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

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.

Increased IgG4+ plasma cells are common in excised lymph nodes from children and adolescents without IgG4-related disease

Lymphadenopathy is a common finding in patients with IgG4-related disease (IgG4-RD) and often associated with increased IgG4+ plasma cells in this setting. The histologic features of so-called IgG4-related lymphadenopathy (IgG4-LAD) have seldom been investigated in children and adolescents, and step-wise progression to extranodal IgG4-RD has not been described. This study was performed to further evaluate the frequency, pathologic features, and clinical significance of IgG4-LAD-like histologic changes in the pediatric setting. We analyzed 37 benign lymph nodes collected semi-consecutively from children aged 0-18 years at our institution for both absolute and relative IgG4+ plasma cell abundance and recurrent histomorphologic patterns associated with IgG4-LAD. The combination of IgG4+/IgG+ plasma cell ratio >40% and IgG4+ plasma cell count ≥50 were considered as IgG4-LAD-like per expert consensus guidelines. Seven cases (19%) met both diagnostic criteria. The dominant histomorphologic patterns were follicular hyperplasia (n = 6), interfollicular expansion (n = 3), and progressive transformation of germinal centers (n = 3). Extranodal manifestations of IgG4-RD were not identified in this cohort (38 months average follow-up). Instead, clinical and laboratory findings indicated that lymph node enlargement in most patients could likely be attributed to alternative processes including antecedent dentistry, concurrent infection, and incipient Crohn's disease. Our findings suggest that the histologic features of IgG4-LAD are likely much more common in children and adolescents than previously recognized, often existing in complex with common reactive lymphadenopathies. The diagnostic value of routine immunohistochemical assessment for IgG4+ plasma cells in benign lymph nodes from pediatric patients without established extranodal IgG4-RD and/or other supportive clinical and laboratory data is therefore uncertain.

Isolated Light Chain-restricted Germinal Centers are Common in Follicular Hyperplasia by Ultrasensitive In Situ Hybridization

Ultrasensitive bright-field RNA in situ hybridization (BRISH) can be used to detect lower levels of light chain expression than immunohistochemical stains or conventional colorimetric RNA in situ hybridization. In this study, we retrospectively reviewed 77 lymph node specimens with follicular hyperplasia and kappa/lambda BRISH performed as part of the diagnostic evaluation. Thirty-two of the specimens had ≥1 germinal center(s) (GC) showing light chain restriction (14 specimens with lambda-restricted GC, 9 with kappa-restricted GC, and 9 with separate kappa-restricted or lambda-restricted GC). In all but 1 specimen, the light chain-restricted GC represented a minority of the total GC (average: 10%, range: 0.2% to 60%). There was no significant difference in age, sex, type of biopsy (core vs. excision), number of GCs, proportion of cases with a light chain-restricted B-cell population by flow cytometry, or proportion of cases with a positive IgH gene rearrangement study between the specimens with and without restricted GCs. In our cohort of follicular hyperplasia cases, BRISH identified light chain-restricted GC more frequently than flow cytometry identified a monotypic B-cell population. Our findings highlight the potential for overinterpretation of light chain restriction in limited samplings such as fine needle aspiration cell blocks or core needle sampling and reinforce that interpretation of BRISH staining needs to occur in the context of the morphologic features including tissue architecture and results of additional immunohistochemical stains.

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.

IgG4-related disease: an analysis of the clinicopathological spectrum: UK centre experience

AIM

To retrospectively evaluate the characteristic clinicopathological spectrum in patients with suspicion of IgG4-related disease (IgG4RD).

METHODS

Winpath histology database from January 2011 to April 2018 identified all suspected IgG4RD cases wherein IgG4 immunohistochemistry was performed. The histology slides were reviewed to categorise cases into Boston criteria groups-highly suggestive of IgG4RD, probable IgG4RD and insufficient evidence. Information regarding clinical data, treatment received, follow-up and serum IgG4 levels was obtained from medical records and AllScripts Patient Administration System (APAS) clinical database.

RESULTS

The study included 204 patients and the most common sites of biopsy/resection were pancreas and duodenum. The most common clinical presentation was fibroinflammatory lesion or mass/lump. On histology, 54/204 (26.47%) cases showed typical storiform fibrosis, 65/204 (32.64%) had >10 IgG4+ plasma cells per high power field and only one case showed thrombophlebitis (0.49%). There were 14/204 (6.78%) cases categorised as highly suggestive of IgG4RD; 8 of these showed high serum IgG4 levels and were managed clinically as true IgG4RD.

CONCLUSION

Histological diagnosis of IgG4RD remains challenging, as not all characteristic features are always present especially in small biopsies. Due to the novelty of its experience, fear of over diagnosis in the context of malignancy and features overlapping with diseases of similar clinical scenario, diagnosis of IgG4RD has become more puzzling. Further multicentre clinical trials/studies are advisable.

Light Chain-Restricted Plasmacytoid Cells in Hyperplastic Germinal CentersA Clinicopathologic Investigation

OBJECTIVES

Follicular hyperplasias (FHs) with light chain-restricted (LCR) plasmacytoid/plasma cells (PCs) within germinal centers (GCs) based on immunohistochemistry (IHC)/in situ hybridization (ISH) can potentially lead to diagnostic error. This study aims to better characterize such cases, including their clinical implications.

METHODS

LC expression by IHC/ISH was quantitatively assessed in GCs of 17 FHs with LCRGCs. BCL2, CD10, BCL6, BCL2, immunoglobulin (Ig) heavy chains, IgG4, and Epstein-Barr encoding region stains were performed. In total, 8 cases had polymerase chain reaction (PCR)-based clonality studies.

RESULTS

All cases showed FH, including 4 with progressively transformed GCs (PTGCs); 0.8% to 52% (median, 21%) of the GCs were LCR; 13 of 17 had both κ- and λ-LCRGCs, and 4 of 17 had only κ-LCRGCs; 7 of 16 had prominent intrafollicular IgG4-positive cells. One case demonstrated BCL2-positive cells in focal LCRGCs but lacked BCL2 rearrangement. B-cell monoclonality was demonstrated in 3 of 8 cases (only after microdissection). Seven patients had autoimmune disorders, and 1 had had a transplant. Three patients had a history of lymphoma, 1 developed lymphoma, and 1 developed lymphomatoid granulomatosis subsequently.

CONCLUSIONS

FHs with LCRGC by IHC/ISH are typically not associated with the development of lymphoma, even though they can express BCL2 and show monoclonality by PCR. They may be associated with increased intrafollicular IgG4-positive cells, PTGC, and autoimmunity.

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.

IgG4-related Lymphadenopathy: A Comparative Study of 41 Cases Reveals Distinctive Histopathologic Features

Lymphadenopathy is common in patients with immunoglobulin G4-related disease (IgG4-RD). However, the described histopathologic features of IgG4-related lymphadenopathy have been shown to be largely nonspecific. In an attempt to identify features specific for nodal IgG4-RD we examined the histopathologic features of lymph nodes from 41 patients with established IgG4-RD, with comparison to 60 lymph nodes from patients without known or subsequent development of IgG4-RD. An increase in immunoglobulin (Ig) G4-positive plasma cells >100/HPF and IgG4/IgG ratio >40% was identified in 51% of IgG4-RD cases and 20% of control cases. Localization of increased IgG4-positive plasma cells and IgG4/IgG ratio to extrafollicular zones was highly associated with IgG4-RD, particularly when identified in regions of nodal fibrosis (P<0.0001; specificity: 98.3%), or in the context of marked interfollicular expansion (P=0.022; specificity: 100%). Other features characteristic of IgG4-RD included frequent eosinophils associated with IgG4-positive plasma cells, phlebitis (P=0.06), and perifollicular granulomas (P=0.16). The presence of an isolated increase in intrafollicular IgG4-positive plasma cells and IgG4/IgG ratio was more frequently present in control cases than IgG4-RD (P<0.0001). This study confirms that increased IgG4-positive plasma cells and IgG4/IgG ratio are neither sensitive nor specific for the diagnosis of IgG4-related lymphadenopathy, and most described morphologic patterns are nonspecific. In contrast, nodal involvement by IgG4-rich fibrosis akin to extranodal IgG4-RD or diffuse interfollicular expansion by IgG4-positive plasma cells are highly specific features of true IgG4-related lymphadenopathy. Our findings provide for a clinically meaningful approach to the evaluation of lymph nodes that will assist pathologists in distinguishing IgG4-related lymphadenopathy from its mimics.

Camacho M, Cunha B, Alkatan H, Xavier N. Plasma cell IgG4 positivity in orbital biopsies of non-IgG4-related conditions

The IgG4-related disease (IgG4-RD) is a systemic condition defined as a fibro-inflammatory disorder, characterized by the occurrence of tumor-like lesions in multiple organs including the eye adnexa. The main diagnostic criterion is based on histopathological findings, especially on the IgG4⁺/IgG⁺ plasma cell ratio. In this article, we reviewed the literature of non-IgG4-RD orbital conditions with IgG4 positivity. There were 20 reports of inflammatory non-IgG4-RD orbital lesions and 14 reports of orbital lymphoid proliferations with significant IgG4 positivity. The role of plasma cells IgG4 in the pathogenesis of non-IgG4-RD is not clear. Considering the large spectrum of diseases caused by a variety of different etiopathogenic mechanisms, we think that the common denominator of IgG4⁺ in these conditions might be related to the peculiar properties of down regulation of immune response of the IgG4 and not to a specific link to IgG4-RD.

IgG4-rich reactive lymphoid hyperplasia of the lacrimal gland

We describe an otherwise healthy 24-year-old woman with reactive lymphoid hyperplasia of one lacrimal gland. She was found to have modest elevation of serum IgG4 and high density of IgG4+ plasma cells in her lacrimal gland, ranging from 40% to 60% of IgG+ plasma cells. The patient transiently responded to systemic corticosteroids before treatment with rituximab. IgG4-rich reactive lymphoid hyperplasia of the lacrimal gland is neither an established part of IgG4-related disease spectrum nor a known precursor lesion to lymphoma. Although there is a plausible risk of transforming to IgG4-related disease or to lymphoma, the biological potential and natural history of IgG4-rich reactive lymphoid hyperplasia remains to be determined.

The Expression of IgG and IgG4 in Orbital MALT Lymphoma: The Similarities and Differences of IgG4-Related Diseases

Objective

This study aims to study the expression and role of IgG and IgG4 in orbital MALT lymphoma and to compare the characteristics of IgG4-related diseases.

Patients and Methods

Patients with orbital MALT lymphoma, treated in the West China Hospital of Sichuan University from 2012 to 2017, were enrolled in the current study. The immunological examination of the wax blocks of orbital masses was performed again and the expression level of IgG and IgG4 in pathological tissue was analyzed.

Results

The results presented that the positive rates of IgG and IgG4 in the cases of orbital MALT lymphoma were 90.91% and 61.98% respectively, of which IgG4/IgG >40% accounted for 49.33%. The positive rates of IgG and IgG4 in relapse cases were 94.60% and 70.27% respectively, and IgG4/IgG >40% accounted for 42.31%. There was no significant change in the expression of IgG and IgG4 in cases of lymphoproliferation converting to MALT lymphoma whereas, in cases of MALT lymphoma postoperatively converting to lymphoproliferation, there was an increase in IgG and IgG4 expression, with the change of IgG4 being significant.

Conclusion

IgG and IgG4 have a high correlation in the pathogenesis of MALT lymphoma and may even play an important role in the transformation of MALT lymphoma into orbital lymphoid hyperplasia. Given the association of IgG4 with inflammation and tumors and as an important diagnostic indicator for IgG4-RD and IgG4-related ophthalmic diseases, IgG4 may play an important role in these diseases.

Immunoglobulin G4-related Disease

Immunoglobulin G4 (IgG4)-Related Disease (IgG4-RD) can cause fibroinflammatory lesions in nearly any organ and lead to organ dysfunction and irreversible damage. In addition to frequent involvement of the salivary glands, lacrimal glands, and/or pancreas, IgG4-RD often affects the chest. Thoracic manifestations include lung nodules and consolidations, pleural thickening, aortitis, and lymphadenopathy. The diagnosis is made after careful clinicopathologic correlation because there is no single diagnostic test with excellent sensitivity or specificity. Biopsy of pulmonary lesions can be useful for distinguishing IgG4-RD from common mimickers. Immunosuppressive regimens, such as glucocorticoids and/or glucocorticoid-sparing agents, form the cornerstone of treatment.

IgG4-related disease in a multi-ethnic community: clinical characteristics and association with malignancy

BACKGROUND

Immunoglobulin-G4-related disease (IgG4-RD) is a recently recognized fibro-inflammatory condition that can affect multiple organs. Despite growing interest in this condition, the natural history and management of IgG4-RD remain poorly understood.

AIM

To describe the clinical characteristics, treatment and outcomes of IgG4-RD in a multi-ethnic UK cohort, and investigate its possible association with malignancy.

DESIGN

Retrospective analysis of case-note and electronic data.

METHODS

Cases were identified from sub-specialty cohorts and a systematic search of an NHS trust histopathology database using 'IgG4' or 'inflammatory pseudotumour' as search terms. Electronic records, imaging and histopathology reports were reviewed.

RESULTS

In total, 66 identified cases of IgG4-RD showed a similar multi-ethnic spread to the local population of North West London. The median age was 59 years and 71% of patients were male. Presenting symptoms relating to mass effect of a lesion were present in 48% of cases and the mean number of organs involved was 2.4. Total of 10 patients had reported malignancies with 6 of these being haematological. 83% of those treated with steroids had good initial response; however, 50% had relapsing-remitting disease. Rituximab was administered in 11 cases and all achieved an initial serological response. Despite this, seven patients subsequently relapsed after a mean duration of 11 months and four progressed despite treatment.

CONCLUSIONS

We report a large UK-based cohort of IgG4-RD that shows no clear ethnic predisposition and a wide range of affected organs. We discuss the use of serum IgG4 concentrations as a disease marker in IgG4-RD, the association with malignant disease and outcomes according to differing treatment regimens.

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.

Lymphomas in IgG4-related disease: clinicopathologic features in a Western population

Lymphomas that occur in the setting of IgG4-related disease (IgG4-RD) are uncommon. Most reported cases derive from Asia and are MALT lymphomas occurring in orbital IgG4-RD. The spectrum of lymphomas among IgG4-RD patients in the Western world remains poorly defined. The aim of this study was to report our experience with lymphomas occurring in IgG4-RD. Eight cases were identified from the pathology and consultation files. The median age was 61 years (range 22-68) at IgG4-RD diagnosis and 63.5 years (range 33-79) at lymphoma diagnosis, with a M:F ratio of 4:4. The diagnosis of lymphoma and IgG4-RD was concurrent in three cases and asynchronous in five (interval 4.3-16.4 years). Concurrent cases included a MALT lymphoma and a diffuse large B cell lymphoma (DLBCL) occurring with IgG4-related sialadenitis and a follicular lymphoma occurring with orbital IgG4-RD. Asynchronous cases included a lymphoplasmacytic lymphoma with large cell transformation and intervening IgG4-related pancreatitis, a MALT lymphoma after lacrimal IgG4-RD, two DLBCLs after multiorgan IgG4-RD, and a DLBCL after IgG4-related sialadenitis. Our findings suggest that lymphomas in IgG4-RD are more varied in location and type than the experience reported from Asia to date. Pathologists should be aware of the potential for lymphoma to develop in patients with IgG4-RD and should have a high degree of suspicion when lymphadenopathy or extranodal masses persist despite appropriate therapy for IgG4-RD. The co-occurrence of IgG4-RD and lymphoma that is reported here and previously suggests a possible etiologic association.