Angioimmunoblastic T-cell lymphoma involving the nasopharynx: An easily misdiagnosed disease with atypical histopathological features.

OBJECTIVES: To explore the clinicopathologic features, treatment, and survival outcomes of angioimmunoblastic T-cell lymphoma (AITL) involving the nasopharynx. METHODS: We retrospectively analyzed 73 cases of AITL. Among them, 64 cases with complete pre-treatment 18F-FDG positron emission tomography/computed tomography (PET/CT) images were integrated into the analysis of clinical characteristics and PET/CT findings of AITL involving the nasopharynx; 14 cases with both biopsies from lymph node and nasopharynx were included in the comparison of pathological characteristics of AITL in the two areas. Forty-six of the 73 patients who received first-line systemic treatment at our institute were included in the treatment efficacy and survival analyses. RESULTS: Nasopharyngeal involvement was seen in 44/64 (68.8%) patients. Histologically, lymph node and nasopharyngeal biopsies in 14 patients both showed small to medium-sized tumor cells, complex inflammatory infiltration, and Reed-Sternberg-like cells or B immunoblasts. However, tumor cells with clear cytoplasm, significant high endothelial venule (HEV) hyperplasia, and perivascular infiltration were observed in 5/14, 3/14, and 2/14 nasopharyngeal biopsies, respectively, but in all fourteen lymph node biopsies (P < 0.05). Immunophenotypic profiles and gene rearrangements were highly concordant. Treatment efficacy and survival were similar between patients with nasopharyngeal involvement and those without (P > 0.05), indicating nasopharyngeal involvement is not a prognostic factor for AITL patients. CONCLUSIONS: Nasopharyngeal involvement is common in AITL but can be easily misdiagnosed because of its atypical pathologic pattern, especially when a lymph node biopsy is unavailable. However, the patient's clinical presentation, PET/CT manifestations, the typical immunophenotype, and gene rearrangements help the diagnosis.

Clonal haematopoiesis: A common progenitor for cytotoxic peripheral T-cell lymphoma and angioimmunoblastic T-cell lymphoma.

Recent studies have shown that follicular helper T-cell lymphoma of angioimmunoblastic type (AITL), the most common nodal peripheral T-cell lymphoma (PTCL), frequently arises in a background of clonal haematopoiesis (CH), a preneoplastic condition affecting up to 40% of elderly individuals. Data on a potential CH association are limited for other PTCL. We report a unique patient who sequentially developed both cytotoxic PTCL, not otherwise specified and AITL with distinct T-cell receptor rearrangements but shared somatic mutations originating from the same CH clone, thus providing convincing evidence that CH can give rise to T-cell neoplasms of different lineage.

Inhibition of choline metabolism in an angioimmunoblastic T-cell lymphoma preclinical model reveals a new metabolic vulnerability as possible target for treatment.

BACKGROUND: Angioimmunoblastic T-cell lymphoma (AITL) is a malignancy with very poor survival outcome, in urgent need of more specific therapeutic strategies. The drivers of malignancy in this disease are CD4+ follicular helper T cells (Tfh). The metabolism of these malignant Tfh cells was not yet elucidated. Therefore, we decided to identify their metabolic requirements with the objective to propose a novel therapeutic option. METHODS: To reveal the prominent metabolic pathways used by the AITL lymphoma cells, we relied on metabolomic and proteomic analysis of murine AITL (mAITL) T cells isolated from our established mAITL model. We confirmed these results using AITL patient and healthy T cell expression data. RESULTS: Strikingly, the mAITL Tfh cells were highly dependent on the second branch of the Kennedy pathway, the choline lipid pathway, responsible for the production of the major membrane constituent phosphatidylcholine. Moreover, gene expression data from Tfh cells isolated from AITL patient tumors, confirmed the upregulation of the choline lipid pathway. Several enzymes involved in this pathway such as choline kinase, catalyzing the first step in the phosphatidylcholine pathway, are upregulated in multiple tumors other than AITL. Here we showed that treatment of our mAITL preclinical mouse model with a fatty acid oxydation inhibitor, significantly increased their survival and even reverted the exhausted CD8 T cells in the tumor into potent cytotoxic anti-tumor cells. Specific inhibition of Chokα confirmed the importance of the phosphatidylcholine production pathway in neoplastic CD4 + T cells, nearly eradicating mAITL Tfh cells from the tumors. Finally, the same inhibitor induced in human AITL lymphoma biopsies cell death of the majority of the hAITL PD-1high neoplastic cells. CONCLUSION: Our results suggest that interfering with choline metabolism in AITL reveals a specific metabolic vulnerability and might represent a new therapeutic strategy for these patients.

Angioimmunoblastic T-cell lymphoma and Kaposi sarcoma: A fortuitous collision?

AIMS: Follicular helper T-cell (TFH) lymphoma of the angioimmunoblastic-type (AITL), one of the most prevalent T-cell lymphomas, typically encompasses proliferation of high endothelial venules and Epstein-Barr virus-positive immunoblasts, but neither infection with HHV8 nor association with Kaposi's sarcoma (KS) have been described. The aims of this study are to characterise the association between AITL and HHV8 infection or KS. METHODS AND RESULTS: Three male patients aged 49-76 years, HIV-negative, with concurrent nodal involvement by AITL and KS, were identified from our files and carefully studied. Two patients originated from countries where endemic KS occurs, including one with cutaneous KS. The lymphomas featured abundant vessels, expanded follicular dendritic cells and neoplastic TFH cells [PD1+ (three of three), ICOS+ (three of three), CXCL13+ (three of three), CD10+ (two of three), BCL6 (two of three)] but lacked EBV+ immunoblasts. The foci of KS consisted of subcapsular proliferations of ERG+, CD31+ and/or CD34+ , HHV8+ spindle cells. High-throughput sequencing showed AITL-associated mutations in TET2 (three of three), RHOA (G17V) (three of three) and IDH2 (R172) (two of three), which were absent in the microdissected KS component in two cases. Relapses in two patients consisted of AITL, without evidence of KS. No evidence of HHV8 infection was found in a control group of 23 AITL cases. CONCLUSION: Concurrent nodal involvement by AITL and KS is rare and identification of both neoplastic components may pose diagnostic challenges. The question of whether the association between AITL and KS may be fortuitous or could reflect the underlying immune dysfunction in AITL remains open.

Angioimmunoblastic T-cell lymphoma: Novel recurrent mutations and prognostic biomarkers by cell-free DNA profiling.

Molecular and clinical stratification of patients with angioimmunoblastic T-cell lymphoma (AITL) is unsatisfactory, which hinders the development of personalized therapies. This study aimed to identify molecular biomarkers for AITL based on peripheral cell-free DNA (cfDNA) that could be used to predict prognosis and guide treatment non-invasively. A customized panel containing 46 genes was used to study pretreatment cfDNA and paired tumour tissues in 64 Chinese AITL patients from three clinical centres, and gene mutations in cfDNA and tumour tissue were assessed for concordance (34 paired samples). Then, the association of gene mutations and prognosis was analysed, and a functional enrichment analysis was performed. The sequencing results showed good consistency between cfDNA samples and paired tissue samples. KDM5A, STAT1, FANCM, ERBB4, PIK3R5 and NSD1 were identified as novel recurrent mutations. Mutations in FANCM or combinations of RHOA, KDM5A and FAT1 were associated with poor prognosis. Additionally, functional analysis revealed that RHOAG17 might serve as a predictive biomarker of PD-1 blockade respondence. Our findings confirmed the role of cfDNA as a liquid biopsy in AITL, and revealed novel molecular determinants that can stratify patients and guide treatment options.

[Analysis of clinicopathological and molecular abnormalities of angioimmunoblastic T-cell lymphoma].

OBJECTIVE: To analyze the clinicopathological features, molecular changes and prognostic factors in angioimmunoblastic T-cell lymphoma (AITL). METHODS: Sixty-one cases AITL diagnosed by Department of Pathology of Peking University Cancer Hospital were collected with their clinical data. Morphologically, they were classified as typeⅠ[lymphoid tissue reactive hyperplasia (LRH) like]; typeⅡ[marginal zone lymphoma(MZL)like] and type Ⅲ [peripheral T-cell lymphoma, not specified (PTCL-NOS) like]. Immunohistochemical staining was used to evaluate the presence of follicular helper T-cell (TFH) phenotype, proliferation of extra germinal center (GC) follicular dendritic cells (FDCs), presence of Hodgkin and Reed-Sternberg (HRS)-like cells and large B transformation. The density of Epstein-Barr virus (EBV) + cells was counted with slides stained by Epstein-Barr virus encoded RNA (EBER) in situ hybridization on high power field (HPF). T-cell receptor / immunoglobulin gene (TCR/IG) clonality and targeted exome sequencing (TES) test were performed when necessary. SPSS 22.0 software was used for statistical analysis. RESULTS: Morphological subtype (%): 11.4% (7/61) cases were classified as type Ⅰ; 50.8% (31/61) as type Ⅱ; 37.8% (23/61) as type Ⅲ. 83.6% (51/61) cases showed classical TFH immunophenotype. With variable extra-GC FDC meshwork proliferation (median 20.0%); 23.0% (14/61) had HRS-like cells; 11.5% (7/61) with large B transformation. 42.6% (26/61) of cases with high counts of EBV. 57.9% (11/19) TCR+/IG-, 26.3% (5/19) TCR+/IG+, 10.5% (2/19) were TCR－/IG－, and 5.3% (1/19) TCR－/IG+. Mutation frequencies by TES were 66.7% (20/30) for RHOA, 23.3% (7/30) for IDH2 mutation, 80.0% (24/30) for TET2 mutation, and 33.3% (10/30) DNMT3A mutation. Integrated analysis divided into four groups: (1) IDH2 and RHOA co-mutation group (7 cases): 6 cases were type Ⅱ, 1 case was type Ⅲ; all with typical TFH phenotype; HRS-like cells and large B transformation were not found; (2) RHOA single mutation group (13 cases): 1 case was type Ⅰ, 6 cases were type Ⅱ, 6 cases were type Ⅲ; 5 cases without typical TFH phenotype; 6 cases had HRS-like cells, and 2 cases with large B transformation. Atypically, 1 case showed TCR－/IG－, 1 case with TCR－/IG+, and 1 case with TCR+/IG+; (3) TET2 and/or DNMT3A mutation alone group (7 cases): 3 cases were type Ⅱ, 4 cases were type Ⅲ, all cases were found with typical TFH phenotype; 2 cases had HRS-like cells, 2 cases with large B transformation, and atypically; (4) non-mutation group (3 cases), all were type Ⅱ, with typical TFH phenotype, with significant extra-GC FDC proliferation, without HRS-like cells and large B transformation. Atypically, 1 case was TCR－/IG－. Univariate analysis confirmed that higher density of EBV positive cell was independent adverse prognostic factors for both overall survival (OS) and progression free survival(PFS), (P=0.017 and P=0.046). CONCLUSION: Pathological diagnoses of ALTL cases with HRS-like cells, large B transformation or type Ⅰ are difficult. Although TCR/IG gene rearrangement test is helpful but still with limitation. TES involving RHOA, IDH2, TET2, DNMT3A can robustly assist in the differential diagnosis of those difficult cases. Higher density of EBV positive cells counts in tumor tissue might be an indicator for poor survival.

Peripheral T-cell lymphoma with a T follicular-helper phenotype: A different entity? Results of the Spanish Real-T study.

Nodal peripheral T-cell lymphoma (PTCL) with a T follicular helper phenotype (PTCL-TFH) is a new type of PTCL. We aimed to define its clinical characteristics and prognosis compared to PTCL not otherwise specified (PTCL-NOS) and angioimmunoblastic T-cell lymphoma (AITL). This retrospective observational study included 175 patients diagnosed with PTCL between 2008 and 2013 in 13 Spanish sites. Patient diagnosis was centrally reviewed, and patients were reclassified according to the World Health Organization (WHO) 2016 criteria: 21 patients as PTCL-NOS, 55 as AITL and 23 as PTCL-TFH. Median follow-up was 56.07 months (95% CI 38.7-73.4). Progression-free survival (PFS) and overall survival (OS) were significantly higher in patients with PTCL-TFH than in those with PTCL-NOS and AITL (PFS, 24.6 months vs. 4.6 and 7.8 months, respectively, p = 0.002; OS, 52.6 months vs. 10.0 and 19.3 months, respectively, p < 0.001). Histological diagnosis maintained an independent influence on both PFS (hazard ratio [HR] 4.1 vs. PTCL-NOS, p = 0.008; HR 2.6 vs. AITL, p = 0.047) and OS (HR 5.7 vs. PTCL-NOS, p = 0.004; HR 2.6 vs. AITL, p = 0.096), regardless of the International Prognostic Index. These results suggest that PTCL-TFH could have more favourable features and prognosis than the other PTCL subtypes, although larger series are needed to corroborate these findings.

DNMT3AR882H accelerates angioimmunoblastic T-cell lymphoma in mice.

DNA methylation-related genes, including TET2, IDH2, and DNMT3A are highly frequently mutated in angioimmunoblastic T-cell lymphoma (AITL), an aggressive malignancy of T follicular helper (Tfh) cells associated with aberrant immune features. It has been shown that TET2 loss cooperates with RHOAG17V to promote AITL in mice but the functional role of DNMT3A mutations in AITL remains unclear. Here, we report that DNMT3AR882H, the most common mutation of DNMT3A in AITL, accelerates the development of Tet2-/-; RHOAG17V AITL in mice, indicated by the expansion of malignant Tfh cells and aberrant B cells, skin rash, and significantly shortened disease-free survival. To understand the underlying cellular and molecular mechanisms, we performed single-cell transcriptome analyses of lymph nodes of mice transplanted with Tet2-/-, Tet2-/-; RHOAG17V or DNMT3AR882H; Tet2-/-; RHOAG17V hematopoietic stem and progenitor cells. These single-cell landscapes reveal that DNMT3A mutation further activates Tfh cells and leads to rapid and terminal differentiation of B cells, probably through enhancing the interacting PD1/PD-L1, ICOS/ICOSL, CD28/CD86, and ICAM1/ITGAL pairs. Our study establishes the functional roles of DNMT3A mutation in AITL and sheds light on the molecular mechanisms of this disease.

Benefit of prednisolone alone in nodal peripheral T-cell lymphoma with T follicular helper phenotype.

A 71-year-old Japanese man presented with severe thrombocytopenia. A whole-body CT at presentation showed small cervical, axillary, and para-aortic lymphadenopathy, leading to suspicion of immune thrombocytopenia due to lymphoma. Biopsy was difficult to perform because of severe thrombocytopenia. Thus, he received prednisolone (PSL) therapy and his platelet count gradually recovered. Two and a half years after PSL therapy initiation, his cervical lymphadenopathy slightly progressed without other clinical symptoms. Hence, a biopsy from the left cervical lymph node was performed, and he was diagnosed with nodal peripheral T-cell lymphoma (PTCL) with T follicular helper (TFH) phenotype. Due to various complications, we continued treatment with prednisolone alone after the diagnosis of lymphoma; however, there was no further increase in lymph node enlargement and no other lymphoma-related symptoms for one and a half years after diagnosis. Although immunosuppressive therapy has been reported to produce a response in some patients with angioimmunoblastic T-cell lymphoma, our experience suggests that a similar subset may exist in patients with nodal PTCL with TFH phenotype, which has the same cellular origin. Immunosuppressive therapies may constitute an alternative treatment option even in the era of novel molecular-targeted therapies, especially for elderly patients who are ineligible for chemotherapy.

Follicular Helper T-Cell-derived Nodal Lymphomas: Study of Histomorphologic, Immunophenotypic, Clinical, and RHOA G17V Mutational Profile.

The study was designed to review the demographic, clinical, and pathologic characteristics of follicular helper T cells (TFH)-derived nodal PTCL in India including angioimmunoblastic T-cell lymphoma (AITL), peripheral T-cell lymphoma (PTCL) with follicular helper T cell phenotype (P-TFH), and follicular T-cell lymphoma with additional immunohistochemistry (IHC) and RHOAG17V mutational analysis, as well as their impact on survival. This retrospective study included 88 cases of PTCL that were reclassified using IHC for TFH markers (PD1, ICOS, BCL6, and CD10) and dendritic-meshwork markers (CD21, CD23). Cases of TFH cell origin were evaluated for RHOAG17V mutation using Sanger sequencing and amplification-refractory mutation system-polymerase chain reaction (PCR) (validated using cloning and quantitative PCR) with detailed clinicopathologic correlation. Extensive re-evaluation with added IHC panel resulted in a total of 19 cases being reclassified, and the final subtypes were AITL (37 cases, 42%), PTCL-not otherwise specified (44, 50%), P-TFH (6, 7%), and follicular T-cell lymphoma (1, 1%). The presence of at least 2 TFH markers (>20% immunopositivity) determined the TFH origin. AITL patients tended to be male and showed increased presence of B-symptoms and hepatosplenomegaly. Histomorphology revealed that 92% of AITL cases had pattern 3 involvement. Sanger sequencing with conventional PCR did not yield any mutation, while RHOAG17V was detected by amplification-refractory mutation system-PCR in AITL (51%, P =0.027) and P-TFH (17%), which was validated with cloning followed by sequencing. Cases of RHOAG17V-mutant AITL had a worse Eastern Cooperative Oncology Group performance status initially but fared better in terms of overall outcome ( P =0.029). Although not specific for AITL, RHOAG17V mutation shows an association with diagnosis and requires sensitive methods for detection due to low-tumor burden. The mutant status of AITL could have prognostic implications and translational relevance.

IDH2 and TET2 mutations synergize to modulate T Follicular Helper cell functional interaction with the AITL microenvironment.

Angioimmunoblastic T cell lymphoma (AITL) is a peripheral T cell lymphoma that originates from T follicular helper (Tfh) cells and exhibits a prominent tumor microenvironment (TME). IDH2 and TET2 mutations co-occur frequently in AITL, but their contribution to tumorigenesis is poorly understood. We developed an AITL mouse model that is driven by Idh2 and Tet2 mutations. Malignant Tfh cells display aberrant transcriptomic and epigenetic programs that impair TCR signaling. Neoplastic Tfh cells bearing combined Idh2 and Tet2 mutations show altered cross-talk with germinal center B cells that promotes B cell clonal expansion while decreasing Fas-FasL interaction and reducing B cell apoptosis. The plasma cell count and angiogenesis are also increased in the Idh2-mutated tumors, implying a major relationship between Idh2 mutation and the characteristic AITL TME. Our mouse model recapitulates several features of human IDH2-mutated AITL and provides a rationale for exploring therapeutic targeting of Tfh-TME cross-talk for AITL patients.

Flow Cytometry Analysis Reveals a Wide Cytologic and Immunophenotypic Spectrum of Peripheral B Lymphocytes in Angioimmunoblastic T-Cell Lymphoma.

INTRODUCTION: Angioimmunoblastic T-cell lymphoma (AITL) is an aggressive T-cell lymphoma commonly associated with B-cell dysregulation. Correlations involving B-cell dysregulation and clinicopathological features remain unclear. METHODS: We prospectively collected blood samples from 11 AITL patients and 17 healthy controls. The percentages of B-cell subpopulations and lymphocytes with IL-21 production were assessed using flow cytometry. Peripheral blood lymphocyte morphology was evaluated microscopically. RESULTS: Six of 11 (54.5%) patients presented with polyclonal hypergammaglobulinemia. Three of 11 (27.3%) tumor biopsies showed monoclonal immunoglobulin gene rearrangement. The patients exhibited significantly lower levels of naive (p < 0.001) and class-switched (p < 0.001) B cells than controls. The percentages of IgD-CD27- B cells (p = 0.007) and antibody-secreting cells (ASCs) (p = 0.001) were increased. Blood smears revealed atypical lymphocytes and immature plasma cells with morphological diversity. In comparison to normal controls, IL-21 production significantly increased in CD4+ (p < 0.001) and CD8+ (p = 0.020) T cells. B-cell clonality, RHOA G17V mutation, and the presence of sheets of clear cells and immature/mature plasma cells in lymph nodes were significantly associated with percentages of class-switched B cells and ASCs. The patients with circulating EBV DNA had a lower percentage of naive B cells (p = 0.009). CONCLUSIONS: Our results demonstrated a wide spectrum of peripheral B-cell morphologies and immunophenotypes of peripheral B cells in AITL. These findings correspond to dysregulated B-cell immunity and heterogeneous clinicopathological features.

Cardiac Tamponade as a Recurrence of Angioimmunoblastic T-Cell Lymphoma with the Detection of a p.Gly17Val RHOA Mutation in the Pericardial Effusion.

Angioimmunoblastic T-cell lymphoma (AITL) is an intractable type of T-cell lymphoma. We and others have identified that the p.Gly17Val RHOA mutation is specifically identified in AITL. We herein report a patient whose condition deteriorated, resulting from massive pericardial effusion one month after undergoing autologous transplantation for AITL. He was diagnosed with cardiac tamponade caused by AITL recurrence in the presence of the p.Gly17Val RHOA mutation as well as T-lineage cells with an aberrant immune-phenotype in the pericardial effusion. This case suggests that a precision medicine approach by detecting the presence of a p.Gly17Val RHOA mutation is useful for the management of AITL.

Spatial Transcriptomics Analysis Reveals that CCL17 and CCL22 are Robust Indicators of a Suppressive Immune Environment in Angioimmunoblastic T Cell Lymphoma (AITL).

BACKGROUND: T cell lymphoma is a complex and highly aggressive clinicopathological entity with a poor outcome. The angioimmunoblastic T-cell lymphoma (AITL) tumor immune microenvironment is poorly investigated. METHODS: Here, to the best of our knowledge, spatial transcriptomics was applied for the first time to study AITL. RESULTS: Using this method, we observed that AITL was surrounded by cells bearing immune-suppressive markers. CCL17 and CCL22, the dominant ligands for CCR4, were up-regulated, while the expression of natural killer (NK) cell and CD8+ cytotoxic T lymphocyte (CTL) markers decreased. Colocalization of Treg cells with the CD4+ TFH-GC region was also deduced from the bioinformatic analysis. The results obtained with spatial transcriptomics confirm that AITL has a suppressive immune environment. Chemotherapy based on the CHOP regimen (cyclophosphamide, doxorubicin, vincristine plus prednisone) induced complete remission (CR) in this AITL patient. However, the duration of remission (DoR) remains a concern. CONCLUSIONS: This study demonstrates that AITL has an immune suppressive environment and suggests that anti-CCR4 therapy could be a promising treatment for this lethal disease.

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.

TET-2 mutations predict poor outcomes and are associated with unfavorable clinical-biological features in PTCL, not otherwise specified and angioimmunoblastic T-cell lymphoma in Brazilian patients.

INTRODUCTION: Nodal peripheral T-cell lymphomas [nPTCL] constitute a heterogeneous group of rare malignancies with aggressive biological behavior and poor prognosis. Epigenetic phenomena involving genes that control DNA-methylation and histone deacetylation play a central role in their pathogenesis. However, the mutational landscape involving epigenetic regulators has never been reported in Latin American patients and their prognostic impact remains controversial. PATIENTS AND METHODS: From 2000 to 2019, 59-Brazilian patients with nPTCL were eligible for screening mutations in the IDH-1, IDH-2, RHOA, TET-2 and DNMT3A genes by Sanger sequencing at Formalin-Fixed Paraffin-Embedded samples [FFPE] of diagnosis. We reported the frequency, distribution and potential prognosis of these mutations. RESULTS: With a median follow-up of 3.70 years, estimate 2-year OS and PFS were 57.1% and 49.2%, respectively. Mutations in the IDH-1 gene were not found, mutations in the IDH-2 occurred in 3.4% (2/59), RHOA in 23.7% (14/59), TET-2 in 50.8% (30/59) and DNMT3A in 62.7% (37/59). RHOA gene mutations were more frequent in PTCL, NOS and AITL (p= 0.06). Almost half of the patients had more than one mutation in concomitance, particularly RHOA-mut and TET-2-mut. Mutations in RHOA (p= 0.030) and TET-2 (p= 0.046) were associated with high-tumor burden. In the non-ALCL subgroup (PTCL, NOS and AITL) TET-2 mutations were associated with decreased 2-year PFS [HR: 2.22, p= 0.048]. Likewise with lower overall response rate [ORR] (p= 0.048) and unfavorable clinical features, as bulky disease (p= 0.012), ECOG ⩾ 2 (p= 0.032), B-symptoms (p= 0.012), ⩾ 2 extranodal sites compromised (p= 0.022) and high-risk Prognostic Index for T-cell lymphoma (p= 0.005). CONCLUSION: Mutations in RHOA, TET-2 and DNMT3A were frequent in Brazilian patients with nPTCL. TET-2 mutations were associated with lower ORR for CHOP-like chemotherapy, decreased PFS and unfavorable clinical-biological characteristics in non-ALCL (PTCL, NOS and AITL). Further studies using a larger cohort may validate our findings.

Angioimmunoblastic T-Cell Lymphoma with Exuberant CD30-Positive Follicular Dendritic Cell Proliferation in a SARS-CoV-2 Patient: The Role of Mutational Analysis to Exclude an Associated Follicular Dendritic Cell Sarcoma.

Follicular dendritic cell (FDC) proliferation in angioimmunoblastic T-cell lymphoma (AITL) is still not well defined, challenging the accurate differential diagnosis between the AITL with expanded follicular dendritic cell meshwork and the combined AITL and follicular dendritic cell sarcoma (FDCS). Herein, we reported the case of a 58-year-old male with coexisting SARS-CoV-2 infection and AITL with an exuberant CD30-positive FDC proliferation, in which genetic analysis identified mutations of genes commonly involved in AITL but not in FDC sarcoma (i.e., RHOA, TET2, DNMT3A, and IDH2), thus supporting the reactive nature of the CD30-positive FDC expansion.

Clonal germinal center B cells function as a niche for T-cell lymphoma.

Angioimmunoblastic T-cell lymphoma (AITL) is proposed to be initiated by age-related clonal hematopoiesis (ACH) with TET2 mutations, whereas the G17V RHOA mutation in immature cells with TET2 mutations promotes the development of T follicular helper (TFH)-like tumor cells. Here, we investigated the mechanism by which TET2-mutant immune cells enable AITL development using mouse models and human samples. Among the 2 mouse models, mice lacking Tet2 in all the blood cells (Mx-Cre × Tet2flox/flox × G17V RHOA transgenic mice) spontaneously developed AITL for approximately up to a year, while mice lacking Tet2 only in the T cells (Cd4-Cre × Tet2flox/flox × G17V RHOA transgenic mice) did not. Therefore, Tet2-deficient immune cells function as a niche for AITL development. Single-cell RNA-sequencing (scRNA-seq) of >50 000 cells from mouse and human AITL samples revealed significant expansion of aberrant B cells, exhibiting properties of activating light zone (LZ)-like and proliferative dark zone (DZ)-like germinal center B (GCB) cells. The GCB cells in AITL clonally evolved with recurrent mutations in genes related to core histones. In silico network analysis using scRNA-seq data identified Cd40-Cd40lg as a possible mediator of GCB and tumor cell cluster interactions. Treatment of AITL model mice with anti-Cd40lg inhibitory antibody prolonged survival. The genes expressed in aberrantly expanded GCB cells in murine tumors were also broadly expressed in the B-lineage cells of TET2-mutant human AITL. Therefore, ACH-derived GCB cells could undergo independent clonal evolution and support the tumorigenesis in AITL via the CD40-CD40LG axis.