, usually weakly CD279+ cells. Thirty-four of 38 BMs had scattered weakly/variably intense CD279+ cells within LAs, but only four contained 11% to 25% CD279+ cells. Three of four AITLs were strongly CD279+, but one contained only around 10% CD279+ cells. Eleven of the other 38 T-cell lymphomas were CD279+, including five possible AITLs; four peripheral T-cell lymphomas, not otherwise specified; and two T-cell large granular lymphocytic leukemias.

CONCLUSIONS

Although useful in assessing selected BM lymphoid infiltrates, CD279 expression may be limited in AITLs, is not specific for TFH lymphomas, and can be seen in benign lymphoid infiltrates, although without extensive strong positivity.

Diagnostic accuracy of a defined immunophenotypic and molecular genetic approach for peripheral T/NK-cell lymphomas. A North American PTCL study group project

The diagnosis of peripheral T-cell and NK-cell lymphomas (PTNKCL) is difficult with few standards for required ancillary studies. We evaluated a series of PTNKCLs using a tiered approach to immunohistochemistry and molecular genetic characterization to document diagnostic accuracy and clinical relevance. Seven hematopathologists reviewed 374 cases that included PTNKCL and non-PTNKCL cases to mimic diagnostic practice. Cases received tier 0, 1, and 2 diagnoses by 3 independent pathologists, on the basis of hematoxylin and eosin stains and progressive immunohistochemistry panels. A tier 2b diagnosis was rendered when gene rearrangement data were available, and a final consensus diagnosis was rendered after discussion of each case. Across all 374 cases, consensus agreement was 92.5%. For PTNKCLs, World Health Organization subclassification was possible in 16.5%, 37.1%, 82.8%, and 85.9% of individual reviewer diagnoses at tier 0, 1, 2, and 2b, respectively. Gene rearrangement contributed to a change in diagnosis in 51 of 647 (8%) individual reviews. Following this algorithm may provide prognostic information on the basis of individual marker expression in common PTNKCL types (CD4 in peripheral T-cell lymphoma, not otherwise specified and PD-1 in angioimmunoblastic T-cell lymphoma). This evidence-based approach to the diagnosis of PTNKCL informs practicing pathologists, clinical trial designers, and policy-makers regarding required ancillary studies.

Follicular helper T-cells: expanding roles in T-cell lymphoma and targets for treatment

Follicular helper T-cells (Tfh cells) are a subset of CD4(+) T-cells that are essential for normal production of high affinity antibodies. Tfh cells characteristically produce IL21 and IL4 and show high expression of surface markers CXCR5, ICOS, PDCD1 (PD-1) and the chemokine CXCL13. In this review we will focus on the emerging links between Tfh cells and subtypes of T-cell non-Hodgkin lymphoma: angioimmunoblastic T-cell lymphoma (AITL) and ~20% of peripheral T-cell lymphoma not otherwise specified (PTCL-NOS) have surface marker features of Tfh cells and share a spectrum of genetic abnormalities. The recurrent genetic abnormalities associated with AITL include mutations in epigenetic modifiers such as TET2 and DNMT3A and the motility and adhesion gene, RHOA, is mutated in up to 70% of cases. ~20% of PTCL-NOS demonstrate RHOA mutations and have other characteristics suggesting an origin in Tfh cells. The recognition that specific genetic and surface markers are associated with malignant Tfh cells suggests that the next few years will bring major changes in diagnostic and treatment possibilities. For example, antibodies against IL21, PDCD1 and ICOS are already in clinical trials for autoimmune disease or other malignancies and antibodies against CXCL13 are in pre-clinical development.

The microenvironment in T-cell lymphomas: emerging themes

Peripheral T-cell lymphomas (PTCLs) are heterogeneous and uncommon malignancies characterized by an aggressive clinical course and a mostly poor outcome with current treatment strategies. Despite novel insights into their pathobiology provided by recent genome-wide molecular studies, several entities remain poorly characterized. In addition to the neoplastic cell population, PTCLs have a microenvironment component, composed of non-tumor cells and stroma, which is quantitatively and qualitatively variable, and which may have an effect on their pathological and clinical features. The best example is provided by angioimmunoblastic T-cell lymphoma (AITL), a designation reflecting the typical vascularization and reactive immunoblastic content of the tumor tissues. In this disease, a complex network of interactions between the lymphoma cells and the microenvironment exists, presumably mediated by the neoplastic T cells with follicular helper T-cell properties. A better understanding of the crosstalk between neoplastic T or NK cells and their microenvironment may have important implications for guiding the development of novel therapies.

Nodular lymphocyte predominant hodgkin lymphoma and T cell/histiocyte rich large B cell lymphoma--endpoints of a spectrum of one disease?

In contrast to the commonly indolent clinical behavior of nodular lymphocyte predominant Hodgkin lymphoma (NLPHL), T cell/histiocyte rich large B cell lymphoma (THRLBCL) is frequently diagnosed in advanced clinical stages and has a poor prognosis. Besides the different clinical presentations of these lymphoma entities, there are variants of NLPHL with considerable histopathologic overlap compared to THRLBCL. Especially THRLBCL-like NLPHL, a diffuse form of NLPHL, often presents a histopathologic pattern similar to THRLBCL, suggesting a close relationship between both lymphoma entities. To corroborate this hypothesis, we performed gene expression profiling of microdissected tumor cells of NLPHL, THRLBCL-like NLPHL and THRLBCL. In unsupervised analyses, the lymphomas did not cluster according to their entity. Moreover, even in supervised analyses, very few consistently differentially expressed transcripts were found, and for these genes the extent of differential expression was only moderate. Hence, there are no clear and consistent differences in the gene expression of the tumor cells of NLPHL, THRLBCL-like NLPHL and THRLBCL. Based on the gene expression studies, we identified BAT3/BAG6, HIGD1A, and FAT10/UBD as immunohistochemical markers expressed in the tumor cells of all three lymphomas. Characterization of the tumor microenvironment for infiltrating T cells and histiocytes revealed significant differences in the cellular composition between typical NLPHL and THRLBCL cases. However, THRLBCL-like NLPHL presented a histopathologic pattern more related to THRLBCL than NLPHL. In conclusion, NLPHL and THRLBCL may represent a spectrum of the same disease. The different clinical behavior of these lymphomas may be strongly influenced by differences in the lymphoma microenvironment, possibly related to the immune status of the patient at the timepoint of diagnosis.

Pathobiology of T-cell and NK-cell lymphomas

T-cell and NK-cell lymphomas are uncommon lymphomas with an aggressive clinical course. The causes and precise cellular origins of most T-cell lymphomas are still not well defined. The WHO classification utilizes morphologic and immunophenotypic features in conjunction with clinical aspects and in some instances genetics to delineate a prognostically and therapeutically meaningful categorization. The anatomic localization of neoplastic T-cells and NK-cells parallels in part their proposed normal cellular counterparts and functions. T-cells of the adaptive immune system are mainly based in lymph nodes and peripheral blood, whereas lymphomas derived from T-cells and NK-cells of the innate immune system are mainly extranodal. This approach allows for better understanding of some of the manifestations of the T-cell and NK-cell lymphomas, including their cellular distribution, some aspects of morphology and even associated clinical findings.

Follicular center helper T-cell (TFH) marker positive mycosis fungoides/Sezary syndrome

We identified 11 patients with CD10(+) cutaneous T-cell lymphoma by flow cytometry. All cases were CD4(+) and CD8(-). Three patients had extensive lymphadenopathy, systemic symptoms and an aggressive clinical course consistent with angioimmunoblastic T-cell lymphoma or peripheral T-cell lymphoma. However, 8 of the 11 patients had a prolonged disease course with gross morphology, histology and tumor cell phenotype indistinguishable from mycosis fungoides or Sezary syndrome. Immunohistochemical studies confirmed CD10 expression in seven of the eight cases and revealed the lymphoma cells were Bcl-6(+), PD-1(+), and EBV(-). Two had significant expression of CXCL-13(+). The findings indicate that lymphoma cells from mycosis fungoides or Sezary syndrome may express follicular center helper T-cell markers CD10, Bcl-6, and PD-1 and occasionally CXCL-13. The expression of these markers in some cases of mycosis fungoides/Sezary syndrome suggests follicular center helper T-cell differentiation and may lead to confusion in distinguishing mycosis fungoides/Sezary syndrome from other follicular center helper T-cell marker positive T-cell lymphomas with cutaneous manifestations.

Follicular T-cell lymphoma: a member of an emerging family of follicular helper T-cell derived T-cell lymphomas

Unlike B-cell lymphomas, where knowledge of normal B-cell origin and differentiation has greatly contributed to their classification, the current classification of peripheral T-cell lymphomas is limited by a lack of understanding of their cellular origin. In the current World Health Organization classification of lymphomas, follicular T-cell lymphoma was formally recognized as a morphologic variant of peripheral T-cell lymphoma, not otherwise specified. There is growing evidence, however, that follicular T-cell lymphoma may be a unique clinicopathologic entity based on its morphologic features and derivation from follicular helper T-cells. In addition, there are abundant recent data supporting the concept that follicular helper T-cells can give rise to other types of T-cell lymphoma, including angioimmunoblastic T-cell lymphoma, primary cutaneous CD4+ small/medium T-cell lymphoma, and a subset of neoplasms, in addition to follicular T-cell lymphoma, currently classified as peripheral T-cell lymphoma, not otherwise specified. In this review, we focus primarily on the clinicopathologic, immunophenotypic, and molecular features of follicular T-cell lymphoma and discuss its potential relationship with other types of T-cell lymphoma thought to be derived from follicular helper T-cells.

Atypical angioimmunoblastic T-cell lymphomas masquerading as systemic polyclonal B-immunoblastic proliferation

Angioimmunoblastic T cell lymphoma (AITL) is a relatively rare peripheral T cell lymphoma derived from follicular T helper cells. AITL has a varied presentation, both clinically and morphologically. AITL can pose a diagnostic challenge as it may be difficult to identify and characterize the neoplastic cells among the polymorphous infiltrates composed of polyclonal B immunoblasts and plasma cells. In AITL, the reactive B cell and plasma cell proliferation is secondary to dysregulated secretion of cytokines such as interleukin-6 by the neoplastic follicular T helper cells. SPBIP is a condition of unknown etiopathogenesis characterized by systemic involvement by polyclonal B immunoblasts and plasma cells. We report two cases of AITL, which are presented with atypical findings making it difficult to diagnose. The cases had features similar to SPBIP. Our cases highlight the importance of screening cases of polyclonal plasmacytosis and SPBIP like cases for underlying AITL.

Successful treatment of chemotherapy-refractory angioimmunoblastic T cell lymphoma with cyclosporin A

Angioimmunoblastic T cell lymphoma (AITL) is a rare subtype of T cell non-Hodgkin lymphoma. The standard therapeutic strategy for AITL has not yet been established, and its prognosis remains poor. This report concerns the effect of cyclosporin A (CsA) on chemotherapy-refractory AITL. A 68-year-old female with AITL with systemic symptoms, such as high fever, skin rash and generalized lymphadenopathy, was initially treated with conventional cytotoxic chemotherapies using alkylators, anthracyclines and corticosteroids, which failed to induce remission. However, CsA (4 mg/kg/day) plus dexamethasone treatment resulted in a dramatic regression of the tumors and amelioration of systemic symptoms and induced complete remission (CR) within 2 weeks. Currently, the patient's CR has continued for more than 18 months with CsA maintenance therapy. Our experience and previously reported findings suggest that CsA may constitute an alternative treatment option for AITL, even though the use of conventional cytotoxic chemotherapy continues to be the first-line therapy on an empirical basis.

Angioimmunoblastic T-cell lymphoma: the effect of initial treatment and microvascular density in 31 patients

The objectives of this study are to explore the clinical features and treatment outcomes and to investigate the correlation between microvessel density (MVD) and survival in patients with angioimmunoblastic T-cell lymphoma (AITL). We retrospectively analyzed clinical and follow-up data of 31 patients treated in two hospitals during 1995-2009 histologically proven AITL. We also assessed MVD in the lump of 31 previously untreated patients using α-CD34 immunohistochemical staining. The median age of the 31 patients was 48 years, eighty percent of the patients were in an advanced stage. 67.7% of them had B symptoms, with the follow-up of 2-13 years, the 5-year overall survival rate was 25.8%. The response rates (RR) of CHOP group and COP (cyclophosphamide, vincristine and prednisolone) group are 76.5 and 75%, respectively, which is no significant difference (P=0.894). RR did not differ whether chemotherapy regimens contained anthracycline or not. The 3-year PFS rate for patients who received COP and CHOP regimen was 25.4 and 35.3% (P=0.562), while 5-year OS rates were 25.0 and 29.4%, respectively (P=0.667). The median PFS for patients with high MVD and low MVD were 15.1 and 30.0 months (P=0.048), while the median OS were 20 and 45 months, respectively (P=0.038). Patients who were sensitive to initial chemotherapy COP regimen have the similar therapeutic effect to CHOP regimen. Patients with high MVD measured in the microenvironment had worse PFS and OS than AITL patients with low expression.

Peripheral T cell lymphomas with follicular T helper phenotype: a new basket or a distinct entity? Revising Karl Lennert’s personal archive

AIMS

To revise 25 cases selected from Karl Lennert's personal archive (21) and Bologna and Frankfurt Registries (four) because of cytological similarities.

METHODS AND RESULTS

All cases were provided with paraffin blocks and studied by immunohistochemistry and molecular techniques. While phenotyping was very informative, among molecular studies only EBER in situ-hybridization (ISH) was successful. Twenty-two cases were concluded as peripheral T cell lymphomas (PTCL). Of these, six were reclassified as angioimmunoblastic T cell lymphoma (AITL), 13 as PTCL, not otherwise specified (NOS), including four follicular variants and one tumour with T-zone pattern, and three as borderline tumours between AITL and PTCL/NOS. All these cases consisted homogeneously of small/medium-sized elements with mild nuclear atypia and an evident rim of clear/pale cytoplasm. On immunohistochemistry, they regularly expressed three to six follicular helper T cell (FTH)-associated markers. EBER-ISH revealed scattered EBV-infected B cells in all tumours except those with 'follicular' growth pattern. The content of follicular dendritic cells and high-endothelial venules varied significantly depending on the histotype.

CONCLUSIONS

This study shows that: (i) historical material can be still employed usefully, and (ii) the FTH-phenotype corresponds to a broad spectrum of PTCLs that might form a new category to be validated in future molecular and clinicopathological analyses.