CD20 positive mycosis fungoides: a case report

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.

Primary Cutaneous Anaplastic Large-Cell Lymphoma With Aberrant CD20 Expression: Case Report and Review of the Literature

ABSTRACT

Cutaneous CD20 + T-cell lymphomas are exceedingly rare. Differentiating cases of T-cell lymphoma with aberrant expression of the B-cell marker CD20 from B-cell lymphoma may be associated with misdiagnosis or delays in diagnosis. We report, to the authors' knowledge, the first case of CD20 + primary cutaneous anaplastic large-cell lymphoma and review the literature to characterize published cases of CD20 + cutaneous T-cell lymphoma (n = 40). There is no accepted explanation for this phenomenon; however, it is suspected that these cases may be due to neoplastic transformation of CD20 + T cells or that CD20 may represent a T-cell activation marker. Expression of CD20 may have clinical significance in prognostication and consideration of treatment options with anti-CD20 therapies such as rituximab.

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.

Multispectral Imaging Approach to the Diagnosis of a CD20+ Cutaneous T-cell Lymphoproliferative Disorder: A Case Report

Expression of the pan B-cell marker CD20 by T-cell lymphoproliferative disorders is exceedingly rare. We present a 52-year-old man with a unilesional cutaneous CD20 T-cell lymphoproliferative disorder. Multispectral imaging analysis of CD3-CD20 double-stained lesional tissue sections allowed (1) the visualization of double-positive T lymphocytes in situ with sensitivity superior to that of conventional immunohistochemistry and (2) the quantitative assessment of marker coexpression. Here, 23% of CD3 signals in the patient's lesion were also CD20, whereas 38% of CD20 signals were also CD3. In contrast, both parameters were below 1% in the tonsil control. Overall, the percentage of double-positive cells in lesional skin was 35%, although only 0.4% of such cells were detected in the tonsil. This is the first demonstration of aberrant CD20 expression by skin-infiltrating T cells using multispectral imaging.

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.

Primary cutaneous T-cell lymphoma presenting as mycosis fungoides with a T-/null-cell phenotype: report of two cases

Variations in the clinical and histological presentation of cutaneous T-cell lymphoma (CTCL) can hamper diagnosis. We report two cases of a novel presentation of CTCL characterized by an aberrant immunophenotype with complete loss of pan T-cell antigens including T-cell receptor β chain and showing the clinical and histopathological appearance of erythrodermic and plaque-stage mycosis fungoides.

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.

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.

CD20-positive T-cell large granular lymphocyte leukemia: case report and review of the literature

CD20-positive T-cell malignancy is a rare disease. We report a case of CD20-positive T-cell large granular lymphocyte leukemia (T-LGLL). The leukemic cells were positive for CD20 and T cell markers, such as CD3, CD4, CD5, CD8 and CD57. A monoclonal rearrangement of the T-cell receptor (TCR) beta chain gene was detected. Twenty-three cases of well-documented CD20-positive T-cell malignancies were reviewed. Most cases were mature T-cell malignancies, especially exhibiting a cytotoxic T-cell phenotype, despite a diversity of the pathological diagnoses. Additional cases must be evaluated to clarify the implications of CD20 expression on T-cell malignancies and to elucidate whether such cases constitute a distinct biologic and clinical disease entity. The accumulation of cases will help to facilitate provision of a proper treatment for CD20-positive T-cell malignancies in the future.