Germinal-Center T-Helper-Cell Markers PD-1 and CXCL13 Are Both Expressed by Neoplastic Cells in Angioimmunoblastic T-Cell Lymphoma

Extranodal NK/T-cell lymphoma, nasal type, includes cases of natural killer cell and αβ, γδ, and αβ/γδ T-cell origin: a comprehensive clinicopathologic and phenotypic study

Extranodal NK/T-cell lymphoma (ENKTL), nasal type, may be of NK or T-cell origin; however, the proportion of T-ENKTLs and whether they are of αβ or γδ type remains uncertain. To elucidate the cell of origin and detailed phenotype of ENKTL and assess any clinicopathologic associations, 67 cases of ENKTL from Thailand were investigated, together with 5 γδ enteropathy-associated T-cell lymphomas (EATLs) for comparison. In all, 70% of the ENKTL were T-cell receptor (TCR) β,γ and, in cases tested, δ negative (presumptive NK origin); 5% were TCR γδ, 3% were TCR αβ, 1% were TCR αβ/γδ, and 21% were indeterminate. Out of 17 presumptive NK-ENKTLs tested, 3 had clonal TCR rearrangements. All cases were EBV and TIA-1; >85% were positive for CD3, CD2, granzyme B, pSTAT3, and Lsk/MATK; and all were CD16. Presumptive NK-ENKTLs had significantly more frequent CD56 (83% vs. 33%) and CXCL13 (59% vs. 0%) but less frequent PD-1 (0% vs. 40%) compared with T-ENKTLs. Of the NK-ENKTLs, 38% were Oct-2 compared with 0% of T-ENKTLs, and 54% were IRF4/MUM1 compared with 20% of T-ENKTLs. Only αβ T-ENKTLs were CD5. Intestinal ENKTLs were EBV and had significantly more frequent CD30, pSTAT3, and IRF4/MUM1 expression but less frequent CD16 compared with γδ EATL. Significant adverse prognostic indicators included a primary non-upper aerodigestive tract site, high stage, bone marrow involvement, International Prognostic Index ≥2, lack of radiotherapy, Ki67 >40%, and CD25 expression. The upper aerodigestive tract ENKTLs of T-cell origin compared with those of presumptive NK origin showed a trend for better survival. Thus, at least 11% of evaluable ENKTLs are of T-cell origin. Although T-ENKTLs have phenotypic and some possible clinical differences, they share many similarities with ENKTLs that lack TCR expression and are distinct from intestinal γδ EATL.

Retrospective analysis of prognostic factors for angioimmunoblastic T-cell lymphoma: a multicenter cooperative study in Japan

Angioimmunoblastic T-cell lymphoma (AITL) is a major type of peripheral T-cell lymphoma (PTCL). To elucidate the clinicopathologic characteristics and prognosis of AITL in Japan, we retrospectively analyzed 207 patients with AITL. The median patient age was 67 years (range, 34-91 years), with 73% of patients older than 60 years. With a median follow-up of 42 months in surviving patients, 3-year overall survival (OS) was 54% and progression-free survival (PFS) was 38%. The International Prognostic Index (IPI) and the prognostic index for PTCL, not otherwise specified (PIT) were predictive for OS in this analysis. Multivariate analysis found that age older than 60 years, elevated white blood cell (WBC) and IgA levels, the presence of anemia and thrombocytopenia, and extranodal involvement at > 1 site were significant prognostic factors for OS, and IgA, anemia, and mediastinal lymphadenopathy were significant prognostic factors for PFS. A novel prognostic model consisting of the prognostic factors for OS was successfully constructed. In conclusion, IPI and PIT were still useful for prognostication of AITL, and other factors, including those not used in IPI, such as IgA, anemia, WBC count, thrombocytopenia, and mediastinal lymphadenopathy, also significantly affected prognosis. Future investigations for IgA as a unique prognostic factor are warranted.

The B7 homologues and their receptors in hematologic malignancies

The B7 homologues and their receptors regulate both peripheral tolerance and adaptive immunity. This field is rapidly evolving as new ligands and receptors are being identified. Much of the work supporting their role in the regulation of host anti-tumor immunity has been derived from experimental models and clinical trials in solid malignancies. However, a growing body of evidence demonstrates that the B7-H family has important immunologic and non-immunologic functions in a variety of hematologic malignancies. Herein, we will review recent evidence that supports the therapeutic targeting of the B7 homologues in hematologic malignancies.

Three different expression patterns of T-bet in angioimmunoblastic T-cell lymphoma

Angioimmunoblastic T-cell lymphoma (AITL) exhibits a multifaceted clinical picture and distinct architectural patterns that correlate with disease progression and the number of neoplastic cells. In this study we investigated the expression of the transcription factor T-bet and correlated it with the architectural patterns in 29 cases of AITL. Double immunolabelings for T-bet, CD20, CD3 or PD1 revealed the following patterns: predominant T-bet expression by neoplastic T-cells (A), by aggregates of small B-cells (B) or by B-immunoblasts (C). The majority of cases of AITL pattern II showed a T-bet expression pattern B (6/8 cases), while the majority of those with pattern III exhibited the T-bet pattern A (11/21 cases). We propose that T-bet expression by B-cells represents a T-cell independent immune response trying to cope with opportunistic infections, while T-bet expression by neoplastic T-cells is linked to the introduction of a Th17 response responsible for the immunologic derangements characteristic of AITL.

Pathology and biology of peripheral T-cell lymphomas

Peripheral T-cell lymphomas (PTCLs) represent a heterogeneous group of more than 20 neoplastic entities derived from mature T cells and natural killer (NK) cells involved in innate and adaptive immunity. With few exceptions these malignancies, which may present as disseminated, predominantly extranodal or cutaneous, or predominantly nodal diseases, are clinically aggressive and have a dismal prognosis. Their diagnosis and classification is hampered by several difficulties, including a significant morphological and immunophenotypic overlap across different entities, and the lack of characteristic genetic alterations for most of them. Although there is increasing evidence that the cell of origin is a major determinant for the delineation of several PTCL entities, however, the cellular derivation of most entities remains poorly characterized and/or may be heterogeneous. The complexity of the biology and pathophysiology of PTCLs has been only partly deciphered. In recent years, novel insights have been gained from genome-wide profiling analyses. In this review, we will summarize the current knowledge on the pathobiological features of peripheral NK/T-cell neoplasms, with a focus on selected disease entities manifesting as tissue infiltrates primarily in extranodal sites and lymph nodes.

A case report of angioimmunoblastic T cell lymphoma (AITL) with localization of neoplastic clear cells in the outer zone of germinal centers

Angioimmunoblastic T cell lymphoma (AITL) is characterized by the presence of atypical lymphocytes with clear cytoplasm and follicular dendritic cells, arborization of high endothelial blood vessels, and infiltration by inflammatory cells, such as epithelioid histiocytes, eosinophils, immunoblasts, and plasma cells. The neoplastic clear cells are localized around the high endothelial blood vessels or interfollicular areas. Recent reports have suggested that these neoplastic clear cells originate from helper T cells in germinal centers, based on their expression of CD10, PD-1, and CXCL13. We experienced a case of AITL which is histologically unique. A 61-year-old male presented to our hospital (Ogaki Municipal Hospital) with edema of his lower legs. Inguinal lymph node biopsy revealed that neoplastic clear T cells were mainly localized in the outer zone of germinal centers, specifically within the follicular dendritic cell (FDC) meshwork. Moreover, these cells were positive for CD3, CD4, CD10, CD43, CD45RO, PD-1, and weakly positive for CXCL-13. This is the first report showing that the neoplastic clear T cells were localized in the outer zone of germinal centers morphologically as well as immunohistochemically. In conclusion, this case report further supports the notion of germinal center helper T cell origin of neoplastic clear cells in AITL.

Sequential development of diffuse large B-cell lymphoma in a patient with angioimmunoblastic T-cell lymphoma

Lymphoma of different histologic type can occur in the same patient. Here, we describe a 64-year-old male patient with angioimmunoblastic T-cell lymphoma (AITL) who subsequently developed diffuse large B-cell lymphoma (DLBCL). At the time of initial diagnosis, histologic examination of a left inguinal lymph node of the patient and a monoclonal pattern of TCRβ gene rearrangement showed typical features of AITL, and there was no evidence of a monoclonal B-cell population. Twenty-six months later, he had generalized lymphadenopathy and organs involvement by DLBCL. A monoclonal IgH gene rearrangement proved de novo development of secondary B-cell lymphoma and excluded relapse of a primary composite lymphoma. The in situ hybridization analysis showed Epstein-Barr-encoded RNA (EBER) sporadic positivity in sample collected from AITL but extensive positivity in the immunoblasts collected from DLBCL. Our observation supports the hypothesis that Epstein-Barr virus (EBV) is etiologically related to AITL in this case. Clonal expansion of EBV-associated DLBCL is a secondary event in AITL via EBV infection or reactivation.

Expression of follicular helper T cell markers in nodal peripheral T cell lymphomas: a tissue microarray analysis of 162 cases

Aims

To evaluate the role of the follicular helper T (TFH) cell markers, CD10, BCL6, programmed death-1 (PD-1) and CXCL13, in the differential diagnosis of nodal peripheral T cell lymphomas (PTCLs) and to determine whether PTCL subtypes other than angioimmunoblastic T cell lymphoma (AITL) express TFH cell markers.

Methods

162 nodal PTCL specimens and 53 other lymphoid pathology specimens were collected. Immunohistochemistry for CD10, BCL6, PD-1 and CXCL13 was performed on tissue microarray sections. Morphological feature analysis and double labelling assay were also performed.

Results

For AITL cases, the rate of CD10, BCL6, PD-1 and CXCL13 expression was 75.0% (36/48), 66.7% (32/48), 93.8% (45/48) and 97.9% (47/48), respectively. Expression of CD10, PD-1 and CXCL13 in the AITL group was significantly higher than in other nodal PTCLs and the control group (p<0.05). The rate of coexpression of three or four (≥3) markers was 83.3% for AITL cases, which was significantly higher than that for any of the non-AITL cases (0–4.9%; p<0.05). The rate of coexpression of PD-1 and CXCL13 (91.7%, 44/48) was significantly higher than that of CD10 and BCL6 (56.3%, 27/48) (p=0.000) in the AITL group. Seventeen cases of PTCL not otherwise specified (PTCL, NOS) expressed CXCL13, including both cases of the follicular variant of PTCL, NOS (FVPTCL, NOS), three of the four cases of the lymphoepithelioid variant of PTCL, NOS (LVPTCL, NOS), and the remaining 12 cases which displayed one or more features of AITL.

Conclusions

The combined detection of CD10, BCL6, PD-1 and CXCL13 has high specificity and sensitivity for the differential diagnosis of AITL. PD-1 and CXCL13 are more sensitive, superior diagnostic markers for AITL than CD10 and BCL6. Currently, TFH cell markers are the only available markers that show high specificity for AITL. LVPTCL, NOS and/or FVPTCL, NOS may also arise from TFH cells and fall within the spectrum of AITL.

CD200 (OX-2 membrane glycoprotein) expression in b cell-derived neoplasms

We studied the expression of CD200, an immunoglobulin superfamily membrane glycoprotein, in a wide range of B cell-derived neoplasms by immunohistochemical staining of paraffin-embedded tissue sections. In addition to chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL), CD200 is expressed in other B-cell lymphoproliferative disorders, including hairy cell leukemia. In addition, neoplastic cells in classical Hodgkin lymphoma are immunoreactive for CD200. CD200 was previously reported to be expressed in acute myeloid leukemia, and we find that it is also expressed in B-lymphoblastic leukemia/lymphoma. We conclude that CD200 may be a useful immunophenotypic marker in the evaluation of B cell-derived neoplasms. Furthermore, since an anti-CD200 immunotherapeutic agent is in clinical trials, a number of B cell-derived neoplasms in addition to CLL/SLL may be suitable therapeutic targets.

A practical approach to the flow cytometric detection and diagnosis of T-cell lymphoproliferative disorders

The flow cytometric analysis of T-cell malignancies is difficult due to the heterogeneity of T-cells and the lack of convenient methods to detect T-cell clonality. Neoplastic T-cells are most often detected by their altered level of surface antigen expression, and detection requires an extensive knowledge of the phenotype of normal T-lymphocytes. This review focuses on the methods to distinguish malignant T-cells from their normal counterparts and the phenotypic features of the T-cell lymphoproliferative disorders.

PD-1 expression in T-cell lymphomas and reactive lymphoid entities: potential overlap in staining patterns between lymphoma and viral lymphadenitis

Peripheral T-cell lymphomas are a heterogeneous group that often requires the use of ancillary testing for accurate diagnosis. This is particularly applicable to the diagnosis of angiommunoblastic T-cell lymphoma (AITL) and peripheral T-cell lymphoma, unclassified (PTCLU), because of their histologic and immunophenotypic overlap with reactive lymphoid proliferations. Recently, immunohistochemistry for programmed death-1 (PD-1), a marker of follicular helper T cells, was shown to be sensitive in the detection of AITL and PTCLU. The sensitivity of this marker in reactive entities, however, has not been adequately evaluated. We confirm that PD-1 staining is a highly sensitive marker in the diagnosis of peripheral T-cell lymphomas: increased extrafollicular PD-1-positive cells were seen in 93% (76/82) of AITL, 62% (16/26) of PTCLU, and 11% (2/18) of anaplastic-lymphoma-kinase (ALK)-negative anaplastic large-cell lymphomas. The majority of reactive lymphadenopathies including Cat-scratch disease, Kikuchi lymphadenitis, Castleman disease, and reactive follicular hyperplasia showed no PD-1 staining outside follicles. Some reactive lymph nodes, showed increased extrafollicular PD-1-positive cells in a pattern similar to AITL and PTCLU, and include progressive transformation of germinal centers, viral lymphadenitis (Epstein-Barr virusand human immunodeficiency virus) and Rosai-Dorfman disease. This study shows that PD-1-positive cells may be increased in a number of settings other than T-cell lymphomas. We conclude that staining for PD-1 in reactive and atypical lymphadenopathies should be interpreted with caution and in the context of other ancillary immunophenotypic and molecular studies before a diagnosis of AITL or PTCLU is entertained.