Follicular Dendritic Cell Immunohistochemical Markers in Angioimmunoblastic T-Cell Lymphoma

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.

Follicular dendritic cell sarcoma

Follicular dendritic cells (FDC) are mesenchymal-derived dendritic cells located in B-follicles where they play a pivotal role in triggering and maintaining B-cell adaptive immune response. In 1986 Dr. Juan Rosai first reported a series of neoplasms showing features of FDC and defined it as Follicular Dendritic Cell Tumor, subsequently renamed as "sarcoma" (FDCS). In its seminal and subsequent articles Rosai and colleagues highlighted the heterogeneous microscopic appearance of FDCS and its immunohistochemical and ultrastructural features.

FDCS mostly occurs in extranodal sites (79.4% of cases) and lymph nodes (15.1%); in about 7%-10% of cases it is associated with hyaline-vascular Castleman disease. Given its significant growth pattern and cytological variability, FDCS can be confused with various neoplasms and even inflammatory processes. The diagnosis requires the use of a broad spectrum of FDC markers (e.g. CD21, CD23, CD35, clusterin, CXCL13, podoplanin), particularly considering that tumor antigen-loss is frequent. The inflammatory-pseudotumor-like (IPT-like) variant of FDCS, in addition to its peculiar histopathological and clinical features, is characterized by positivity of tumor cells for Epstein-Barr virus, representing a diagnostic requisite.

No distinctive genetic and molecular anomalies have been identified in FDCS. It often carries an aberrant clonal karyotype and chromosomal structural alterations, frequently involving onco-suppressor genes. Direct or next generation sequencing showed alterations on genes belonging to the NF-κB regulatory pathway and cell-cycle regulators. In contrast to hematopoietic-derived histiocytic and dendritic cells tumors, FDCS typically lacks mutations in genes related to the MAPK pathway.

FDCS recurs locally in 28% and metastasizes in 27% of cases. Extent of the disease, surgical resectability and histopathological features are significantly associated with the outcome. IPT-like FDCS behaves as an indolent tumor, even if it often recurs locally over years.

Complete surgical excision is the gold standard of treatment. Data on targeted therapies (e.g.: tyrosine kinase inhibitors) or immune checkpoint inhibitors are very limited and responses are variable. A better understanding of the molecular drivers of this tumor may lead to potential new therapeutic strategies.

High-dimensional and single-cell transcriptome analysis of the tumor microenvironment in angioimmunoblastic T cell lymphoma (AITL)

Angioimmunoblastic T-cell lymphoma (AITL) is an aggressive lymphoid malignancy associated with a poor clinical prognosis. The AITL tumor microenvironment (TME) is unique, featuring a minority population of malignant CD4+ T follicular helper (TFH) cells inter-mixed with a diverse infiltrate of multi-lineage immune cells. While much of the understanding of AITL biology to date has focused on characteristics of the malignant clone, less is known about the many non-malignant populations that comprise the TME. Recently, mutational consistencies have been identified between malignant cells and non-malignant B cells within the AITL TME. As a result, a significant role for non-malignant populations in AITL biology has been increasingly hypothesized. In this study, we have utilized mass cytometry and single-cell transcriptome analysis to identify several expanded populations within the AITL TME. Notably, we find that B cells within the AITL TME feature decreased expression of key markers including CD73 and CXCR5. Furthermore, we describe the expansion of distinct CD8+ T cell populations that feature an exhausted phenotype and an underlying expression profile indicative of dysfunction, impaired cytotoxicity, and upregulation of the chemokines XCL2 and XCL1.

New preclinical models for angioimmunoblastic T-cell lymphoma: filling the GAP

Mouse models are essential to study and comprehend normal and malignant hematopoiesis. The ideal preclinical model should mimic closely the human malignancy. This means that these mice should recapitulate the clinical behavior of the human diseases such as cancer and therapeutic responses with high reproducibility. In addition, the genetic mutational status, the cell phenotype, the microenvironment of the tumor and the time until tumor development occurs, should be mimicked in a preclinical model. This has been particularly challenging for human angioimmunoblastic lymphoma (AITL), one of the most prominent forms of peripheral T-cell lymphomas. A complex network of interactions between AITL tumor cells and the various cells of the tumor microenvironment has impeded the study of AITL pathogenesis in vitro. Very recently, new mouse models that recapitulate faithfully the major features of human AITL disease have been developed. Here, we provide a summary of the pathology, the transcriptional profile and genetic and immune-phenotypic features of human AITL. In addition, we give an overview of preclinical models that recapitulate more or less faithfully human AITL characteristics and pathology. These recently engineered mouse models were essential in the evaluation of novel therapeutic agents for possible treatment of AITL, a malignancy in urgent need of new treatment options.

Identification of three subtypes of triple-negative breast cancer with potential therapeutic implications

Background

Heterogeneity and lack of targeted therapies represent the two main impediments to precision treatment of triple-negative breast cancer (TNBC), and therefore, molecular subtyping and identification of therapeutic pathways are required to optimize medical care. The aim of the present study was to define robust TNBC subtypes with clinical relevance.

Methods

Gene expression profiling by means of DNA chips was conducted in an internal TNBC cohort composed of 238 patients. In addition, external data (n = 257), obtained by using the same DNA chip, were used for validation. Fuzzy clustering was followed by functional annotation of the clusters. Immunohistochemistry was used to confirm transcriptomics results: CD138 and CD20 were used to test for plasma cell and B lymphocyte infiltrations, respectively; MECA79 and CD31 for tertiary lymphoid structures; and UCHL1/PGP9.5 and S100 for neurogenesis.

Results

We identified three molecular clusters within TNBC: one molecular apocrine (C1) and two basal-like-enriched (C2 and C3). C2 presented pro-tumorigenic immune response (immune suppressive), high neurogenesis (nerve infiltration), and high biological aggressiveness. In contrast, C3 exhibited adaptive immune response associated with complete B cell differentiation that occurs in tertiary lymphoid structures, and immune checkpoint upregulation. External cohort subtyping by means of the same approach proved the robustness of these results. Furthermore, plasma cell and B lymphocyte infiltrates, tertiary lymphoid structures, and neurogenesis were validated at the protein levels by means of histological evaluation and immunohistochemistry.

Conclusion

Our work showed that TNBC can be subcategorized in three different subtypes characterized by marked biological features, some of which could be targeted by specific therapies.

Electronic supplementary material

The online version of this article (10.1186/s13058-019-1148-6) contains supplementary material, which is available to authorized users.

Immunophenotyping of Sheep Paraffin-Embedded Peripheral Lymph Nodes

Sheep are not only a major livestock species globally, they are also an important large animal model for biomedical research and have contributed to our understanding of the ontogeny and architecture of the mammalian immune system. In this study, we applied immunohistochemistry and multicolor immunofluorescence in fixed and paraffin-embedded lymph nodes to phenotype the key populations of antigen presenting cells, lymphocytes, and stromal cells that orchestrate the host adaptive immune response. We used an extensive panel of antibodies directed against markers associated with dendritic cells (MHC class II, CD83, and CD208), macrophages (CD11b, CD163, and CD169), stromal cells (CNA.42, S100, and CD83), and lymphocytes (CD3, Pax5, CD4, CD8). Using different methods of tissue fixation and antigen retrieval, we provide a detailed immunophenotyping of sheep lymph nodes including the identification of potential subpopulations of antigen presenting cells and stromal cells. By characterizing cells expressing combinations of these markers in the context of their morphology and location within the lymph node architecture, we provide valuable new tools to investigate the structure, activation, and regulation of the sheep immune system in health and disease.

Use of Smooth Muscle Myosin Heavy Chain as an Effective Marker of Follicular Dendritic Cells

Smooth muscle myosin heavy chain (SMMHC) is a major structural component of the contractile apparatus in smooth muscle cells. Even though it is considered a relatively specific marker for terminal smooth muscle cell differentiation, expression in other cell types such as follicular dendritic cells (FDCs) has rarely been reported. To determine whether SMMHC represents an effective FDC marker in lymphoid tissues, we compared the immunohistochemical results for SMMHC with those of the traditional FDC markers podoplanin (D2-40) and CD21. Paraffin sections of 44 lymphoid tissues were analyzed, including 31 cases of follicular hyperplasia, 6 cases of follicular lymphoma, 2 cases of peripheral T-cell lymphoma, 3 cases of diffuse large B-cell lymphoma arising in follicular lymphoma, 1 case of nodular sclerosis classical Hodgkin lymphoma, and 1 case of small lymphocytic lymphoma. There was no statistically significant difference between the number of SMMHC-positive and D2-40-positive or CD21 lymph nodes (P>0.05). The extent and intensity of SMMHC-positive FDCs were similar to those of D2-40-positive FDCs (P=0.127 and 0.733, respectively), but significantly lower compared with those of CD21 cells (P=0.009 and 0.00002, respectively). However, in contrast to CD21 which was also positive in some germinal center B cells, SMMHC expression was restricted to FDCs. Our results indicate that SMMHC is an excellent marker for FDCs and can be particularly helpful in demonstrating the underlying architecture in lymphoid processes.

Angioimmunoblastic T-cell lymphoma: the many-faced lymphoma

Angioimmunoblastic T-cell lymphoma (AITL) is an uncommon subtype of mature peripheral T-cell lymphoma (PTCL). The history of AITL is much longer and deeper than the literature would suggest given the many names that have preceded it. Advanced-stage disease is common with uncharacteristic laboratory and autoimmune findings that often slow or mask the diagnosis. Significant strides in the immunohistochemical and molecular signature of AITL have brought increased ability to diagnose this uncommon type of PTCL. The 2016 World Health Organization classification of lymphoid neoplasms recently acknowledged the complexity of this diagnosis with the addition of other AITL-like subsets. AITL now resides under the umbrella of nodal T-cell lymphomas with follicular T helper phenotype. Induction strategies continue to focus on increasing complete remission rates that allow more transplant-eligible patients to proceed toward consolidative high-dose therapy and autologous stem cell rescue with improving long-term survival. There are several clinical trials in which recently approved drugs with known activity in AITL are paired with induction regimens with the hope of demonstrating long-term progression-free survival over cyclophosphamide, doxorubicin, vincristine, and prednisone. The treatment of relapsed or refractory AITL remains an unmet need. The spectrum of AITL from diagnosis to treatment is reviewed subsequently in a fashion that may one day lead to personalized treatment approaches in a many-faced disease.

Angioimmunoblastic T-cell lymphoma of the oral cavity presenting as gingival mass: report of the histopathologic and molecular characteristics of an unusual case featuring clonal T-cell receptor γ gene rearrangement by polymerase chain reaction

Angioimmunoblastic T-cell lymphoma (AITL) is a rare neoplastic process constituting 15% to 20% of peripheral T-cell lymphomas. We report the clinicopathologic and molecular characteristics of an unusual intraoral manifestation of AITL. A 35-year-old white man with a history of AITL presented with a 2.5-cm, poorly circumscribed, erythematous, exophytic lesion occupying the free and attached buccal gingiva of the right maxillary lateral incisor and canine. Histopathologically, the tumor showed diffuse and intense polymorphic infiltration by small to medium-sized lymphocytes admixed with numerous eosinophils. The neoplastic cells showed strong and diffuse reactivity for CD2, CD3, CD4, CD10, and PD-1 (programmed cell death 1 [PDCD1]). Rare immunopositivity was seen with BCL6 (B-cell CLL/lymphoma 6) and CXCL13 (chemokine [C-X-C motif] ligand 13). Neoplastic cells were negative for CD7 and EBER ISH (Epstein-Barr virus-encoded small RNA in situ hybridization). CD21 did not show any increased follicular dendritic cell component. Polymerase chain reaction-based assay found monoclonal T-cell receptor γ (TRG) gene rearrangements. Diagnosis of recurrent/residual AITL was rendered. Chemotherapy was administered, with the intraoral tumor resolving completely 3 months later.

Peripheral T-cell and NK-cell lymphomas and their mimics; taking a step forward - report on the lymphoma workshop of the XVIth meeting of the European Association for Haematopathology and the Society for Hematopathology

Mature T-cell and T/NK-cell neoplasms are both uncommon and heterogeneous, among the broad category of non-Hodgkin lymphomas. Owing to the lack of specific genetic alterations in the vast majority, most currently defined entities show overlapping morphological and immunophenotypic features, and therefore pose a challenge to the diagnostic pathologist. In the light of recent immunophenotypic, cytogenetic and molecular genetics advances in the field of T-cell and T/NK-cell lymphomas, the focus of the lymphoma workshop of the European Association for Haematopathology/Society for Hematopathology meeting in Lisbon, Portugal, in October 2012 was to refine existing diagnostic criteria and clarify the borders between overlapping entities. The panel reviewed over 200 submitted cases, which were grouped into five categories: (i) angioimmunoblastic T-cell lymphoma and T-follicular-helper-cell-associated lymphomas; (ii) CD30-positive T-cell lymphomas/lymphoproliferative diseases; (iii) extranodal T-cell and NK-cell neoplasms; (iv) EBV-associated T-cell/NK-cell lymphomas/lymphoproliferative diseases; and (v) peripheral T-cell lymphoma, not otherwise specified, post-transplant lymphoproliferative disorders, and mimics. This report summarizes the discussions and conclusions of the workshop, which question current diagnostic criteria and provide recommendations for refining existing classifications.

Follicular dendritic cells: origin, function, and different disease-associated patterns

Follicular dendritic cells (FDCs) are a specialized type of antigen-presenting dendritic cells that are largely restricted to lymphoid follicles. They form dense three-dimensional meshwork patterns within benign follicles, which maintain the follicular architecture. The FDC function is to bind and retain antigens by linking to complement and immune complexes and then present these antigens to germinal center B cells that start the secondary immune response. FDCs aid in the rescue of bound B cells from apoptosis, and induce the differentiation of B cells into long-term memory B cell clones or plasma cells. We will discuss the different patterns of the FDC meshwork observed in different types of reactive and neoplastic disorders, which may be due to underlying different roles that FDCs may play in these disorders and whether changes in the architecture of the FDC meshwork can be useful in routine diagnostic practice or have a prognostic value.

The spectrum of lymphoblastic, nodal and extranodal T-cell lymphomas: characteristic features and diagnostic dilemmas

T-cell lymphomas represent a heterogeneous group of neoplasms that encompass considerable clinical, morphologic, and immunophenotypic variation. The diagnosis of T-cell lymphoma is challenging because of its relative rarity, the lack of an immunophenotypic marker of clonality, and significant morphologic overlap with infectious/inflammatory processes and neoplasms, including Hodgkin and other non-Hodgkin lymphomas, and even mesenchymal or epithelial lesions. In the current World Health Organization classification of hematopoietic tumors, all except 1 subtype (ie, T-lymphoblastic lymphoma) are recognized as mature neoplasms derived from postthymic T cells. In addition to T-lymphoblastic lymphoma, this review will focus on nodal and extranodal T-cell lymphomas and exclude T-cell lymphomas presenting primarily in the skin. Extranodal natural-killer-cell/T-cell lymphoma, nasal type, will also be discussed because the derivation of this lymphoma from natural killer and natural killer-like T cells shows morphologic and immunophenotypic features that overlap with other T-cell lymphomas. In this review, we discuss the salient clinicopathologic, immunophenotypic, and genetic features, as well as our approaches to the diagnosis of lymphoblastic, nodal, and extranodal T-cell lymphomas.

Peripheral T-cell lymphoma with follicular T-cell markers

INTRODUCTION

Peripheral T-cell lymphomas (PTCLs) in western countries are uncommon tumors with unfavorable prognosis. They may be subclassified as anaplastic large-cell lymphomas (ALCLs), angioimmunoblastic-T-cell lymphomas (AITLs), or unspecified peripheral T-cell lymphomas (PTCLs-U). It has recently been demonstrated that AITLs originate from germinal center follicular helper T cells (TFH), whereas the normal counterparts of other PTCLs remain essentially unknown. The aim of this study was to establish whether other PTCL subgroups also express TFH cell markers.

MATERIALS AND METHODS

One hundred forty-six PTCLs were analyzed for programmed death-1 (PD-1) expression in tissue microarrays using a new monoclonal antibody called NAT-105. PD-1-positive cases, which did not fulfill all the criteria for AITL, were further evaluated in whole-tissue sections for another 12 immunohistochemical markers, including the TFH cell markers CXCL13, CD10, and BCL6. Clonal Ig and T-cell receptor rearrangements and Epstein-Barr virus-encoded RNA expression were also evaluated. Morphologic, clinical, and follow-up data were reviewed.

RESULTS

Twenty-five out of 87 non-AITL cases (28.75%) showed PD-1 immunostaining. CXCL13, BCL6, and CD10 expression was found in 24/25 (96%), 16/25 (64%), and 6/25 (24%) cases, respectively. All cases expressed at least 2 TFH cell markers. Moreover, 5 cases were positive for all 4 markers. Most cases (17/25, 68%) displayed some AITL-like features. Of the remainder, 1 was considered to be early AITL, 1 was diagnosed as ALCL-anaplastic lymphoma kinase-negative, and 4 of the other 6 PTCLs-U had morphology consistent with lymphoepithelioid (Lennert's) lymphoma. Three AITL-like cases showed IgH clonal rearrangement, 2 of which were associated with Epstein-Barr virus expression. Our series of patients did not differ significantly in their clinical presentation from most reported PTCL cases in the literature: 55% of them were alive and 35% were in complete remission after a median follow-up of 15 months after cyclophosphamide, dexorubicin, vincristine, and prednisone-based chemotherapy.

CONCLUSIONS

TFH cell markers, especially PD-1, were expressed in a subset of PTCLs not classified as AITL, although most of them shared some morphologic features with AITL. This suggests that the spectrum of AITL may be wider than previously thought, possibly including cases of lymphoepithelioid (Lennert's) lymphoma. Additionally, the results suggest that a subgroup of PTCLs-U, distinct from AITL and including some cases denominated as ALCL, may also be derived from TFH cells, although they develop along a distinct pathogenic pathway.