CD20+ T-cell lymphoma. Neoplastic transformation of a normal T-cell subset

Nodal T follicular helper cell lymphoma with aberrant CD20 expression and monoclonal TCR, IG rearrangements secondary to Classical Hodgkin Lymphoma: a case report

Classical Hodgkin Lymphoma (CHL) is a rare malignant neoplasm of the lymphatic system. While CHL typically responds well to conventional treatments, some cases may experience relapse to other subtypes, with the development of secondary peripheral T-cell lymphoma (PTCL) being relatively uncommon. Herein, we report a rare case of nodal T follicular helper cell lymphomas,nos (nTFHL-NOS) secondary to CHL, accompanied by aberrant CD20 expression and clonal rearrangements of T-cell receptor (TCR) and immunoglobulin (IG). A 74-year-old male, was diagnosed with CHL, leaning toward the mixed cell type, 6 years ago. He received six cycles of the Adriamycin, Bleomycin, Vinblastine, Dacarbazine (ABVD) regimen, achieving complete clinical remission. The patient was admitted to our hospital due to the appearance of multiple skin nodules 66 months later. Histopathological analysis revealed nTFHL-NOS, with aberrant CD20 expression and clonal rearrangements of TCR and IG. The patient underwent two cycles of chemotherapy with brentuximab vedotin and the Gemcitabine-Oxaliplatin (G-mox) regimen, resulting in a reduction of the skin lesions to 2 cm × 1 cm. We discuss this rare case and review related literature.

The role of CD20+ T cells: Insights in human peripheral blood

CD20+ T cells constitute a small subset of T cells. These are found among CD4+, CD8+, CD4+CD8+, CD4-CD8- T, and TCRγδ+ T cells, and have been poorly characterized. The aim of this study was to characterize peripheral blood (PB) CD20+ T cells and compare them to their PB CD20- T cell counterparts. PB from 17 healthy individuals was collected. The distribution of CD20+ T cells among maturation-associated T cells compartments (naïve, central memory, transitional memory, effector memory, and effector T cells), their polarization, activation status, and expression of immune-regulatory proteins were evaluated by flow cytometry. Their function was also assessed, by measuring IFN-γ, TNF-α, and IL-17 production. Compared with CD20- T cells, CD20+ T cells represent a higher proportion of transitional memory cells. Furthermore, CD20+ T cells display a proinflammatory phenotype, characterized by the expansion of Th1, Th1/17, and Tc1 cell subsets , associated to a high expression of activation (CD25) and exhaustion (PD-1) markers. In addition, the simultaneous production of the proinflammatory cytokines IFN-γ, TNF-α, and IL-17 was also detected in CD4+CD20+ T cells. Our results show that CD20+ T cells are phenotypically and functionally different from CD20- T cells, suggesting that these cells are a distinct subset of T cells.

A biphenotypic lymphocyte subset displays both T- and B-cell functionalities

T cell/B cell mixed phenotypic lymphocytes have been observed in different disease contexts, yet their presence and function in physiological conditions remain elusive. Here, we provide evidence for the existence of a lymphocyte subset endogenously expressing both T- and B-cell lineage markers in mice. The majority of these T/B phenotypic lymphocytes (CD3+CD19+) show an origin of pro/pre B cells and distribute widely in mouse bone marrow, lymph nodes, spleen, and peripheral blood. Functional assays show that these biphenotypic lymphocytes can be activated through stimulating TCR or BCR signaling pathways. Moreover, we show that these cells actively participate both the humoral and cellular immune responses elicited by vaccination. Compared to conventional T cells, these biphenotypic lymphocytes can secrete a higher level of IL-2 but a lower level of TNF-α upon antigen specific stimulation. An equivalent lymphocyte subset is found in freshly isolated human PBMCs and exhibits similar functionality, albeit at a lower frequency than in mice.

Immunohistochemical identification of T and B lymphocytes in formalin-fixed, paraffin-embedded tissues of 53 avian species using commercial antibodies

Providing a method to detect avian lymphocytes by immunohistochemistry (IHC) would be helpful for analyzing immune function and diagnosing diseases in birds. In this study, we comprehensively examined the immunohistochemical identification of avian T and B lymphocytes in formalin-fixed, paraffin-embedded tissues from 53 avian species across 15 orders, using eight commercially available lymphocyte markers. T lymphocytes from all 53 avian species tested were specifically detected by IHC using the anti-CD3 antibody (clone F7.2.38). The appropriate antibody for detecting avian B lymphocytes in IHC varied depending on the avian species. B lymphocytes were specifically labeled by IHC in 46 of 53 avian species (86.8%) using any of seven B cell markers. The anti-PAX5 antibody (clone SP34) immunohistochemically detected B lymphocytes from the majority of avian species (41 out of 53 species), excluding those in the orders Falconiformes (falcons) and Passeriformes (oscines). The anti-BAFF-R antibody (clone 2C4) proved suitable for detecting B lymphocytes in the orders Galliformes (landfowls) and Anseriformes (waterfowls) in IHC. Caution is advised when using the anti-BLA36 (clone A27-42) and two anti-CD20 (clone L26 and product No. PA5-16701) antibodies, which are commonly used as B cell markers in mammals, for detecting avian B lymphocytes. These antibodies reacted with cells located in both T and B cell areas in certain avian species. The anti-Bu-1a/b (clone AV20) and anti-CD79a (clone HM57) antibodies were found not to bind to B lymphocytes in various avian species in IHC.

Transdifferentiation, phenotypic infidelity, progression, and transformation in T/NK-cell neoplasms: Report from the 2021 SH/EAHP Workshop

OBJECTIVES

Sessions 8 and 9 of the 2021 Society for Hematopathology and the European Association for Haematopathology Workshop aimed to collect examples of transdifferentiation, lineage infidelity, progression, and transformation in precursor and mature T/natural killer (NK)-cell neoplasms.

METHODS

Twenty-eight cases were submitted and analyzed, with whole-exome sequencing and genome-wide RNA expression analysis performed in a subset of the cases.

RESULTS

In session 8, 7 T-lymphoblastic lymphoma/leukemia cases were received that showed transdifferentiation to clonally related mature myeloid hematopoietic neoplasms, including 6 histiocytic/dendritic cell lineage neoplasms and a mast cell sarcoma. Session 9 included 21 mature T-cell neoplasms that were grouped into 3 themes. The first one addressed phenotypic infidelity in mature T-cell lymphomas (TCLs) and included 8 TCLs expressing aberrant antigens, mimicking classic Hodgkin and non-Hodgkin B-cell lymphomas. The second theme addressed disease progression in TCL and included 5 cutaneous T-cell lymphoproliferative disorders and 2 T-cell large granular lymphocyte proliferations with subsequent progression to systemic TCL. The third theme included 6 patients with TCL with T-follicular helper phenotype, mainly angioimmunoblastic T-cell lymphoma, with concurrent/subsequent clonal hematopoiesis or myeloid neoplasms and/or subsequent/concomitant diffuse large B-cell lymphoma.

CONCLUSIONS

This cohort of cases allowed us to illustrate, discuss, and review current concepts of transdifferentiation, aberrant antigen expression, and progression in various T/NK-cell neoplasms.

CD20-positive subcutaneous panniculitis-like T-cell lymphoma presenting as polycranial neuropathy: A CARE-compliant case report and literature review

BACKGROUND

Subcutaneous panniculitis-like T-cell lymphoma(SPTCL) is a very rare cytotoxic T-cell skin lymphoma involving subcutaneous tissue, and mainly affects young females. T-cell phenotype is characterized by CD3+, CD8+, and CD4-. SPTCT with polycranial neuropathy has rarely been described. SPTCL is believed to show an indolent clinical course unless patients develop haemophagocytic syndrome or sudden respiratory failure. Its treatment has not been established yet.

CASE PRESENTATION

We report a case of intractable SPTCT in a 66-year-old woman with multiple cranial nerve palsies and diabetes. She showed involvement of the bilateral facial nerve, left trigeminal nerve, left auditory nerve, and right oculomotor nerve. The single inconspicuous skin lesion in the trunk presented with an erythematous nodule with a diameter of <5 cm and a slightly pink infiltrated plaque. Electromyography revealed bilateral damage to the facial nerve. Differential immunohistochemical characteristics were observed. Immunohistochemistry demonstrated diffuse CD20 positivity. Cerebral spinal fluid analysis revealed elevated protein levels of 0.92 (0.15-0.45) g/L. Her condition regressed severely over time. She was treated with chemotherapy but died 10 months later, the probable cause of death was lung involvement.

CONCLUSION

The patient's involvement with the central nervous system may be associated with positivity for CD20. Molecular biomarkers may act as therapeutic targets for SPTCL.

CD20+ T cells: an emerging T cell subset in human pathology

Introduction

Although CD20 is classically a B cell marker, in the last three decades, dim expression has been noted on a subset of T cells as well that has been independently verified by a number of groups. Our understanding of these cells and their function is not well established.

Methods

A thorough review of original articles on CD20⁺T cells was undertaken of Pubmed by using combination of phrases including “CD20⁺”, “CD20-positive” and “T cells”. Articles in English were considered, and there was no time restriction.

Results

CD20⁺T cells express the standard T cell markers and, in comparison to CD20¯ T cells, appear to express greater inflammatory cytokines and markers of effector function. Although the ontogeny of these cells is still being established, the current theory is that CD20 may be acquired by trogocytosis from B cells. CD20⁺T cells may be found in healthy controls and in a wide range of pathologies including autoimmune diseases, haematological and non-haematological malignancies and human immunodeficiency virus (HIV) infections. One of the best studied diseases where these cells are found is multiple sclerosis (MS) where a number of therapeutic interventions, including anti-CD20 depletion, have been shown to effectively deplete these cells.

Conclusion

This review summarises the latest understanding of CD20⁺T cells, their presence in various diseases, their putative function and how they may be an ongoing target of CD20-depleting agents. Unfortunately, our understanding of these cells is still at its infancy and ongoing study in a wider range of pathologies is required.

Nodal T-zone lymphoma and T-zone hyperplasia in dogs

T-zone lymphoma (TZL) is an indolent, nodal lymphoma that has been clinically characterized in detail in dogs, and T-zone hyperplasia (TZH) is a hyperplastic change in lymph nodes associated with antigen processing. In some cases, histopathological features of TZL and TZH are similar, and are difficult to differentiate by morphology alone. Since there have been few publications characterizing their immunohistochemical profiles, histological, immunohistochemical, and clonality examinations were performed using formalin-fixed paraffin-embedded samples of canine lymph nodes with TZL (14 cases) and canine lymph nodes with TZH associated with nonlymphocytic tumors (10 cases). Immunohistochemically, small- to medium-sized lymphocytes of TZL were immunopositive for CD3, CD5, and HLA-DR, and negative for CD45, FOXP3, and granzyme B (GRB) in all cases. Among these 14 cases, 11 were immunopositive for CD8 and 1 was CD20 positive. Paracortical lymphocytes in TZH were diffusely immunopositive for CD3, CD5, and CD45, with scattered immunopositivity for CD8, HLA-DR, FOXP3, and GRB, and negative for CD20 in all cases. A clonal TCR gene rearrangement was detected in 13/14 TZL and none of the TZH cases. The present study revealed that TZL is a clonal proliferation of monomorphic CD8+CD45-GRB- T cells, while TZH consists of an immunophenotypically heterogenous population of CD45+ T cells that are variably positive for CD8 and FOXP3. These results suggest that canine TZL is a clonal proliferation of naïve or premature cytotoxic T cells. Regarding TZH, variable immunopositivity for cytotoxic and regulatory T-cell antigens may reflect immune responses to a variety of regional neoplastic lesions.

Gamma-Delta and CD20 Mycosis Fungoides: Two Cases Uncovered by Broad-Spectrum Immunostaining

ABSTRACT

Mycosis fungoides (MF) expresses T-cell markers and the alpha-beta T-cell receptor (TCR) complex. Here, we describe a case of MF with dual expression of TCR delta and TCR beta and a case of MF expressing the B-cell marker CD20. Both anomalies were detected after we instituted a broad-spectrum immunostaining panel for cutaneous T-cell lymphomas. These findings suggest anomalous immunophenotypes may be more common in MF than previously appreciated. Histopathologists should be aware of unexpected malleability in the immunophenotype of MF to avoid confusion with other subtypes of cutaneous lymphoma. Further research into the prevalence and significance of CD20 and TCR-delta expression in MF is encouraged.

Rituximab Plus Chemotherapy Provides No Clinical Benefit in a Peripheral T-Cell Lymphoma Not Otherwise Specified with Aberrant Expression of CD20 and CD79a: A Case Report and Review of the Literature

Peripheral T-cell lymphoma, not otherwise specified (PTCL-NOS) is the most common entity of mature T-cell neoplasms. PTCL-NOS generally has an aggressive behavior and is often refractory to standard therapy. Only a few cases of PTCL with aberrant expression of B-cell antigens have been reported so far. This phenotypic aberrancy may lead to misdiagnosis as B-cell non-Hodgkin lymphomas and eventual inappropriate patient management, whereas in an accurately diagnosed PTCL, the presence of CD20 may appear as an appealing therapeutic target. In this setting, response to anti-CD20 monoclonal antibody in combination with chemotherapy has been poorly explored. We describe the case of a 59-year-old male diagnosed by a pathological and molecular approach as PTCL-NOS with aberrant co-expression of the B-cell antigens CD20 and CD79a, which proved non-responsive to the addition of rituximab to standard polychemotherapy. This case highlights that the presence of CD20 in PTCL may be misleading in the diagnosis and also act as a lure for the clinician to adopt a rituximab-based treatment, the effectiveness of which is undefined as the molecular mechanisms underlying B-cell marker expression in PTCL.

CD20-positive extranodal NK/T cell lymphoma: clinicopathologic and prognostic features

Extranodal natural killer (NK)/T cell lymphoma (ENKTCL) with aberrant CD20 expression is extremely rare. Here, we describe the clinicopathologic features of 11 CD20-positive ENKTCLs from three institutions in China along with a literature review. Membranous expression of CD20 was identified in 1.29% (11/851) of ENKTCLs. CD20-positive ENKTCLs primarily occurred in extra-nasal sites (72.2%, 13/18) rather than in the nasal cavity (27.8%, 5/18). Most evaluated patients (71.4%, 10/14) presented ENKTCL at advanced stage IV. The percentage of CD20-positive tumor cells ranged from 20 to 90%, and the CD20 staining intensity was dimmer in tumor cells than in normal B cells. Among four cases with multiple biopsies, three cases showed discordant expression of CD20 between the disseminated and primary lesions. All evaluated cases were negative for other B cell markers, including PAX5, CD79a, and CD19, except for one case that showed focally positive for CD79a. Patients with CD20-positive ENKTCL more frequently had advanced diseases (stage III/IV: 70% vs 17%, p = 0.001), with older age (median age at diagnosis: 60 years vs. 43.5 years, p = 0.006) and had inferior outcome (median survival: 18.7 moths vs 36.0 moths, p = 0.017) compared with CD20-negative cases. Four nonsynonymous single nucleotide variants (C > T) and one stop-gain mutation (C > T) in the exonic region of CD20 gene (MS4A1) were detected in one of seven cases with target region next-generation sequencing. Thus, ENKTCL with aberrant CD20 expression is rare, tends to occur in older patients, and is characterized by a highly aggressive clinical course and poor outcomes. The mechanism underlying the expression of CD20 in ENKTC still remains unknown.

CD20-positive primary nasal peripheral T-cell lymphoma: An analysis of one case and review of the literature

CD20-positive T-cell lymphoma (TCL) is a very rare disease entity that is associated with the co-expressions of a range of T cell lineage makers, such as, CD2, CD3, CD5, or CD7, and CD20. The biological and clinical significance of CD20 antigen expressed in TCL has been unclear. Here, we are reporting an unusual case of CD20-positive primary nasal peripheral T-cell lymphoma, not otherwise specified (PTCL-NOS) in a 62-year-old female with both peripheral blood (PB) and bone marrow (BM) involvement. Flow cytometry (FC) analysis revealed CD20+ lymphoma cells in PB, BM, and lymph node (LN) and was consistent with pathological findings. FC immunophenotyping was proved of great diagnostic contribution.

Transcriptional Analysis of Lennert Lymphoma Reveals a Unique Profile and Identifies Novel Therapeutic Targets

Lennert lymphoma (LL) is a lymphoepithelioid morphological variant of peripheral T-cell lymphoma-not otherwise specified (PTCL/NOS), clinically characterized by better prognosis if compared with other PTCL/NOS. Although well characterized as far as morphology and phenotype are concerned, very little is known regarding its molecular features. In this study, we investigated the transcriptional profile of this tumor aiming 1) to identify its cellular counterparts; 2) to better define its relation with other PTCLs-and, therefore, its possible position in lymphoma classification; and 3) to define pathogenetic mechanisms, possibly unveiling novel therapeutic targets. To address these issues, we performed gene and microRNA expression profiling on LL and other PTCL/NOS cases; we identified different genes and microRNAs that discriminated LL from other PTCL/NOS. Particularly, LL revealed a molecular signature significantly enriched in helper function and clearly distinguishable from other PTCL/NOS. Furthermore, PI3K/Akt/mTOR pathway emerged as novel potential therapeutic target. In conclusion, based on the already known particular morphological and clinical features, the new molecular findings support the hypothesis that LL might be classified as a separate entity. Preclinical and clinical studies testing the efficacy of PI3K/MTOR inhibitors in this setting are warranted.

STAT6 phosphorylation upregulates microRNA-155 expression and subsequently enhances the pathogenesis of chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL), a clonal expansion of CD5⁺ B cells, is the most common form of adult leukemia; however, the molecular mechanisms underlying its pathogenesis remain undetermined. It has been previously suggested that numerous biological factors, including cytokines, may be involved in the proliferation of malignant cells. For example, interleukin (IL)-4, IL-2, interferon-γ and tumor necrosis factor serve roles as inhibitors of cellular apoptosis; whereas IL-5 and IL-10 are inducers of cellular apoptosis. In the present study, the results demonstrated that the phosphorylation and activation of signal transducer and activator of transcription 6 (STAT6) was induced by IL-4 in a time-dependent manner. Notably, the expression level of microRNA (miR)-155 was increased in MEC-1 cells following treatment with IL-4; however, this effect was attenuated following STAT6 knockdown via RNA interference. In addition, STAT6 knockdown promoted cell apoptosis, which was partly attenuated by treatment with IL-4. Inhibition of miR-155 expression significantly increased cell apoptosis despite the presence of IL-4. The results of the present study suggested that treatment with IL-4 enhanced the expression of miR-155, which regulated CLL cell survival via the enhanced phosphorylation of STAT6.

CD3+CD20+ T cells and their roles in human diseases

CD3⁺CD20⁺ T cells are a population of CD3⁺ T cells co-expressing CD20 that make up to ∼3-5% of the CD3⁺ T-cell compartment in the peripheral blood of human beings. In healthy individuals, CD3⁺CD20⁺ T cells are heterogeneous for containing a lower proportion of CD4⁺ cells, but produce higher levels of IL-17A and/or IFN-γ than those of CD3⁺CD20^- T cells. Recently, emerging studies have shown a pathogenic behavior of CD3⁺CD20⁺ T cells in autoimmune diseases and CD20⁺ T-cell malignancies, and patients with the diseases may benefit from anti-CD20 immunotherapy to deplete these cells. However, CD3⁺CD20⁺ T cells may also play a protective role in ovarian cancer and HIV infection for their strong propensity to IFN-γ production. In this review, we will describe the current knowledge about CD3⁺CD20⁺ T-cell biology, and discuss their functional roles in autoimmune diseases as well as cancer and infectious diseases.

Rituximab treatment for chronic steroid-dependent Henoch-Schonlein purpura: 8 cases and a review of the literature

BACKGROUND

Henoch-Schonlein purpura (HSP) is a small vessel vasculitis that is characterized by non-thrombocytopenic purpura, abdominal pain, arthritis, and glomerulonephritis. Typically, HSP is self-limited requiring only supportive care, but more severe cases may require corticosteroid (CS) treatment. Rarely, a subset of these patients has persistent rash, arthritis, abdominal involvement, or renal disease despite treatment with CS, or has disease recurrence on CS tapering. Refractory HSP has been effectively treated with a variety of CS sparing therapies. For life-threatening refractory HSP, the B cell depleting agent, rituximab (RTX), has been reported as beneficial for children with substantial renal or central nervous system involvement. However, RTX use for children with less severe HSP, but chronic CS dependent disease refractory to CS sparing immunomodulatory agents, has been less well explored. Herein, we describe 8 children treated with RTX for chronic refractory HSP and report a reduction in recurrent hospitalizations and eventual CS discontinuation.

METHODS

This is a retrospective analysis of eight children who were treated with RTX for chronic CS dependent HSP during the years 2006-2014 at a single institution. A chart review of the electronic medical record was performed to determine the presenting symptoms, the type and duration of treatment received, and the number of hospitalizations prior to and after RTX. The number of hospitalizations and oral corticosteroid burden were analyzed using the Wilcoxon signed rank test.

RESULTS

Prior to receiving RTX, seven patients had at least one hospitalization for HSP (median 1.5, range 0-3). Following RTX, only two patients were hospitalized, each a single time for recurrent abdominal pain. The median oral CS burden was 0.345 mg/kg/day before RTX and 0 mg/kg/day at 6 months (p = 0.078), 1 year (p = 0.0625), and 2 years (p = 0.03) following RTX infusion. Seven out of eight children met remission criteria, defined as no active rash, arthritis, nephritis (hematuria and proteinuria), or gastrointestinal distress following RTX. No serious adverse events were noted.

CONCLUSION

Overall, RTX effectively reduced the number of hospital admissions and oral CS burden. RTX also helped most all children achieve clinical remission. RTX appears to be an effective and safe alternative for chronic CS dependent and immunomodulatory refractory childhood HSP.

Feline low-grade alimentary lymphoma: an emerging entity and a potential animal model for human disease

BACKGROUND

Low-grade alimentary lymphoma (LGAL) is characterised by the infiltration of neoplastic T-lymphocytes, typically in the small intestine. The incidence of LGAL has increased over the last ten years and it is now the most frequent digestive neoplasia in cats and comprises 60 to 75% of gastrointestinal lymphoma cases. Given that LGAL shares common clinical, paraclinical and ultrasonographic features with inflammatory bowel diseases, establishing a diagnosis is challenging. A review was designed to summarise current knowledge of the pathogenesis, diagnosis, prognosis and treatment of feline LGAL. Electronic searches of PubMed and Science Direct were carried out without date or language restrictions.

RESULTS

A total of 176 peer-reviewed documents were identified and most of which were published in the last twenty years. 130 studies were found from the veterinary literature and 46 from the human medicine literature. Heterogeneity of study designs and outcome measures made meta-analysis inappropriate. The pathophysiology of feline LGAL still needs to be elucidated, not least the putative roles of infectious agents, environmental factors as well as genetic events. The most common therapeutic strategy is combination treatment with prednisolone and chlorambucil, and prolonged remission can often be achieved. Developments in immunohistochemical analysis and clonality testing have improved the confidence of clinicians in obtaining a correct diagnosis between LGAL and IBD. The condition shares similarities with some diseases in humans, especially human indolent T-cell lymphoproliferative disorder of the gastrointestinal tract.

CONCLUSIONS

The pathophysiology of feline LGAL still needs to be elucidated and prospective studies as well as standardisation of therapeutic strategies are needed. A combination of conventional histopathology and immunohistochemistry remains the current gold-standard test, but clinicians should be cautious about reclassifying cats previously diagnosed with IBD to lymphoma on the basis of clonality testing. Importantly, feline LGAL could be considered to be a potential animal model for indolent digestive T-cell lymphoproliferative disorder, a rare condition in human medicine.

Immunohistochemical Profiling of Canine Intestinal T-Cell Lymphomas

Human enteropathy-associated T-cell lymphoma (EATL) is classified into 2 distinct subgroups based on their phenotypes (type I and type II). Canine intestinal T-cell lymphoma can be morphologically classified into large and small cell lymphomas (LCL and SCL, respectively). Their association with human EATL or immunohistochemical and biological features has not been well characterized. In this study, the immunohistochemical profiles of 17 cases of LCL and 33 cases of SCL were evaluated with markers used for human EATL classification. Morphologically, LCL was characterized by sheet-like proliferation of large to moderately sized neoplastic lymphocytes, with scant clear cytoplasm and pleomorphic, irregularly shaped nuclei containing distinctive nucleoli and scattered chromatin. In contrast, SCL was characterized by the proliferation of monomorphic small neoplastic lymphocytes, accompanied by infiltration of nonneoplastic plasma cells. Interestingly, 8 cases demonstrated mixed LCL and SCL morphologies. Granular cytoplasmic expression of granzyme B was observed in most LCL and SCL cases. Membranous expression of CD56 was demonstrated in only 2 of 17 LCL and 0 of 33 SCL cases. Coexpression of CD20 by neoplastic T cells was observed in more SCL cases (16/33; 48%) than LCL cases (1/17; 6%). The CD56-positive cells in 2 cases were negative for CD20. Although canine LCL shares common features with human EATL type I, canine SCL cells and human EATL type II differ in their immunophenotype. Canine intestinal T-cell lymphoma had a homogeneous immunophenotype regardless of cell morphology. The findings of this study may indicate large cell transformation of SCL rather than 2 distinct entities.

Coexpression of CD3 and CD20 in Canine Enteropathy-Associated T-cell Lymphoma

The majority of primary intestinal lymphomas in dogs are T-cell lymphomas, with enteropathy-associated T-cell lymphoma (EATL) large cell type (type 1) being the most common. While most T-cell lymphomas express the T-cell marker CD3, there is increasing evidence that some human and canine T-cell lymphomas coexpress the B-cell marker CD20. We describe 3 cases of CD3+, CD20+, Pax5- EATL type 1 in dogs. All 3 cases had clonal rearrangement of T-cell receptor gamma. Initial clinical signs included weight loss, inappetence, diarrhea, and/or vomiting. The mean age was 9 years (range 3–12). Survival was highly variable ranging from 20 days to longer than 1.6 years. Considering the different chemotherapeutic response of T-cell versus B-cell lymphomas, accurate diagnosis of lymphomas coexpressing CD3 and CD20 as EATL type 1 based on histologic features and clonality results is important. Regardless, the clinical and/or prognostic significance of neoplastic T cells expressing CD20 is unclear.

There Are No Magic Bullets in Hematopathology: Even Immunostains for CD20 and CD3 Can Get You Into Trouble

Immunohistochemistry is a powerful tool for the diagnosis and subclassification of hematolymphoid neoplasms. However, the expression of certain markers is not always as expected, and unusual patterns of staining can lead to misdiagnosis. CD20 and CD3 are our most commonly used markers for identification of B cells and T cells, respectively, and they almost always yield reliable, specific staining. This discussion focuses on diagnostic pitfalls related to the use of immunohistochemistry for CD20 and CD3 in hematopathology, and specifically on diagnostic challenges that arise when (1) CD20 is not expressed in B-cell lymphomas, when (2) CD20 is expressed in plasma cell neoplasms and T-cell lymphomas, and when (3) CD3 is expressed in B-cell lymphomas and Hodgkin lymphoma.

Six Cases of CD20-Positive Adult T-Cell Leukemia

Adult T-cell leukaemia/lymphoma (ATLL) is a neoplasm originating in mature CD4⁺ peripheral T cells. However, rare cases of CD20⁺ ATLL have been reported. Here, we describe six cases of CD20⁺ ATLL diagnosed in our department. The median age was 79 years (range, 54-90 years); two patients were men, and four were women. Elevated lactate dehydrogenase was observed in four cases. All cases were lymphoma type and positive for human T-lymphotropic virus-1 (HTLV-1). HTLV-1 proviral DNA was detected in four cases. The Ann Arbor stage was I, II, or IV in one patient each and III in three patients. The clinical course was poor in almost all cases. Tumour cells were large in all cases, and flow cytometry revealed CD20⁺ lymphoma cells in five of six cases. Immunohistochemistry revealed lymphoma cells positive for CD20, CD3, CD4, and CCR4 and negative for CD8, CD79a, and PAX5 in all cases. CD20 expression was lower than that in normal B cells. One case was initially misdiagnosed as diffuse large B-cell lymphoma. Thus, combined use of an antibody panel and molecular genetic studies is important to avoid misdiagnosing ATLL as B-cell lymphoma.

Rituximab Downregulates Gene Expression Associated with Cell Proliferation, Survival, and Proteolysis in the Peripheral Blood from Rheumatoid Arthritis Patients: A Link between High Baseline Autophagy-Related ULK1 Expression and Improved Pain Control

Objective. To clarify molecular mechanisms for the response to rituximab in a longitudinal study. Methods. Peripheral blood from 16 RA patients treated with rituximab for a single treatment course and 26 healthy controls, blood and knee articular cartilages from 18 patients with long-standing RA, and cartilages from 14 healthy subjects were examined. Clinical response was assessed using ESR, ACPA, CRP, RF, DAS28 levels, CD19+ B-cell counts, bone erosion, and joint space narrowing scores. Protein expression in PBMCs was quantified using ELISA. Gene expression was performed with quantitative real-time PCR. Results. A decrease (p < 0.05) in DAS28, ESR, and CRP values after rituximab treatment was associated with the downregulation of MTOR, p21, caspase 3, ULK1, TNFα, IL-1β, and cathepsin K gene expression in the peripheral blood to levels found in healthy subjects. MMP-9 expression remained significantly higher compared to controls although decreased (p < 0.05) versus baseline. A negative correlation between baseline ULK1 gene expression and the number of tender joints at the end of follow-up was observed. Conclusions. The response to rituximab was associated with decreased MTOR, p21, caspase 3, ULK1, TNFα, IL-1β, and cathepsin K gene expression compared to healthy subjects. Residual increased expression in MMP-9, IFNα, and COX2 might account for remaining inflammation and pain. High baseline ULK1 gene expression indicates a good response in respect to pain.

CD20-positive primary gastric T-cell lymphoma poorly responding to initial treatment with rituximab plus CHOP, and a literature review

There have been rare reported cases of peripheral T-cell lymphoma, not otherwise specified (PTCL-NOS) that co-expressed CD20. A 44-year-old Japanese male was initially misdiagnosed as CD20-positive diffuse large B-cell lymphoma with a background of reactive CD3-positive T-cells in the stomach. After four cycles of R-CHOP [rituximab plus cyclophosphamide (CY), doxorubicin, vincristine, and prednisolone (PSL)], total gastrectomy with regional lymph node dissection was performed due to the poor response to R-CHOP. A final diagnosis of CD20-positive primary gastric PTCL-NOS was made based on the immunohistochemical, flow cytometric, and molecular genetic findings. In the present case, CD20 immunostaining for T-cell lymphoma cells in tumor tissue varied; in a large part, these were strong to weak-positive, and in some parts, absent. We additionally reviewed the literature focusing on CD20-positive PTCL-NOS treated with rituximab. The administration of rituximab has been performed as an initial treatment in 11 cases, including the case reported here. The response was good in cases with high expression of CD20, while it was poor in cases with variable intensity in CD20 staining, which is consistent with our experience in the present case. The efficacy of rituximab may be associated with intensity of CD20 expression in T cells and its homogeneity in the tumor tissue.

Activation of TLR2 and TLR6 by Dengue NS1 Protein and Its Implications in the Immunopathogenesis of Dengue Virus Infection

Dengue virus (DV) infection is the most prevalent mosquito-borne viral disease and its manifestation has been shown to be contributed in part by the host immune responses. In this study, pathogen recognition receptors, Toll-like receptor (TLR) 2 and TLR6 were found to be up-regulated in DV-infected human PBMC using immunofluorescence staining, flow cytometry and Western blot analyses. Using ELISA, IL-6 and TNF-α, cytokines downstream of TLR2 and TLR6 signaling pathways were also found to be up-regulated in DV-infected PBMC. IL-6 and TNF-α production by PBMC were reduced when TLR2 and TLR6 were blocked using TLR2 and TLR6 neutralizing antibodies during DV infection. These results suggested that signaling pathways of TLR2 and TLR6 were activated during DV infection and its activation contributed to IL-6 and TNF-α production. DV NS1 protein was found to significantly increase the production of IL-6 and TNF-α when added to PBMC. The amount of IL-6 and TNF-α stimulated by DV NS1 protein was reduced when TLR2 and TLR6 were blocked, suggesting that DV NS1 protein is the viral protein responsible for the activation of TLR2 and TLR6 during DV infection. Secreted alkaline phosphatase (SEAP) reporter assay was used to further confirm activation of TLR2 and TLR6 by DV NS1 protein. In addition, DV-infected and DV NS1 protein-treated TLR6^-/- mice have higher survivability compared to DV-infected and DV NS1 protein-treated wild-type mice. Hence, activation of TLR6 via DV NS1 protein could potentially play an important role in the immunopathogenesis of DV infection.

Despite the prevalence of dengue virus infection and the heavy economic burden it puts on the endemic countries, the immunopathogenesis of dengue virus infection remains unclear. Plasma leakage in dengue hemorrhagic fever (DHF) develops not when the viremia is at its peak in infected patients but when viremia has been significantly reduced or cleared. This suggests that host immune response is responsible for the development DHF. The interactions of the viral factors with host factors which trigger the host immune responses are likely to play a significant role in the development of dengue diseases, thus are of great interests. In this study, we found that dengue NS1 protein activates TLR2 and TLR6, leading to increase proinflammatory cytokine production. In addition, the interaction of viral factor with TLR6 was found to play an important role in the manifestation of dengue virus infection. Our study provides new insights into the involvement of TLR6 in dengue virus infection and the potential of using TLR6 anatagonist in therapeutic treatment for DV infection.

CD8-positive peripheral T-cell lymphoma with aberrant expression of CD20 and concurrent in situ follicular lymphoma

A case of a 78-year-old woman with a CD8-positive peripheral T-cell lymphoma with aberrant expression of CD20 associated with follicular lymphoma in situ (FLIS) is reported. The neoplasm presented initially as cutaneous macules, papules, plaques and nodules. A skin biopsy was performed and the diagnosis of peripheral T-cell lymphoma (PTCl) with aberrant expression of CD20 was made. The staging procedures included an excisional inguinal lymph node biopsy that showed findings similar to those of the previous diagnosis. In addition, FLIS was identified. The clinicopathologic features of PTCLs with aberrant CD20 expression involving the skin as well as this uncommon association are reviewed.

Acute and chronic B cell depletion disrupts CD4+ and CD8+ T cell homeostasis and expansion during acute viral infection in mice

B cells provide humoral protection against pathogens and promote cellular immunity through diverse nonclassical effector functions. To assess B cell function in promoting T cell homeostasis, mature B cells were either acutely or chronically depleted in mice using CD20 mAb. Acute B cell depletion in either 2- or 4-mo-old mice significantly reduced spleen and lymph node CD4(+) and CD8(+) T cell numbers, including naive, activated, and Foxp3(+)CD25(+)CD4(+) regulatory T cell subsets. The numbers of IFN-γ- and TNF-α-producing T cells were also significantly reduced. Chronic B cell depletion for 6 mo in aged naive mice resulted in a 40-70% reduction in activated CD4(+) and CD8(+) T cell numbers and 20-50% reductions in IFN-γ-producing T cells. Therefore, B cells were necessary for maintaining naive CD4(+) and CD8(+) T cell homeostasis for subsequent optimal T cell expansion in young and old mice. To determine the significance of this finding, a week of B cell depletion in 4-mo-old mice was followed by acute viral infection with lymphocytic choriomeningitis virus Armstrong. Despite their expansion, activated and cytokine-producing CD4(+) and CD8(+) T cell numbers were still significantly reduced 1 wk later. Moreover, viral peptide-specific CD4(+) and CD8(+) T cell numbers and effector cell development were significantly reduced in mice lacking B cells, whereas lymphocytic choriomeningitis virus titers were dramatically increased. Thus, T cell function is maintained in B cell-depleted mice, but B cells are required for optimal CD4(+) and CD8(+) T cell homeostasis, activation, and effector development in vivo, particularly during responses to acute viral infection.

Complement-dependent cytotoxicity crossmatch

The complement-dependent cytotoxic crossmatch is an informative test that detects alloantibodies in pre- and post-transplant patients, which may dictate clinical management of transplant patients. While challenging to perform, the cytotoxic crossmatch represents the only assay that provides direct evidence for the presence of potentially pathologic (i.e., cytotoxic) alloantibodies. The cytotoxic crossmatch combines patient (recipient) serum and donor cells. If donor-reactive alloantibodies are present in patient serum, these antibodies can bind donor cells. Antibody-antigen complexes, in turn, can activate the complement cascade, leading to complement-mediated cytotoxicity. Two commonly performed cytotoxic crossmatches, using donor lymphocytes as target cells, are described.

Peripheral T-Cell Lymphoma with Aberrant Expression of CD19, CD20, and CD79a: Case Report and Literature Review

A case of lymphoma of T-cell derivation with aberrant expression of three B-cell lineage markers (CD19, CD20, and CD79a), which was diagnosed on a left axillary excision, is described. Immunohistochemical studies and flow cytometry analysis demonstrated neoplastic cells expressing CD3, CD19, CD20, and CD79a with absence of CD4, CD8, CD10, CD30, CD34, CD56, CD68, TDT, MPO, PAX-5, and surface immunoglobulin. Gene rearrangement studies performed on paraffin blocks demonstrated monoclonal T-cell receptor gamma chain rearrangement with no evidence of clonal heavy chain rearrangement. The neoplastic cells were negative for Epstein-Barr virus (EBV) or Human Herpes Virus 8 (HHV-8). At the time of diagnosis, the PET scan demonstrated hypermetabolic neoplastic cells involving the left axilla, bilateral internal jugular areas, mediastinum, right hilum, bilateral lungs, and spleen. However, bone marrow biopsy performed for hemolytic anemia revealed normocellular bone marrow with trilineage maturation. The patient had no evidence of immunodeficiency or infection with EBV or HHV-8. This is the first reported case of a mature T-cell lymphoma with aberrant expression of three B-cell lineage markers. The current report also highlights the need for molecular gene rearrangement studies to determine the precise lineage of ambiguous neoplastic clones.

CD20-positive NK/T-cell lymphoma with indolent clinical course: report of case and review of literature

Abstract

CD20-positive T-cell lymphoma is extremely rare and only two cases of CD20-positive NK/T-cell lymphoma with aggressive clinical courses have been described in the literature. We present a case of unusual NK/T-cell lymphoma with CD20 expression in nasal cavity occurring in an elder female patient. The patient had presented with left nasal cavity nodule for 10 years. CT scan revealed a mass was located at the left anterior nasal cavity and was observed to extend into the ethmoid sinus. There was no regional lymph node involvement. Biopsy was performed and microscopical inspection revealed the lesion was composed of small- to middle-size atypical lymphoid cell, histiocytes, eosinophils, and neutrophils. The lymphoid cells were strongly immunoreactive to CD3, CD20, CD56, TIA-1 and granzyme-B. The Epstein-Barr virus genomes were also found in tumor cells by in situ hybridization. By genetic analysis, however, no clonal rearrangement of the T cell receptor-γ genes (TCRG), or the immunoglobulin heavy chain (IgH) gene was found. A diagnosis of CD20-positive extranodal NK/T-cell lymphoma, nasal type was made. The patient refused chemotherapy, and had been only on regular follow-up for 6 months. There was no sign of enlargement of tumor and extra-nasal dissemination by whole body positron emission tomography/computed tomography (PET/CT) study. The accurate diagnosis of NK/T-cell lymphoma with CD20 expression is important, but the indolent behavior of the present case is more unusual. A long-term follow-up is suggested to be performed to inspect the progression for this tumor.

Virtual slides

The virtual slides for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1320848277788495

CD20 Positive T Cell Lymphoma Involvement of Skin

CD20 positive T cell lymphoma is a rare condition that is associated with the coexpressions of CD20 and T cell markers, such as, CD3, CD5, or UCHL-1. Positivity for CD20 in this tumor represents an aberrant immunophenotype, but the presence of monoclonal T cell receptor (TCR) gene rearrangements and negativity for immunoglobulin heavy chain gene rearrangement indicate that this tumor is a T cell lymphoma. The majority of cases of CD20 positive T cell lymphoma have been reported as immature peripheral T cell lymphoma not otherwise specified. However, we believe that this disease is likely to be re-listed as a new disease entity after its pathogenesis has been elucidated and more cases have been evaluated. Here, we present a case of peripheral T cell lymphoma coexpressing CD20 and T cell markers with a demonstrable TCR gene rearrangement, in a patient who had been misdiagnosed as having B cell type lymphoma 4 years previously. We hypothesize that in this case initially circulating normal CD20+ T cell subsets underwent neoplastic transformation and CD20 positive T cell lymphoma subsequently developed in the lymph node, and then recurred in the skin due to systemic disease or metastasized from the nodal disease.

CD20-positive T-cell lymphoma with indolent clinical behaviour

T-cell lymphomas that are positive for CD20 are very rare and most reported cases have demonstrated an aggressive clinical course. An unusual case of a 57-year old female who presented with recurrent enlarged lymph nodes for 12 years is reported. The lymph nodes from both 1995 and 2007 showed effacement of the lymph node architecture by a diffuse and dense infiltrate of small lymphoid cells. In terms of T- and B-cell markers, these small lymphoid cells were immunohistochemically positive for CD2, CD3, CD5, CD43, CD45RO and CD20, and were negative for PAX5, CD79a and cyclin D1. Molecular genetic analysis showed T-cell receptor-gamma chain gene rearrangement. Recognition of this type of CD20-positive T-cell lymphoma is important for ensuring a correct diagnosis so that the patient can be offered the most appropriate therapy. The indolent behaviour of the present case is unusual and awaits further clinical follow-up and laboratory investigation.

PAX5-positive T-cell anaplastic large cell lymphomas associated with extra copies of the PAX5 gene locus

Cell lineage is the major criterion by which lymphomas are classified. Immunohistochemistry has greatly facilitated lymphoma diagnosis by detecting expression of lineage-associated antigens. However, loss or aberrant expression of these antigens may present diagnostic challenges. Anaplastic large cell lymphoma is a T-cell lymphoma that shows morphologic and phenotypic overlap with classical Hodgkin's lymphoma, which is a tumor of B-cell derivation. Staining for the B-cell transcription factor, paired box 5 (PAX5), has been suggested to be helpful in this differential, as it is positive in most classical Hodgkin's lymphomas, but absent in anaplastic large cell lymphomas. In this study we report four systemic T-cell anaplastic large cell lymphomas that were positive for PAX5 by immunohistochemistry, with weak staining intensity similar to that observed in classical Hodgkin's lymphoma. All diagnoses were confirmed by a combination of morphologic, phenotypic, and molecular criteria. Three cases were anaplastic lymphoma kinase (ALK) negative and one was ALK positive. PAX5 immunohistochemistry was negative in 198 additional peripheral T-cell lymphomas, including 66 anaplastic large cell lymphomas. Unexpectedly, although PAX5 translocations were absent, all evaluable PAX5-positive anaplastic large cell lymphomas showed extra copies of the PAX5 gene locus by fluorescence in situ hybridization (FISH). In contrast, only 4% of PAX5-negative peripheral T-cell lymphomas had extra copies of PAX5. We conclude that aberrant expression of PAX5 occurs rarely in T-cell anaplastic large cell lymphomas, and may be associated with extra copies of the PAX5 gene. PAX5-positive lymphomas with morphologic features overlapping different lymphoma types should be evaluated with an extensive immunohistochemical panel and/or molecular studies to avoid diagnostic errors that could lead to inappropriate treatment. As PAX5 overexpression causes T-cell neoplasms in experimental models, PAX5 may have contributed to lymphomagenesis in our cases.

Immunocytochemistry and the diagnosis of cutaneous lymphoma

Cutaneous lymphoid infiltrates may pose some of the most difficult diagnostic problems in dermatopathology. Immunocytochemistry is often employed in an effort to determine whether an infiltrate is neoplastic or, in the case of clearly malignant infiltrates, to provide a specific diagnosis. The rarity of these disorders and the variant immunocytochemical profiles they may present further thwart understanding and sometimes prevent an accurate diagnosis. In this review the common immunocytochemical profiles of various cutaneous lymphomas are presented and potential pitfalls and problems considered. Immunocytochemistry is not a diagnostic test but, as in other areas of histopathology, is a highly valuable tool that requires critical interpretation within a context: so applied, it is an indispensable part of the pathologist's arsenal in evaluating lymphoid infiltrates and defining different lymphomas.

Translational Mini-Review Series on B Cell-Directed Therapies: Recent advances in B cell-directed biological therapies for autoimmune disorders

B cell-directed therapies are promising treatments for autoimmune disorders. Besides targeting CD20, newer B cell-directed therapies are in development that target other B cell surface molecules and differentiation factors. An increasing number of B cell-directed therapies are in development for the treatment of autoimmune disorders. Like rituximab, which is approved as a treatment for rheumatoid arthritis (RA), many of these newer agents deplete B cells or target pathways essential for B cell development and function; however, many questions remain about their optimal use in the clinic and about the role of B cells in disease pathogenesis. Other therapies besides rituximab that target CD20 are the furthest along in development. Besides targeting CD20, the newer B cell-directed therapies target CD22, CD19, CD40-CD40L, B cell activating factor belonging to the TNF family (BAFF) and A proliferation-inducing ligand (APRIL). Rituximab is being tested in an ever-increasing number of autoimmune disorders and clinical studies of rituximab combined with other biological therapies are being pursued for the treatment of rheumatoid arthritis (RA). B cell-directed therapies are being tested in clinical trials for a variety of autoimmune disorders including RA, systemic lupus erythematosus (SLE), Sjögren's syndrome, vasculitis, multiple sclerosis (MS), Graves' disease, idiopathic thrombocytopenia (ITP), the inflammatory myopathies (dermatomyositis and polymyositis) and the blistering skin diseases pemphigus and bullous pemphigoid. Despite the plethora of clinical studies related to B cell-directed therapies and wealth of new information from these trials, much still remains to be discovered about the pathophysiological role of B cells in autoimmune disorders.

Primary cutaneous peripheral T-cell lymphoma with aberrant coexpression of CD20: case report and review of the literature

We report an unusual case of primary cutaneous T-cell lymphoma in a 45-year-old male showing expression of the B-cell marker CD20. The lesion presented as a large plaque on the right shin and rapidly developed into additional lesions on the right lower leg and right anterior chest. Despite therapy, bone involvement was discovered at 1 year after initial presentation. Punch biopsy of the right leg revealed a diffuse, atypical dermal lymphocytic infiltrate with papillary edema and no epidermotropism. The atypical cells strongly expressed the T-cell markers CD3, CD2, and CD43, with additional expression of cytotoxic T-cell markers CD8, cytotoxic granule-associated RNA binding protein (TIA-1), and granzyme B and loss of CD7 by immunohistochemistry (IHC). In addition, the atypical cells with the above phenotype exhibited moderate expression of CD20 by IHC. Coexpression of CD8 and CD20 in the atypical cells was confirmed by a dual-labeled IHC stain. Clonal rearrangements of the T-cell receptor gamma- and beta-chain genes were detected by polymerase chain reaction; however, there was no expression of T-cell receptor beta-chain identified by IHC. In conclusion, we present a case a of CD8-positive primary cutaneous T-cell lymphoma with CD20 expression, exhibiting aggressive behavior.

Best practices in contemporary diagnostic immunohistochemistry: panel approach to hematolymphoid proliferations

CONTEXT

The complexities of diagnostic hematopathology in the modern era are well known, and even in this molecular era, immunophenotypic studies, together with routine histopathology, remain a critical component in the evaluation of many lymphoid proliferations. With numerous antibodies that can be used on routinely fixed, paraffin-embedded tissue sections, immunohistochemistry has become increasingly valuable. It then becomes a challenge knowing the best approach to the selection of antibodies to use and how to interpret them.

OBJECTIVE

To present a pragmatic immunohistochemical approach to the evaluation of lymphoid proliferations that stresses the utility of 2 limited panels to deal with the most commonly encountered lymphomas.

DATA SOURCES

English-language literature published between 1990 and 2008.

CONCLUSIONS

A relatively limited panel of immunohistochemical stains may be used to diagnose and subclassify many of the more common lymphomas, although some cases will require additional stains and others fewer, depending on the case complexity. Immunohistochemical stains must always be interpreted in the context of the histopathologic and other ancillary studies.

Rare lymphoid neoplasms coexpressing B- and T-cell antigens. The role of PAX-5 gene methylation in their pathogenesis

We report 3 cases of lymphoid neoplasms with mixed lineage features of T-, NK-, or B-cell marker expression and clonal gene rearrangement for both T-cell receptor and immunoglobulin light chain IgK. A characteristic of our cases was the lack of expression of the specific B-cell transcription factor, Pax5, which is essential for maintaining the identity and function of mature B cells during late B lymphopoiesis. In the absence of Pax5, B cells in vitro can differentiate into macrophages, dendritic cells, granulocytes, and T/NK cells. Methylation analysis of the Pax5 gene in our cases suggests that its inactivation by this epigenetic event in a committed or mature B cell, before plasma cell differentiation, may well be a common pathogenetic mechanism in mature lymphoid neoplasms with expression of multilineage antigens. In particular, case 1 may represent a mixed NK- and B-cell lineage; and cases 2 and 3 may represent mixed T and B-cell lineage, respectively. Aberrations in the DNA methylation patterns are currently recognized as a hallmark of human cancer. Cases with aberrant phenotypes require molecular analysis for lineage assignment. Studies of such cases may be helpful to better elucidate whether they represent a distinct entity with clinical, immunophenotypic, and molecular characteristics or an incidental phenomenon during malignant transformation. Interestingly, these cases were all characterized by poor clinical outcome.

CD3-positive large B-cell lymphoma

It is not uncommon for some B-lineage non-Hodgkin lymphomas (NHLs) to aberrantly coexpress T-cell markers, particularly CD5, as well as CD7, CD2, CD4, and/or CD8 in rare cases. Cases of CD3-positive B-cell NHL, however, have not previously been described in the literature. We present 4 cases of large B-cell lymphoma aberrantly coexpressing T-cell marker CD3 and B-lineage markers as well as demonstrating clonal rearrangement of the immunoglobulin genes but not the gamma T-cell receptor gene. To our knowledge, this represents the first series report of B-cell NHL coexpressing T-lineage-specific marker CD3. The identification of such cases indicates that the use of CD3 antibody alone in paraffin sections may lead to an incorrect determination of cell lineage in some B-cell NHL. Immunohistochemistry using additional cell lineage specific markers or molecular analysis for antigen receptor gene rearrangements are necessary for correct determination of the cell lineage in such cases.

Novel CD19 expression in a peripheral T cell lymphoma: A flow cytometry case report with morphologic correlation

BACKGROUND

Peripheral T-cell lymphomas are uncommon lymphomas that show T-cell antigenic loss and clonal T-cell receptor (TCR) gene rearrangement. Rare cases of T-cell lymphomas with aberrant expression of CD20 have been described. However, CD19 coexpression in a mature T-cell neoplasm has not been reported.

METHODS

Histology, immunohistochemistry (IHC), and PCR for TCR gene rearrangement were performed on an excised lymph node specimen and a subsequent fine needle aspiration (FNA) of an additional lymph node. Flow cytometry (FC) was performed on FNA and peripheral blood specimen.

RESULTS

The lymph node's architecture was effaced by a diffuse atypical lymphoid proliferation that, by IHC, was positive for CD3, CD2, and CD43 and negative for CD4, CD5, CD8, TdT, CD1a, and B-cell-associated antigens PAX-5, CD20, and CD79a. A clonal TCR gene rearrangement was detected. FC was performed on a subsequent FNA, and peripheral blood specimen demonstrated an aberrant T-cell population with expression of CD2, CD3, CD27, TCR alpha/beta, CD52, CD38, CD45, and CD26 (partial expression) and negative for CD4, CD5, CD7, CD8, CD10, CD30, and CD56. The aberrant T-cell population also expressed bright CD19.

CONCLUSIONS

Using FC, we describe the first case of peripheral T-cell lymphoma with aberrant coexpression of CD19.