CD123-Positive Plasmacytoid Dendritic Cells in Primary Cutaneous Marginal Zone B-Cell Lymphoma: A Crucial Role and a New Lymphoma Paradigm

Cutaneous Pseudolymphoma With Langerhans Cell Hyperplasia-A Rare Case With Clinical Presentation Mimicking Malignancy and Potential Diagnostic Pitfall

ABSTRACT

We describe a rare case of cutaneous pseudolymphoma with Langerhans cell hyperplasia. An 84-year-old female patient presented with erythematous and pernicious-looking plaques on her scalp that had been present for months. Histologically, lymphoid follicles consisting of mixed-type lymphocytes and Langerhans cells were aggregated focally. The diagnosis was verified by several immunohistochemical stains and by clinical evaluation. Skin lesions were steadily resolved with low-dose corticosteroid and hydroxychloroquine.

Dermatological Considerations in the Diagnosis and Treatment of Marginal Zone Lymphomas

Primary cutaneous marginal zone lymphoma (PC-MZL) is a B-cell lymphoma arising in the skin. Although it is a rare disease, PC-MZL accounts for 20-40% of all primary cutaneous B-cell lymphoma in Western Countries. The aetiology and the pathogenesis of PC-MZL are poorly understood, as it generally lacks the chromosomal translocations most typically present in marginal zone lymphomas of other sites. The diagnosis of PC-MZL may be challenging, due to the rarity of the disease, and needs the competence of different professional figures, including the dermatologist and the pathologist. Furthermore, the management of the patient after the diagnosis is complex and involves the dermatologist, the haematologist, the surgeon, the radiotherapist and the radiologist. The aim of this review is to describe the clinical and histological findings for the diagnosis of PC-MZL, and the state of art for the management of the patient.

Diagnostic utility of plasmacytoid dendritic cells in dermatopathology

Differentiating cutaneous diseases that mimic each other clinically and histopathologically can at times be a challenging task for the dermatopathologist. At the same time, differentiation of entities with overlapping features may be crucial for patient management. Although not seen in normal skin, plasmacytoid dendritic cells usually infiltrate the skin in several infectious, inflammatory/autoimmune and neoplastic entities. Plasmacytoid dendritic cells can be identified in tissue using specific markers such as CD123 and/or blood-derived dendritic cell antigen-2. Plasmacytoid dendritic cells are the most potent producers of type I interferons and their activity may therefore be assessed indirectly in tissue using human myxovirus resistance protein A, a surrogate marker for type I interferon production. In recent years, accumulating evidence has established the utility of evaluating for specific plasmacytoid dendritic cell-related parameters (plasmacytoid dendritic cell content, distribution and clustering and/ or human myxovirus resistance protein A expression) as a diagnostic tool in differentiating cutaneous diseases with overlapping features such as the alopecias, lupus and its mimics, and neoplastic entities. In this review, we provide an update on the current evidence on this topic and on the contexts where this can be a useful adjunct to reach the histopathological diagnosis.

A Systematic Approach to the Cutaneous Lymphoid Infiltrates: A Clinical, Morphologic, and Immunophenotypic Evaluation

CONTEXT.—

The evaluation of cutaneous lymphoid infiltrates, both neoplastic and inflammatory, occurs very frequently in routine dermatopathologic examination and consultation practices. The "tough" cutaneous lymphoid infiltrate is feared by many pathologists; skin biopsies are relatively small, whereas diagnostic possibilities are relatively broad. It is true that cutaneous lymphomas can be difficult to diagnose and that in many circumstances multiple biopsies are required to establish a correct diagnostic interpretation. As a reminder, one should understand that low-grade cutaneous lymphomas are indolent disorders that usually linger for decades and that therapy does not result in disease cure. It is also important to remember that in most circumstances, those patients will die from another process that is completely unrelated to a diagnosis of skin lymphoma (even in the absence of specific therapy).

OBJECTIVE.—

To use a clinicopathologic, immunophenotypic, and molecular approach in the evaluation of common lymphocytic infiltrates.

DATA SOURCES.—

An in-depth analysis of updated literature in the field of cutaneous lymphomas was done, with particular emphasis on updated terminology from the most recent World Health Organization classification of skin and hematologic tumors.

CONCLUSIONS.—

A diagnosis of cutaneous lymphoid infiltrates can be adequately approached using a systematic scheme following the proposed ABCDE system. Overall, cutaneous T- and B-cell lymphomas are rare and "reactive" infiltrates are more common. Evaluation of lymphoid proliferations should start with a good sense of knowledge of the clinical presentation of the lesions, the clinical differential considerations, and a conscientious and appropriate use of immunohistochemistry and molecular tools.

cDC2 and plasmacytoid dendritic cells diminish from tissues of patients with non-Hodgkin orbital lymphoma and idiopathic orbital inflammation

Non-Hodgkin orbital lymphoma (NHOL) and idiopathic orbital inflammation (IOI) are common orbital conditions with largely unknown pathophysiology. To investigate the immune cell composition of these diseases, we performed standardized 29 parameter flow cytometry phenotyping in peripheral blood mononuclear cells of 18 NHOL patients, 21 IOI patients, and 41 unaffected controls. Automatic gating by FlowSOM revealed decreased abundance of meta-clusters containing dendritic cells in patients, which we confirmed by manual gating. A decreased percentage of (HLA-DR⁺ CD303⁺ CD123⁺ ) plasmacytoid dendritic cells (pDC) in the circulation of IOI patients and decreased (HLA-DR⁺ CD11c⁺ CD1c⁺ ) conventional dendritic cells (cDC) type-2 for IOI patients were replicated in an independent cohort of patients and controls. Meta-analysis of both cohorts demonstrated that pDCs are also decreased in blood of NHOL patients and highlighted that the decrease in blood cDC type-2 was specific for IOI patients compared to NHOL or controls. Deconvolution-based estimation of immune cells in transcriptomic data of 48 orbital biopsies revealed a decrease in the abundance of pDC and cDC populations within the orbital microenvironment of IOI patients. Collectively, these data suggest a previously underappreciated role for dendritic cells in orbital disorders.

Plasmacytoid dendritic cells in granulomatous variant of mycosis fungoides

INTRODUCTION

Granulomatous mycosis fungoides (MF) is a rare variant in which granulomas are associated with other typical signs of MF. Its prognosis is worse than that of classical MF. Plasmacytoid dendritic cells (PDCs) are a subset of interferon-producing dendritic cells that link the innate and the adaptative immune responses. They have also been related to tolerance to certain tumors such as melanoma.

MATERIALS AND METHODS

In this article, we examined for the presence of CD123+ PDC in six cases of granulomatous MF from our archives.

RESULTS

We found clusters of 10 or more positive cells in three of six cases of granulomatous MF (two women and a man, in their sixth and seventh decade). Although in two of these three cases the granulomatous response was extensive, in the other, it only represented 10% of the infiltrate of the biopsy. In all three cases, the granulomas were epithelioid, sarcoidal type.

CONCLUSIONS

CD123+ PDC can be identified in granulomatous MF. The pathogenic and prognostic role of this finding requires further clarification.

Lymphoma or pseudolymphoma: A report of six cases and review of the literature

To explore and compare the clinical presentations and pathologic features of cutaneous pseudolymphomas (CPL) with primary cutaneous lymphomas. Review literature in order to improve the treatment of CPL. Six cases of CPLs were collected. The clinical, pathologic, and immunohistochemical features were performed and analyzed in Peking Union Medical College Hospital in 2018. Of six patients, the distributions and clinical manifestations of skin lesions are varied. The pathologic features consisted of atypical prominent lymphocytes infiltration. Of them, two cases imitated mycosis fungoides, one case mimicked primary cutaneous aggressive pidermotropic CD8+ cytotoxic T-cell lymphoma, one case was diagnosed as Jessner-Kanof lymphocyte infiltration and two cases primary cutaneous CD4+ small/medium T-cell lymphoproliferative disorder. With respect to etiology, one was result from insects bite and the others were on account of drugs. All cases were treated with systemic or local glucocorticoid. The skin lesions and systemic symptoms showed notable improvement after treatment. Follow-up visits were 2 years, half a year, and months, respectively, without relapse. These unique types of CPL were similar to cutaneous lymphomas in clinical manifestation and pathology. They were all sensitive to the treatment of externally or orally using glucocorticoid. The prognosis is generally good but needs long-term follow-up.

Cutaneous Pseudolymphoma

The term, cutaneous pseudolymphoma (PSL), refers to a group of lymphocyte-rich infiltrates, which either clinically and/or histologically simulate cutaneous lymphomas. Clinicopathologic correlation is essential to achieve the final diagnosis in cutaneous PSL and to differentiate it from cutaneous lymphomas. A wide range of causative agents (eg, Borrelia, injections, tattoo, and arthropod bite) has been described. Based on clinical and/or histologic presentation, 4 main groups of cutaneous PSL can be distinguished: (1) nodular PSL, (2) pseudo-mycosis fungoides, (3) other PSLs (representing distinct clinical entities), and (4) intravascular PSL. The article gives an overview of the clinical and histologic characteristics of cutaneous PSLs.

Plasmacytoid dendritic cell role in cutaneous malignancies

Plasmacytoid dendritic cells (pDCs) correspond to a specialized dendritic cell population that exhibit plasma cell morphology, express CD4, CD123, HLA-DR, blood-derived dendritic cell antigen-2 (BDCA-2), and Toll-like receptor (TLR)7 and TLR9 within endosomal compartments. Through their production of type I interferons (IFNs) and other pro-inflammatory cytokines, pDCs provide anti-viral resistance and link the innate and adaptive immunity by controlling the function of myeloid DCs, lymphocytes, and natural killer (NK) cells. While lacking from normal skin, pDCs are usually recruited to the skin in several cutaneous pathologies where they appear to be involved in the pathogenesis of several infectious, inflammatory/autoimmune, and neoplastic entities. Among the latter group, pDCs have the potential to induce anti-tumour immunity; however, the complex interaction of pDCs with tumor cells and their micro-environment appears to contribute to immunologic tolerance. In this review, we aim at highlighting the role played by pDCs in cutaneous malignancies with special emphasis on the underlying mechanisms.

Characterization of the tumor microenvironment in primary cutaneous CD30-positive lymphoproliferative disorders: a predominance of CD163-positive M2 macrophages

BACKGROUND

The tumor microenvironment is essential for tumor survival, growth and progression. There are only a few studies on the tumor microenvironment in cutaneous CD30-positive lymphoproliferative disorders.

METHODS

We assessed the composition of the tumor microenvironment using immunohistochemistry studies in skin biopsies from cases diagnosed with lymphomatoid papulosis (LyP: 18 specimens), primary cutaneous anaplastic large-cell lymphoma (PC-ALCL: 8 specimens), and reactive diseases harboring CD30-positive cells (18 specimens).

RESULTS

The predominant cells present in LyP and PC-ALCL were CD163+ M2 macrophages (44.7%, 35%), followed by CD8+ tumor infiltrating lymphocytes (11%, 15%), FOXP3+ T-regulatory cells (9%, 4.5%) and programmed cell death 1(PD-1) + lymphocytes (2.2%, 6.8%). In contrast, CD30-positive reactive inflammatory and infectious disorders were characterized by higher numbers of CD123+ plasmacytoid dendritic cells (6.3%) when compared to LyP (1%), and PC-ALCL (1.1%).

CONCLUSIONS

Key differences exist between the microenvironment of CD30-positive lymphoproliferative disorders and reactive conditions harboring CD30-positive lymphocytes. The high number of tumor associated macrophages, and the close vicinity of these immune cells to the CD30-positive tumor cells might suggest that tumor associated macrophages have direct influence on tumorigenesis in LyP and ALCL. Therefore, modulation of M2 macrophages may represent a new therapeutic strategy in cutaneous CD30-positive lymphoproliferative disorders.

Cutaneous lymphomas: an update. Part 2: B-cell lymphomas and related conditions

: Primary cutaneous B-cell lymphomas (PCBCL) are the second most common form of primary cutaneous lymphomas and account for approximately 25%-30% of all primary cutaneous lymphomas. Both forms of low-grade malignant PCBCL, primary cutaneous follicle center lymphoma (PCFCL) and primary cutaneous marginal zone lymphoma of mucosa-associated lymphoid tissue-type (MALT lymphoma) (PCMZL) represent the vast majority of PCBCL and show an indolent slowly progressive course and an excellent prognosis despite a high recurrence rate. Genetic analysis indicates that PCMZL differ from other forms of extranodal MALT lymphomas. The more common class-switched and the non-class-switched form of PCMZL can be distinguished as two distinctive subsets that differ in the cellular composition, IgM expression, and biological behavior with extracutaneous involvement found in the non-class-switched form. Recently, unusual clinical and histological forms of PCMZL and PCFCL manifesting with miliary or agminated lesions have been described that are diagnostically challenging. In contrast to PCMZL and PCFCL, primary cutaneous diffuse large B-cell lymphoma, leg type, and other rare forms of large B-cell lymphomas such as intravascular large B-cell lymphoma have an unfavorable prognosis. There is an emerging group of Epstein-Barr virus (EBV)-driven B-cell lymphoproliferations including posttransplant lymphoproliferative disorders and mucocutaneous ulcer occurring in immunocompromised patients and EBV-associated diffuse large B-cell lymphoma of the elderly arising in the setting of senescence-linked immunodeficiency. This review reports on recent findings expanding the spectrum of clinicopathological features, differential diagnostic aspects, and the pathogenesis of PCBCL and discusses the group of EBV-associated B-cell lymphoproliferations involving the skin.

Primary cutaneous marginal zone lymphoma with sequential development of nodal marginal zone lymphoma in a patient with selective immunoglobulin A deficiency

Multiple lymphoma subtypes occurring within one patient is rare in the context of B-cell lymphoma, and only few such cases have been reported in association with primary cutaneous marginal zone lymphoma (PCMZL). We herein describe the case of a 43-year-old patient who was diagnosed with PCMZL and subsequently developed a clonally unrelated nodal marginal zone lymphoma (MZL). At the time of diagnosis of PCMZL, multiple skin lesions were present. The atypical lymphoid infiltrate showed monotypic expression of immunoglobulin light chain lambda and heavy chain (IgM) on immunohistochemistry and an identical B-cell clone. No sign of systemic lymphoma was present in staging examinations. Complete remission was achieved utilizing rituximab. After a 3-year clinical course of repetitive cutaneous relapses and remissions, the patient additionally developed nodal lymphoma involvement by MZL which, however, harbored an immunophenotype and a genetic clone distinct from the cutaneous lymphoma counterpart. Therefore, the rare occurrence of two different types of MZL with sequential evolution was diagnosed. In this uncommon case, we hypothesize that selective immunoglobulin A deficiency may play a promoting role for the metachronous development of the two MZL that occurred in our patient.

Comments on cutaneous lymphomas: since the WHO-2008 classification to present

The last classification of lymphomas of the World Health Organization in 2008 made a few changes from the preceding classification. Although useful, at the same time, it has posed new questions, concerns, and dilemmas which have been raised in the literature. The current report highlights some of these controversies, of each of these primary cutaneous entities, going through cutaneous mature T-cell and NK-cell neoplasms, mature B-cell neoplasms, precursor neoplasms, and other entities, which for several reasons do not fit in the previous categories. It also reviews some advances on many of these lymphomas published in the last 2 years.