Primary cutaneous marginal zone lymphomas with plasmacytic differentiation show frequent IgG4 expression

Cutaneous lymphoproliferative disorders: Back to the future

In the 1980s, immunohistochemistry and clonality analyses became instrumental in the recognition and definition of new types of cutaneous T-cell lymphoma (CTCL) and cutaneous B-cell lymphoma (CBCL) and the development of new classifications. By accepting loss of pan-T-cell antigens and clonal T-cell receptor gene rearrangements as important criteria to differentiate between benign and malignant T-cell proliferations, and monotypic immunoglobulin light-chain expression and clonal immunoglobulin gene rearrangements as crucial criteria to distinguish between benign and malignant B-cell proliferations, many cases, until then diagnosed as cutaneous lymphoid hyperplasia or pseudolymphoma, were reclassified as primary cutaneous CD4+ small/medium T-cell lymphoma (PCSM-TCL) or primary cutaneous marginal zone lymphoma (PCMZL), respectively. However, in recent years there is growing awareness that neither these immunohistochemical criteria nor demonstration of T-cell or B-cell clonality is specific for malignant lymphomas. In addition, many studies have reported that these low-grade malignant CTCL and CBCL have an indolent clinical behavior and an excellent prognosis with disease-specific survival rates of or close to 100%. As a result, recent classifications have downgraded several low-grade malignant cutaneous lymphomas to lymphoproliferative disorder (LPD). Both the 5th edition of the WHO classification (2022) and the 2022 International Consensus Classification (ICC) of mature lymphoid neoplasms reclassified PCSM-TCL as primary cutaneous CD4+ small/medium T-cell LPD and primary cutaneous acral CD8+ T-cell lymphoma as primary cutaneous acral CD8+ T cell LPD. While the 2022 ICC introduced the term "primary cutaneous marginal zone LPD," in the 5th edition of the WHO classification PCMZL is maintained. In this review we describe the background and rationale of the continually changing terminology of these conditions and discuss the clinical consequences of downgrading malignant lymphomas to LPDs.

New classifications of B-cell neoplasms: a comparison of 5th WHO and International Consensus classifications

In 2024, the World Health Organization (WHO) launched a new classification of lymphoid neoplasms, a revision of the previously used Revised 4th Edition of their classification (WHO-4R). However, this means that two classifications are now in simultaneous use: the 5th Edition of the WHO classification (WHO-5) and the International Consensus Classification (ICC). Instead of a comprehensive review of each disease entity, as already described elsewhere, this review focuses on revisions made in both the WHO-5 and ICC from WHO-4R and discrepancies between them regarding B-cell neoplasms. Similarities include cutaneous marginal zone lymphoma, cold agglutinin disease, non-primary effusion lymphoma-type effusion-based lymphoma, and gray zone lymphoma. Differences include plasma cell neoplasms, high-grade B-cell lymphoma (double hit lymphoma), follicular lymphoma, LPD with immune deficiency and dysregulation, extranodal large B-cell lymphoma, transformations of indolent B-cell lymphomas, and diffuse large B-cell lymphoma, not otherwise specified. Understanding the similarities and differences between the two latest classifications will aid daily diagnostic practice and future research on lymphoid neoplasms.

Primary localized cutaneous lichen myxedematosus with light chain-restricted plasma cells: A distinct variant of the localized form of lichen myxedematosus

Lichen myxedematosus (LM) is a chronic cutaneous mucinosis that can present as a localized skin lesion or as a generalized systemic disease termed scleromyxedema. The differential diagnosis is determined by a combination of clinical presentation, serological studies, and histopathological examination. Currently, well-established and accepted histopathological features to distinguish localized LM from scleromyxedema have not been elucidated. Our recent publication, together with a retrospective literature review, suggests that the presence of groups of light chain-restricted plasma cells represents a distinct histopathological clue for the diagnosis of localized LM. In this report, we provide two additional cases of localized LM with lambda light chain-restricted plasma cells, together with clinical and histopathological findings that are similar to our previous publication. These cases support our theory that the light chain-restricted plasmacytic microenvironment is primarily attributed to the pathogenesis of localized LM. Therefore, we consider these cases to constitute a clinically and pathologically new variant of localized LM and name it primary localized cutaneous LM with light chain-restricted plasma cells.

IgG4-related lymphadenopathy

IgG4-related lymphadenopathy is a nodal manifestation of IgG4-related disease (IgG4RD) which is characterized by increased polytypic IgG4+ plasma cells and IgG4+/IgG+ plasma cell ratio in lymph nodes and morphologically manifested as various patterns of reactive lymphadenopathy: Castleman disease-like, follicular hyperplasia, interfollicular expansion, progressive transformation of germinal centers and inflammatory pseudotumor-like. It typically presents with solitary or multiple, mild to moderate lymph node enlargement in otherwise asymptomatic patients. The serum IgG4 level is frequently elevated but C-reactive protein often remains normal. In patients not having a history of IgG4RD or manifestation of extranodal IgG4RD, a diagnosis of IgG4-lymphadenopathy should only be made with great caution given the non-specific morphologic features that can overlap with ANCA-associated vasculitis, interleukin-6 syndromes, Rosai-Dorfman disease, inflammatory myofibroblastic tumor, syphilis, lymphoma, and plasma cell neoplasia. Elevated IgG4 parameters, appropriate morphologies, and clinical correlation are essential to make the diagnosis of IgG4-lymphadenopathy more specific and clinically meaningful.

Primary cutaneous marginal zone lymphoproliferative disorder following COVID-19 vaccination

During the coronavirus disease 2019 (COVID-19) pandemic, COVID-19 vaccines were administered worldwide. A number of skin reactions, including primary cutaneous T-cell lymphoproliferative disorders (LPDs) were reported following COVID-19 vaccination. We report a case of primary cutaneous marginal zone lymphoproliferative disorder (PCMZLPD) secondary to COVID-19 vaccination. A 57-year-old man presented with an erythematous nodule on his left arm at the site of vaccine inoculation following his first dose of the Moderna (mRNA-1273) vaccine a few weeks prior. The nodule continued to progress in size after the second dose. A skin biopsy specimen of the nodule showed a diffuse dermal infiltrate of small to medium-sized lymphocytes with plasma cells and histiocytes. The infiltrate was composed of CD3+ T cells with CD20+ and CD79a+ B cells. The neoplastic B cells reacted with BCL-2 and were negative for BCL-6 and CD10. Kappa light chain restriction was identified by in situ hybridization. Gene rearrangement studies revealed kappa light chain monoclonality, confirming the diagnosis of PCMZLPD. The temporal association with the Moderna vaccination and the occurrence of the lesion at the inoculation site indicate a COVID-19 vaccination-induced PCMZLPD. This is one of the rare cases of PCMZLPD following COVID-19 vaccination.

Identifying and addressing unmet clinical needs in primary cutaneous B-cell lymphoma: A consensus-based paper from an ad-hoc international panel

Primary cutaneous B-cell lymphomas (PCBCLs) are lymphoproliferative disorders that appear on the skin without evidence of extracutaneous manifestations at the time of diagnosis. There is a lack of evidence-based guidelines for their clinical management due to the availability of very few large scale studies and controlled clinical trials. Here we present and discuss a series of major unmet clinical needs (UCNs) in the management of PCBCLs by a panel of 16 experts involved in research and clinical practice of PCBCL. The Panel produced recommendations on the appropriateness of the clinical decisions concerning the identified clinical needs and proposed research for improving the knowledge needed to solve them. Recommendations and proposals were achieved by multiple-step formalized procedures to reach a consensus after a comprehensive analysis of the scientific literature. Recommendations and proposals lay in the domain of classification uncertainties of PCBCL, optimization of diagnosis, optimization of prognosis, optimization of staging and critical issues on therapeutic strategies with particular focus on new treatments. These recommendations are intended for use not only by experts but above all by dermatologists and hematologists with limited experience in the field of PCBCLs as well as general practitioners.

Breast MALT Lymphoma: A Clinical, Histomorphologic, and Immunophenotypic Evaluation

Introduction. Primary breast extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma) is rare and understudied. Embryonically, mammary glands are developed as specialized skin appendages. It is possible that overlapping features exist between breast MALT lymphoma and primary cutaneous marginal zone lymphoma. Methods. We studied 5 primary and 6 secondary breast MALT lymphomas diagnosed in our institution during a 20-year period. Clinical and pathologic features of these lymphomas were analyzed and compared. Results. Most primary and secondary breast MALT lymphomas had similar clinical presentations as unilateral breast lesions without axillary lymphadenopathy. However, primary lymphomas tended to be diagnosed in older patients (median: 77 years old) than secondary lymphomas (median: 60 years old). Thyroid abnormality was a common finding in both primary (3/5) and secondary (5/6) lymphomas. Hashimoto's thyroiditis was diagnosed in one primary lymphoma. No distinct histopathologic findings were found in primary lymphomas. Features for primary cutaneous marginal zone lymphoma, including overexpression of IgG and IgG4 and high IgG4/IgG ratio, were absent in all primary but present in one secondary lymphoma with cutaneous origin. This secondary lymphoma also had expansion of CD30-positive cells. Conclusion. Primary breast MALT lymphoma does not share the distinctive features of primary cutaneous marginal zone lymphoma that set it apart from other extranodal marginal zone lymphomas. Having increased IgG- and IgG4-positive cells with a high IgG/IgG4 ratio in breast MALT lymphoma may indicate cutaneous origin. CD30 overexpression may be a feature seen in marginal zone lymphoma of cutaneous origin, which needs further studies to prove.

The Distinctive Nature of Thyroid MALT Lymphomas Including IRTA1 Expression

Mucosa-associated lymphoid tissue (MALT) lymphomas often express IgM and IRTA1 with only a minority demonstrating plasmacytic differentiation. However, like primary cutaneous marginal zone lymphoproliferative disorders (PCMZLPD), thyroid MALT lymphomas (T-MALT-L) frequently show plasmacytic differentiation and IgG positivity. Whether T-MALT-L share other features with PCMZLPD, including frequent IgG4 positivity and infrequent IRTA1 expression, and how IRTA1 staining compares to that in Hashimoto thyroiditis (HT) are unknown. Therefore, the clinicopathologic features of 18 T-MALT-L were assessed, and their IRTA1 expression compared with that in 5 HT cases. All T-MALT-L cases included a B-lymphoid component. Plasmacytic differentiation was present in 15 cases and was extensive in 12. Fourteen cases were IgG+ including 2 IgG4+ (12 κ+, 2 κ-/λ-). One case was IgAλ+. Plasmacytic cells were uniformly CD19+/CD56- but CD138- in 7/15 cases. IRTA1+ cells were present in 16/16 cases, ranging from scattered cells to >50%. They were often concentrated in "MALT ball"-type lymphoepithelial lesions, perifollicular regions, and sometimes in germinal centers. IRTA1 positivity was also present in all HT cases, although it was never very extensive and often had a perifollicular distribution, occasionally with sparse aggregates and positive cells within rare thyroid follicles. Thus, T-MALT-L share some features with PCMZLPD but are more similar to noncutaneous MALT lymphomas, with prominent lymphoepithelial lesions, ubiquitous although variable IRTA1 positivity, and infrequent IgG4 positivity. Plasmacytic differentiation is also common although CD138 loss is frequent and light chain staining may be absent. IRTA1 staining may help in the differential diagnosis with HT, although there is some overlap in staining patterns.

Immunoglobulin G4-Related Disease, Lymphadenopathy, and Lymphoma

Lymphadenopathy occurring in patients with immunoglobulin G4 (IgG4)-related disease, termed IgG4-related lymphadenopathy, shows morphologic heterogeneity and overlap with other nonspecific causes of lymphadenopathy including infections, immune-related disorders, and neoplasms. This review describes the characteristic histopathologic features and diagnostic approach to IgG4-related disease and IgG4-related lymphadenopathy, with comparison to nonspecific causes of increased IgG4-positive plasma cells in lymph nodes, and with emphasis on distinction from IgG4-expressing lymphoproliferative disorders.

Disease-Defining Molecular Features of Primary Cutaneous B-Cell Lymphomas: Implications for Classification and Treatment

Primary cutaneous B-cell lymphoma-primary cutaneous follicle center lymphoma; primary cutaneous marginal zone lymphoma; and primary cutaneous diffuse large B-cell, leg type-is a heterogeneous group with a variety of clinical and histological presentations. Until recently, the molecular bases of these disease subtypes have been unclear. We and others have identified the specific genetic characteristics that distinguish these subtypes from their respective systemic counterparts. These molecular features can improve diagnoses, determine the likelihood of concurrent or future systemic disease, and enable the rational design of novel clinical trials.

Recent advances in cutaneous lymphoma-implications for current and future classifications

The Revised European-American Classification of mature lymphoid neoplasms published in 1994 and the 2001, 2008 and 2016 WHO classifications that followed, were the product of international collaboration and consensus amongst haematopathologists, geneticists, molecular scientists and clinicians. Primary cutaneous lymphomas were fully incorporated into this process following the publication of the WHO-EORTC classification of cutaneous lymphomas in 2005. The definition, diagnostic criteria and recommended studies for primary cutaneous lymphoma continue to be refined. The 2022 International Consensus Classification represents the most recent update and an overview of all the main entities presenting primarily in the skin, together with the major changes in classification, are summarized herein. Primary cutaneous marginal zone lymphoma is segregated from other extranodal marginal zone lymphomas of mucosa-associated lymphoid tissue (MALT lymphoma) and downgraded to a lymphoproliferative disorder in line with its markedly indolent behaviour. In addition, two subtypes are recognised, based largely but not exclusively on whether they are heavy chain class-switched or IgM positive. Similarly, in keeping with a trend to greater conservatism, primary cutaneous acral CD8 positive T cell lymphoma is now also classified as a lymphoproliferative disorder. In addition, significant new insights into the biology of primary cutaneous lymphoma have also recently been forthcoming and will be presented. These studies have enhanced our knowledge of genetic, epigenetic and transcriptional changes in this group of diseases. They not only identify potential targets for novel therapies, but also raise as yet unanswered questions as to how we categorise cutaneous lymphomas, particularly with respect to relationships with similar lymphomas at extracutaneous sites.

A comparison of the International Consensus and 5th World Health Organization classifications of mature B-cell lymphomas

Several editions of the World Health Organization (WHO) classifications of lympho-hemopoietic neoplasms in 2001, 2008 and 2017 served as the international standard for diagnosis. Since the 4th WHO edition, here referred as WHO-HAEM4, significant clinico-pathological, immunophenotypic and molecular advances have been made in the field of lymphomas, contributing to refining diagnostic criteria of several diseases, to upgrade entities previously defined as provisional and to identify new entities. This process has resulted in two recent classifying proposals of lymphoid neoplasms, the International Consensus Classification (ICC) and the 5th edition of the WHO classification (WHO-HAEM5). In this paper, we review and compare the two classifications in terms of diagnostic criteria and entity definition, with focus on mature B-cell neoplasms. The main aim is to provide a tool to facilitate the work of pathologists, hematologists and researchers involved in the diagnosis and treatment of lymphomas.

The International Consensus Classification of Mature Lymphoid Neoplasms: a report from the Clinical Advisory Committee

Since the publication of the Revised European-American Classification of Lymphoid Neoplasms in 1994, subsequent updates of the classification of lymphoid neoplasms have been generated through iterative international efforts to achieve broad consensus among hematopathologists, geneticists, molecular scientists, and clinicians. Significant progress has recently been made in the characterization of malignancies of the immune system, with many new insights provided by genomic studies. They have led to this proposal. We have followed the same process that was successfully used for the third and fourth editions of the World Health Organization Classification of Hematologic Neoplasms. The definition, recommended studies, and criteria for the diagnosis of many entities have been extensively refined. Some categories considered provisional have now been upgraded to definite entities. Terminology for some diseases has been revised to adapt nomenclature to the current knowledge of their biology, but these modifications have been restricted to well-justified situations. Major findings from recent genomic studies have impacted the conceptual framework and diagnostic criteria for many disease entities. These changes will have an impact on optimal clinical management. The conclusions of this work are summarized in this report as the proposed International Consensus Classification of mature lymphoid, histiocytic, and dendritic cell tumors.

Clinical characteristics and outcomes of IgG4-positive marginal zone lymphoma: Systematic scoping review

Immunoglobulin G4 (IgG4)-positive marginal zone lymphoma (MZL) is rare and undefined. It is unclear whether IgG4-positive MZLs have as favorable an outcome as MZLs in general. Also, correlation with IgG4-related disease (IgG4-RD) and IgG4-positive MZLs is unknown. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for scoping reviews, we searched MEDLINE and EMBASE for all peer-reviewed articles using keywords including"IgG4" and "marginal zone lymphoma" from their inception to February 20, 2022. Twenty-two articles, including six observational studies and 24 cases from 16 case reports and case series, were included. Only one study had a comparative group, and the other five were exploratory observational studies. IgG4-positive MZLs commonly occurred in males (83.3%). It primarily involved ocular adnexa (41.7%) and skin (29.2%). Only 29.2% had concurrent IgG4-RD, and no expiration was noted. While most cases were treated with excision, resection, or clinical observation, 21.7% received rituximab-cyclophosphamide, doxorubicin, vincristine, and prednisone as a first-line treatment. This systematic review summarizes the current understanding of the characteristics of IgG4-positive MZLs. While there seems to be IgG4-RD-related and de novo IgG4-positive MZLs, future research needs to clearly define MZL with polyclonal IgG4-positive cells and IgG4-producing lymphoma. Further studies are critical to clarifying long-term prognosis and optimal surveillance planning.

Clinicopathologic Characteristics Associated with Prognosis in Ocular Extranodal Marginal Zone B Cell Lymphoma

Background and Objectives: Extranodal marginal zone lymphoma of the mucosa-associated lymphoid tissue (MALT) type is the most common subtype of the ocular adnexal lymphoma. Despite its excellent prognosis, some patients experience partial remission or progressive disease. We aimed to evaluate clinicopathologic differences in the treatment responder group by comparing complete remission (CR) and non-complete remission (non-CR). Materials and Methods: This study retrospectively reviewed 48 patients who were diagnosed with ocular adnexal MALT lymphoma at Ulsan University Hospital between March 2002 and August 2018. Patients who were followed up for less than 6 months were excluded. Histologic and clinical features were analyzed. The patients were divided into two groups: CR and non-CR. Results: Among the 48 patients, 33 achieved CR and 15 achieved non-CR during the median follow-up period of 40.00 months (range, 7-109 months). In univariable analysis, more patients tend to undergo treatment in the CR group, and post-radiotherapy (post-RT) SUVmax, PET and serum lactate dehydrogenase (LDH) levels were higher in the non-CR group (p = 0.043, p = 0.016, and p = 0.042, respectively). In a multivariable analysis, only application of treatment, including radiotherapy or chemotherapy with immunotherapy, was related to CR (odd ratio 7.301, 95% confidence interval 1.273-41.862, p = 0.026). In subgroup analysis according to the site of involvement, none of the variables were significant except for the post-RT SUVmax of PET and level of serum LDH in the non-conjunctiva group (p = 0.026, and p = 0.037, respectively). Seven (14.6%) patients had a recurrence, and those with a recurring site other than the primary site had a higher Ki-67 labeling index, although it was not statistically significant (9.56% vs. 18.00%, p = 0.095). Conclusions: Although belonging to the early stages, the non-CR rate was high in patients with high serum LDH levels, and recurred patients had higher Ki-67. Thus, considering active treatment is recommended in this group of patients.

Primary cutaneous Rosai-Dorfman-Destombes disease with features mimicking IgG4-related disease: A challenging case report and literature review

Rosai-Dorfman-Destombes disease (RDD) is a rare histiocytic disorder affecting lymph nodes as well as extranodal sites. Although cutaneous involvement in RDD is common, primary cutaneous RDD is a distinct and not well-documented entity with unknown aetiology and non-specific clinicopathological features. We report a case of a 57-year-old patient, who presented with an indolent skin nodule in the left sub-nipple area. Surgical excision was performed. Histological examination concluded to the diagnosis of cutaneous RDD with histological features mimicking IgG4-related disease. The diagnosis of systemic RDD with cutaneous involvement was ruled out after exclusion of extracutaneous involvement. No recurrence or systemic progression was observed during follow-up. The diagnosis of primary cutaneous RDD is very uncommon and hence is challenging for pathologist and dermatologist especially with features of IgG4-related disease. Careful systemic and microscopic examinations help in establishing the appropriate diagnosis.

Cutaneous Involvement in Diseases with Plasma Cell Differentiation: Diagnostic Approach

Neoplasms with plasma cell differentiation may occasionally involve the skin. Cutaneous lesions may represent the first sign of an underlying systemic plasma cell malignancy, such as multiple myeloma, or the skin itself may be the primary site of occurrence of a hematological tumor with plasma cell differentiation. Starting from examples encountered in our daily practice, we discussed the diagnostic approach pathologists and clinicians should use when faced with cutaneous lesions with plasma cell differentiation. Cases of primary cutaneous marginal zone lymphoma, localized primary amyloidosis/amyloidoma, and cutaneous manifestations (secondary either to multiple myeloma or to plasmablastic lymphoma) are discussed, focusing on the importance of the adequate patient’s work-up and precise clinicopathological correlation to get to the correct diagnosis and appropriate treatment. The pertinent literature has been reviewed, and the clinical presentation, pathological findings, main differential diagnoses, treatment, and outcome of neoplasms with plasma cell differentiation involving the skin are discussed.

IRTA1 positivity helps identify a MALT-lymphoma-like subset of primary cutaneous marginal zone lymphomas, largely but not exclusively defined by IgM expression

BACKGROUND

It has been proposed that primary cutaneous marginal zone lymphomas (PCMZLs) include a MALT-lymphoma-like IgM+ subset and a class-switched subset, which is unlike most other MALT lymphomas. Whether expression of the MALT lymphoma-associated biomarkers IRTA1 and MNDA would support this concept and whether they might help explain why some patients have both subtypes is uncertain.

METHODS

Twenty-five PCMZLs from 21 patients were stained for IRTA1 by in situ hybridization and for MNDA by immunohistochemistry. In two patients, polymerase chain reaction (PCR)-based B-cell clonality studies were performed on biopsy specimens of metachronous lesions, which expressed different heavy chains. All results were correlated with the histopathologic and clinical findings.

RESULTS

Five of six IgM+ PCMZLs were IRTA1+ vs three of 18 evaluable class-switched cases (P = 0.0069). Two of the class-switched IRTA1+ cases were in patients with clonally-related IRTA1+ IgM+ PCMZLs. IRTA1 positivity showed a statistically significant correlation with several MALT-lymphoma-associated histopathologic findings. In contrast, all PCMZL cases showed at least some MNDA expression with no differences between IgM+ and class-switched cases.

CONCLUSIONS

IRTA1 identifies MALT-lymphoma-like PCMZLs that are largely but not exclusively IgM+. This supports the concept of two PCMZL subsets but suggests their distinction should not be based solely on their heavy chain expression.

Upregulated Expression of Activation-Induced Cytidine Deaminase in Ocular Adnexal Marginal Zone Lymphoma with IgG4-Positive Cells

Immunoglobulin G4-related disease (IgG4-RD) is a systemic disorder characterized by tissue fibrosis and intense lymphoplasmacytic infiltration, causing progressive organ dysfunction. Activation-induced cytidine deaminase (AID), a deaminase normally expressed in activated B-cells in germinal centers, edits ribonucleotides to induce somatic hypermutation and class switching of immunoglobulin. While AID expression is strictly controlled under physiological conditions, chronic inflammation has been noted to induce its upregulation to propel oncogenesis. We examined AID expression in IgG4-related ophthalmic disease (IgG4-ROD; n = 16), marginal zone lymphoma with IgG4-positive cells (IgG4+ MZL; n = 11), and marginal zone lymphoma without IgG4-positive cells (IgG4- MZL; n = 12) of ocular adnexa using immunohistochemical staining. Immunohistochemistry revealed significantly higher AID-intensity index in IgG4-ROD and IgG4+ MZL than IgG4- MZL (p < 0.001 and = 0.001, respectively). The present results suggest that IgG4-RD has several specific causes of AID up-regulation in addition to inflammation, and AID may be a driver of oncogenesis in IgG4-ROD to IgG4+ MZL.

Utility of gastric biopsy in diagnosing IgG4-related gastrointestinal disease

The utility of gastric biopsy for diagnosing immunoglobulin (Ig)G4-related gastrointestinal disease (IgG4-GID) remains unclear. Bottom-heavy plasmacytosis (BHP) is a distinct feature of IgG4-GID. To clarify the feasibility of using gastric biopsies to diagnose BHP in IgG4-GID, we analyzed the histological features and immunostaining of gastric biopsy specimens from 31 known IgG4-related disease (IgG4-RD) patients and we assessed the presence of BHP in 1696 consecutive routine gastric biopsies. Cases with both >10 IgG4-positive plasma cells per high-power field and an IgG4/IgG-positive ratio >40% were defined as IgG4-high. Ten of the 31 IgG4-RD patients were concluded to have IgG4-GID, in which IgG4-positive plasma cells were notably detected at the deeper part of the mucosa. Six cases displayed BHP whereas the remaining four cases showed transmural infiltration with concomitant Helicobacter pylori-associated gastritis. In addition to BHP, we identified two unique histologic features for IgG4-GID: plasmacytic aggregation in the muscularis mucosae and permeative plasmacytic infiltration between fundic glands in the non-atrophic mucosa. Six of the routine cases (0.35%) displayed BHP, including a case with IgG4-RD. IgG4-GID can be suspected by the presence of gastric biopsy specimens with characteristic histological features. Such cases are recommended to undergo further examinations to determine whether IgG4-RD is present.

Kappa and lambda immunohistochemistry and in situ hybridization in the evaluation of atypical cutaneous lymphoid infiltrates

BACKGROUND

Atypical cutaneous lymphoid infiltrates are challenging lesions in dermatopathology. We present a summary of the literature regarding kappa and lambda immunohistochemistry (IHC) and in situ hybridization (ISH) in the evaluation of atypical cutaneous or mucosal lymphoid infiltrates.

METHODS

Relevant articles from 1967 to 2018 in the English language were identified and summarized. In the absence of larger studies, case series of n ≥ 3 were included.

RESULTS

Sixty-three articles assessing kappa and lambda IHC and/or ISH were identified. Most focused on marginal zone lymphomas. Other lymphomas included follicle center lymphoma, diffuse large B-cell lymphoma, chronic lymphocytic leukemia/small lymphocytic lymphoma, mantle cell lymphoma, lymphoplasmacytic lymphoma, plasmablastic lymphoma, multiple myeloma, monoclonal gammopathy of undetermined significance, and polyneuropathy, organomegaly, endocrinopathy, monoclonal protein, skin changes (POEMS). Non-neoplastic lesions included reactive lymphoid hyperplasia, cutaneous plasmacytosis, connective tissue disease, IgG4-related disease, acrodermatitis chronic atrophicans, Zoon balanitis, dermatitides, and infiltrates around epithelial dysplasias/neoplasias.

CONCLUSION

Kappa and lambda IHC and ISH are useful tools in the evaluation of cutaneous B-cell lymphomas and plasma cell neoplasms. The literature supports that the detection of light-chain restriction by IHC and ISH is one of the most useful findings in the differential diagnosis of reactive lymphoid hyperplasia vs B-cell lymphoma with plasmacytic differentiation.

How I Diagnose Primary Cutaneous Marginal Zone Lymphoma

OBJECTIVES

Primary cutaneous marginal zone lymphoma (PCMZL) is 1 of the 3 major subtypes of primary cutaneous B-cell lymphoma. The diagnosis of PCMZL may be challenging, as the differential diagnosis includes benign cutaneous lymphoproliferations as well as other primary or secondary cutaneous B-cell or T-cell lymphomas. This review describes our approach to the diagnosis of PCMZL.

METHODS

Two cases are presented that illustrate how we diagnose each of the 2 subtypes of PCMZL. The clinicopathologic features of PCMZL and the ways in which these cases can be distinguished from both benign and other neoplastic entities are emphasized.

RESULTS

A definitive diagnosis of PCMZL requires the incorporation of histologic and immunophenotypic features, molecular genetic studies in some cases, and just as importantly, clinical findings. Emerging data suggest that the heavy chain class-switched cases may be more like a clonal chronic lymphoproliferative disorder.

CONCLUSIONS

The 2 subtypes of PCMZL create different diagnostic challenges and require the use of a multiparameter approach. Although very indolent, it is important to distinguish PCMZLs from reactive proliferations, because they frequently recur and may require antineoplastic therapies. It is also critical to distinguish PCMZLs from other B- or T-cell lymphomas so that patients are properly evaluated and not overtreated.

Treatment outcomes of IgG4-producing marginal zone B-cell lymphoma: a retrospective case series

IgG4-producing marginal zone B-cell lymphomas (MZLs) have been recently proposed as a subtype of MZLs. Despite the abundant literature on pathophysiological features of this type of lymphoma, only a few retrospective studies pertaining to the treatment outcomes have been reported, and its prognosis remains unclear. We retrospectively analyzed seven patients with IgG4-producing MZLs diagnosed at our institute, with specific reference to treatment and outcomes. The median age was 69.0 years (55-79), and all were males. The median follow-up period was 66.6 months (8-121). All patients had localized disease; four patients had tumors of the ocular adnexa, whereas two had retroperitoneal tumors. Five patients were treated with irradiation (30 Gy/15 fr) (n = 4) or surgery (n = 1), resulting in tumor reduction. Two patients were treated by chemotherapy or irradiation. Among them, one commenced rituximab monotherapy, which led to an inadequate reduction of the tumor. Subsequent irradiation induced complete response (CR). The other patient experienced repeated relapses during follow-up and finally achieved CR by combination chemotherapy. Treatment was well tolerated in all cases, and none of the patients showed disease progression at the last follow-up visit. Our results indicate that the standard treatments for MZLs are generally appropriate for IgG4-producing MZL.

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.

Navigating the cutaneous B-cell lymphomas: avoiding the rocky shoals

In recent years great progress has been made in understanding the classification of lymphomas. The integration of morphologic, clinical, immunophenotypic, and molecular features provides a rational basis for defining disease entities and has led to worldwide consensus. Hematopathologists and dermatopathologists have worked together to define those lymphomas that are present most commonly in the skin. Some cutaneous lymphomas have distinctive features and differ from their nodal counterparts. This is most evident in the delineation of primary cutaneous follicle center lymphoma and primary cutaneous marginal zone lymphoma. Both are very indolent, with low risk to spread beyond the skin. Primary cutaneous marginal zone lymphoma shows evidence of immunoglobulin class switching, as distinct from involvement by other extranodal marginal zone lymphomas of MALT type, which may involve the skin secondarily. Some have suggested that primary cutaneous marginal zone lymphoma may be considered a benign clonal expansion, probably driven by antigen. Many cutaneous lymphomas share biological and clinical features with their systemic counterparts. For example, primary cutaneous large B-cell lymphoma, leg type, exhibits a similar gene expression and molecular profile as diffuse large B-cell lymphoma of the activated B-cell type, especially for those cases arising in other extranodal sites. In addition, Epstein-Barr virus plays a role in many cutaneous lesions including mucocutaneous ulcer, plasmablastic lymphoma, and even some cases of marginal zone lymphoma. These EBV-driven conditions may present primarily in the skin, but also involve other mainly extranodal sites. Thus, it is evident that some cutaneous and systemic lymphomas are driven by common pathogenetic mechanisms, necessitating an integrated approach for the classification of lymphoma in all sites.

Marginal zone B-cell lymphoma: lessons from Western and Eastern diagnostic approaches

Marginal zone B-cell lymphomas (MZLs) are a group of clinically indolent B-cell lymphomas postulated to derive from memory B lymphocytes in the 'marginal zone' of secondary lymphoid tissue. Today, MZL is recognised as a nosological umbrella term encompassing distinct entities with some shared phenotypic and genotypic features, including extranodal marginal zone B-cell lymphoma (EMZL) or mucosa-associated lymphoid tissue (MALT) lymphoma, splenic MZL, and nodal MZL, accounting for approximately 70%, 20%, and 10% of MZLs, respectively. These lymphomas share some phenotypic and genotypic features and have some variants and related provisional diseases, but are different in regards to their clinical and molecular characteristics. In addition, they are frequently associated with chronic antigenic stimulation represented either by infectious agents, particularly bacteria and viruses, or autoimmune diseases as exemplified by Sjögren syndrome, Hashimoto thyroiditis, and newly recognised IgG4-related disease. Furthermore, several chromosomal translocations have been identified in EMZL. In this review, we will focus on the updated histopathological criteria and the main problems with differential diagnoses in order to aid the diagnostic approach in our routine practice.

Mucosa-associated lymphoid tissue lymphoma on right lower eyelid previously diagnosed as lymphoid hyperplasia

Mucosa-associated lymphoid tissue (MALT) lymphoma is an uncommon form of non-Hodgkin lymphoma involving the mucosa-associated lymphoid tissue. Most commonly affected organ is the stomach. But, it could affect almost every organ in the whole body. If they have suspicious lesion, excision biopsy could be made. For staging, blood test including blood smear, abdomen and chest tomography or scan will be checked. Also, bone marrow test can be done if it is needed. The patient had visited the clinic for palpable mass on right lower eyelid. With excisional biopsy, it was diagnosed as lymphoid hyperplasia on pathologic test. But 2 years later, the patient came with recurrent symptom for our department with worry. At that time, we recommended excisional soft tissue biopsy under general anesthesia. Unfortunately, it was revealed MALT lymphoma on pathologic finding. It turned out to be stage 3 in Ann Arbor staging system without B symptoms. Hematologic consultation was made and she was treated with adjuvant chemotherapy for eight cycles to complete remission. We report a case of MALT lymphoma on subcutaneous tissue at right lower eyelid previously diagnosed as lymphoid hyperplasia.

IgG4-related disease: review of the histopathologic features, differential diagnosis, and therapeutic approach

Immunoglobulin G4-related disease (IgG4-RD) is an uncommon disorder that demonstrates characteristic clinicopathologic features including sclerosing lesions with storiform fibrosis, increased IgG4+ plasma cells with an increased IgG4+/IgG+ plasma cell ratio, obliterative phlebitis, and often an increased serum IgG4 level. This review summarizes the characteristic histopathologic and clinical features of IgG4-RD with detailed discussion of the histopathologic characteristics of the most commonly involved anatomic sites. We also present recent advances in our understanding of the pathophysiologic mechanisms of IgG4-RD and discuss updates on the treatment, prognosis, and outcomes of this rare disease, including discussion of the possible association between IgG4-RD and malignancy.

Cutaneous Hematolymphoid and Histiocytic Proliferations in Children

This article focuses on cutaneous hematopoietic neoplasms that are more likely to be encountered in the pediatric age-group and includes both lymphoproliferative and histiocytic disorders. The cutaneous hematologic disorders in children have a different epidemiologic profile to what is seen during adulthood. Although mycosis fungoides is the most frequent form of cutaneous lymphoma in adults, it is very rare in children. Because lymphoblastic leukemias and lymphomas are more frequent in the pediatric setting, cutaneous leukemic infiltrates are relatively common in this age-group. Similarly, histiocytic disorders are more common in children, particularly Langerhans cell histiocytosis and juvenile xanthogranuloma. Notably, the histiocytic disorders have undergone significant modifications on their nomenclature in the basis of the molecular characteristics that are present in them. A summary of the most frequent cutaneous hematopoietic disorders in children will be discussed further in this review.

Cutaneous B-cell lymphomas - pathogenesis, diagnostic workup, and therapy

Cutaneous B-cell lymphomas (CBCLs) comprise a group of mature lymphoproliferative B-cell disorders that primarily affect the skin. Characterized by great biological and clinical variability among its various subtypes, CBCLs fundamentally differ from primary nodal or systemic B-cell lymphomas. Given their uncomplicated course and excellent prognosis, lymphoma classifications rank primary cutaneous marginal zone lymphoma (PCMZL) and primary cutaneous follicle center lymphoma (PCFCL) as indolent CBCLs. By contrast, diffuse large B-cell lymphoma, leg type (DLBCL-LT) in particular, represent more aggressive lymphoma variants associated with a poorer prognosis. Therapeutic decisions and diagnostic procedures are based on the exact histological and immunohistochemical classification as well as the exclusion of systemic involvement and thus differentiation from nodal and systemic lymphomas. In this context, the diagnostic workup should also include molecular biology methods. Primary therapeutic options for indolent CBCL lesions include surgery and radiation therapy, as well as systemic treatment with rituximab (anti-CD20 antibody) in case of dissemination. More aggressive CBCLs usually require a combination of rituximab and polychemotherapy, primarily the CHOP regimen or modifications thereof. Given that the pathogenesis and biology of CBCLs has not been conclusively elucidated, and given the limited therapeutic armamentarium available, there is great need for comprehensive research, especially with respect to DLBCL-LT.

The genetic landscape of dural marginal zone lymphomas

The dura is a rare site of involvement by marginal zone lymphoma (MZL) and the biology of dural MZL is not well understood. We performed genome-wide DNA copy number and targeted mutational analysis of 14 dural MZL to determine the genetic landscape of this entity. Monoallelic and biallelic inactivation of TNFAIP3 by mutation (n=5) or loss (n=1) was observed in 6/9 (67%) dural MZL exhibiting plasmacytic differentiation, including 3 IgG4+ cases. In contrast, activating NOTCH2 mutations were detected in 4/5 (80%) dural MZL displaying variable monocytoid morphology. Inactivating TBL1XR1 mutations were identified in all NOTCH2 mutated cases. Recurrent mutations in KLHL6 (n=2) and MLL2 (n=2) were also detected. Gains at 6p25.3 (n=2) and losses at 1p36.32 (n=3) were common chromosomal imbalances, with loss of heterozygosity (LOH) of these loci observed in a subset of cases. Translocations involving the IGH or MALT1 genes were not identified. Our results indicate genetic similarities between dural MZL and other MZL subtypes. However, recurrent and mutually exclusive genetic alterations of TNFAIP3 and NOTCH2 appear to be associated with distinct disease phenotypes in dural MZL.

Frequent immunoglobulin G4 expression in a common variant of primary cutaneous marginal zone B-cell lymphoma

Immunoglobulin (Ig)G4 expression was recently observed in a proportion of primary cutaneous marginal zone B-cell lymphoma (PCMZL) with plasmacytic differentiation. IgG4-related disease is characterised by polyclonal lymphoplasmacytic infiltration with IgG4 expression, storiform fibrosis and obliterative phlebitis in histopathology. Here we report three cases of common variants of PCMZL with predominant and varied IgG4 expression, suggesting there is an underlying clonal progression between these two entities.

Atypical IgG4+ Plasmacytic Proliferations and Lymphomas: Characterization of 11 Cases

OBJECTIVES

To report the clinicopathologic features of monotypic immunoglobulin G4+ (IgG4+) lymphoid and plasmacytic proliferations.

METHODS

Cases were identified from the pathology files. Pathology and clinical materials were reviewed.

RESULTS

Eleven cases of monotypic IgG4+ proliferations were identified at nodal, orbital, or salivary sites. Six cases (three men, three women; age, 57-94 years) met criteria for lymphoma or plasma cell neoplasia. Most contained frequent Mott cells. Five cases (three men, two women; age, 40-80 years) had restricted proliferations of atypical/monotypic IgG4+ plasma cells in a background of reactive lymphoid hyperplasia or inflammation.

CONCLUSIONS

Monotypic IgG4+ proliferations include lymphomas, plasmacytic neoplasms, and a previously uncharacterized group of proliferations not meeting criteria for conventional hematolymphoid neoplasia. Distinct features included prominent Mott cells and/or monotypic plasma cells within follicles. The proliferations were infrequently associated with IgG4-related disease (IgG4-RD). Our findings raise questions regarding the relationship between clonal IgG4+ proliferations, reactive/inflammatory processes, and IgG4-RD.

[Treatment of indolent cutaneous B‑cell lymphoma]

Primary cutaneous B‑cell lymphomas are rarely encountered and represent 25% of all cutaneous lymphomas. Follicular B‑cell lymphoma and marginal zone lymphoma belong to indolent subtypes which as a rule have no systemic dissemination and, thus, a mostly unchanged life expectancy. Therefore, skin-directed treatment options such as excision or radiotherapy are usually sufficient to control the disease. In contrast, cutaneous diffuse large B‑cell lymphoma and EBV-associated B‑cell lymphomas of the skin belong to more aggressive entities which demand a systemic first-line upfront therapy with R‑CHOP. Nevertheless, mortality is still high and comparable to that of systemic/nodal large B‑cell lymphomas so that the identification of pathogenetic driver mutations or novel therapeutic targets may pave the way to better target-oriented therapies.

IgG4-related skin disease may have distinct systemic manifestations: a systematic review

IgG4-related disease (IgG4-RD) is an increasingly prevalent protean multisystem disorder characterized by single or multi-organ infiltration of IgG4-bearing plasma cells. Skin involvement has been recognized and is relevant to proper diagnosis. A systematic literature review of 50 cases involving the skin reveals that patients with IgG4-related skin disease show predominant involvement of the head and neck and have a distinct pattern of systemic involvement, also favoring the head and neck - lymphatics, orbit, salivary, and lacrimal glands - but generally lacking pancreaticobiliary involvement (16% of cases), which by contrast is a predominant manifestation in systemic IgG4-RD (60% with pancreaticobiliary involvement). We summarize clinical and pathologic descriptive data from this systematic review. We review differential diagnosis and propose a diagnostic scheme for stratifying probability of disease based upon comprehensive integration of clinical, histopathologic, and laboratory data. Plasmacyte infiltration and storiform fibrosis are prominent in IgG4-related skin disease, but obliterative venulitis is less common than in the prototypical IgG4-related disease manifestation of autoimmune pancreatitis. IgG4 tissue and serum values, with a mean (±95% CI) in the reviewed cases of 132.8 ± 32.6 IgG4-positive plasma cells per high-power field and 580 ± 183.8 mg/dl, respectively, are incorporated into the suggested criteria. The distinct set of manifestations identified by this systematic review and the proposed diagnostic considerations, while requiring further validation in prospective studies, highlight the need to consider that IgG4-related skin disease defines a unique systemic disease complex along the spectrum of IgG4-RD.

B-Zell-Lymphome der Haut - Pathogenese, Diagnostik und Therapie

Primär kutane B-Zell-Lymphome (PCBCL) beschreiben reifzellige lymphoproliferative Erkrankungen der B-Zell-Reihe, die primär die Haut betreffen. Die Biologie und der klinische Verlauf der einzelnen PCBCL-Subtypen variieren untereinander stark und unterscheiden sich grundsätzlich von primär nodalen und systemischen B-Zell-Lymphomen. Primär kutane Marginalzonenlymphome (PCMZL) und primäre kutane follikuläre Keimzentrumslymphome (PCFCL) werden auf Grund ihres unkomplizierten Verlaufs und ihrer exzellenten Prognose zu den indolenten PCBCL gezählt. Demgegenüber stellen die diffus großzelligen B-Zell-Lymphome, hauptsächlich vom Beintyp (DLBCL, LT) die aggressiveren PCBCL-Varianten mit schlechterer Prognose dar. Für die Ausbreitungsdiagnostik und die Therapieentscheidung sind eine genaue histologische und immunhistochemische Klassifizierung sowie der Ausschluss einer systemischen Beteiligung in Abgrenzung zu nodalen oder systemischen Lymphomen notwendig. Die Diagnostik sollte dabei durch molekularbiologische Untersuchungen unterstützt werden. Therapeutisch stehen für die indolenten PCBCL primär operative und radioonkologische Maßnahmen im Vordergrund sowie eine Systemtherapie mit dem CD20-Antikörper Rituximab bei disseminiertem Befall. Die aggressiveren Varianten sollten in erster Linie mit Kombinationen aus Rituximab und Polychemotherapieschemata wie z. B. dem CHOP-Schema oder Modifikationen davon behandelt werden. Auf Grund der in allen seinen Einzelheiten noch nicht vollständig verstandenen Pathogenese und Biologie sowie des begrenzten Therapiespektrums der PCBCL besteht hier, speziell beim DLBCL, LT, noch erheblicher Forschungsbedarf.

Immunoglobulin G4-Related Lymphadenopathy

Immunoglobulin G4-related lymphadenopathy (IgG4-RLAD) occurs in the setting of extranodal IgG4-related disease (IgG4-RD), an immune-mediated process described in many organ systems characterized by lymphoplasmacytic infiltrates with abundant IgG4-positive plasma cells and fibrosis. Although the morphologic features in the lymph node sometimes resemble those seen at the extranodal sites, 5 microscopic patterns have been described, most of which resemble reactive lymphoid hyperplasia. This morphologic variability leads to unique diagnostic challenges and a broad differential diagnosis. As IgG4-RD may be exquisitely responsive to steroids or other immunotherapy, histologic recognition and inclusion of IgG4-RLAD in the differential diagnosis is vital.

Cutaneous marginal zone lymphomas

Primary cutaneous marginal zone lymphoma (CMZL) is one of the major primary B-cell lymphomas of skin. Two types are recognized: a more common class-chain switched CMZL, and a much less common IgM+ CMZL. The extremely indolent course, together with other features distinct from most other MALT lymphomas, has led some to question whether at least the class-switched cases should be considered an overt lymphoma.

IgG4-producing lymphoma arising in a patient with IgG4-related disease

We herein report a case in which an IgG4-producing lymphoma arose in a patient with a previous diagnosis consistent with an IgG4-related disease. A 43-year-old man presented with enlarged cervical lymph nodes and was treated with steroids and radiation for what was initially assumed to be Kimura's disease, although the lesions were later histologically re-diagnosed as IgG4-related lymphadenopathy. Fourteen years later, when the patient was 58-years-old, he presented with retroperitoneal fibrosis and swollen lymph nodes. The suspicious lesions were not histologically examined as the patient did not give consent. However, the serum IgG4 concentration was high (1400 mg/dL) and he was clinically diagnosed with systemic IgG4-related disease. Although steroid administration reduced the size of the lesions, tapering the dose finally resulted in systemic, prominently enlarged lymph nodes. Analysis of the biopsy specimen revealed that these multiple lymph node lesions were marginal zone B cell lymphomas that themselves expressed IgG4. Complete remission was achieved after a total of six courses of chemotherapy including rituximab. This case suggests that the infiltrating IgG4-expressing cells observed in IgG4-related disease can clonally expand to malignant lymphomas.