Hashimoto's Thyroiditis with Increased IgG4-Positive Plasma Cells: Using Thyroid-Specific Diagnostic Criteria May Identify Early Phase IgG4 Thyroiditis

Utilizing Immunoglobulin G4 Immunohistochemistry for Risk Stratification in Patients with Papillary Thyroid Carcinoma Associated with Hashimoto Thyroiditis

BACKGRUOUND

Hashimoto thyroiditis (HT) is suspected to correlate with papillary thyroid carcinoma (PTC) development. While some HT cases exhibit histologic features of immunoglobulin G4 (IgG4)-related disease, the relationship of HT with PTC progression remains unestablished.

METHODS

This cross-sectional study included 426 adult patients with PTC (≥1 cm) undergoing thyroidectomy at an academic thyroid center. HT was identified based on its typical histologic features. IgG4 and IgG immunohistochemistry were performed. Wholeslide images of immunostained slides were digitalized. Positive plasma cells per 2 mm2 were counted using QuPath and a pre-trained deep learning model. The primary outcome was tumor structural recurrence post-surgery.

RESULTS

Among the 426 PTC patients, 79 were diagnosed with HT. With a 40% IgG4 positive/IgG plasma cell ratio as the threshold for diagnosing IgG4-related disease, a cutoff value of >150 IgG4 positive plasma cells per 2 mm2 was established. According to this criterion, 53% (43/79) of HT patients were classified as IgG4-related. The IgG4-related HT subgroup presented a more advanced cancer stage than the IgG4-non-related HT group (P=0.038). The median observation period was 109 months (range, 6 to 142). Initial assessment revealed 43 recurrence cases. Recurrence-free survival periods showed significant (P=0.023) differences, with patients with IgG4 non-related HT showing the longest period, followed by patients without HT and those with IgG4-related HT.

CONCLUSION

This study effectively stratified recurrence risk in PTC patients based on HT status and IgG4-related subtypes. These findings may contribute to better-informed treatment decisions and patient care strategies.

A machine learning-based diagnosis modeling of IgG4 Hashimoto's thyroiditis

PURPOSE

This study aims to develop a non-invasive diagnosis model using machine learning (ML) for identifying high-risk IgG4 Hashimoto's thyroiditis (HT) patients.

METHODS

A retrospective cohort of 93 HT patients and a prospective cohort of 179 HT patients were collected. According to the immunohistochemical and pathological results, the patients were divided into IgG4 HT group and non-IgG4 HT group. Serum TgAb IgG4 and TPOAb IgG4 were detected by ELISAs. A logistic regression model, support vector machine (SVM) and random forest (RF) were used to establish a clinical diagnosis model for IgG4 HT.

RESULTS

Among these 272 patients, 40 (14.7%) were diagnosed with IgG4 HT. Patients with IgG4 HT were younger than those with non-IgG4 HT (P < 0.05). Serum levels of TgAb IgG4 and TPOAb IgG4 in IgG4 HT group were significantly higher than those in non-IgG4 HT group (P < 0.05). There were no significant differences in gender, disease duration, goiter, preoperative thyroid function status, preoperative TgAb or TPOAb levels, and thyroid ultrasound characteristics between the two groups (all P > 0.05). The accuracy, sensitivity, and specificity were 57%, 78%, and 79% for logistic regression model of IgG4 HT, 80 ± 7%, 84.7% ± 2.6%, and 75.4% ± 9.6% for the RF model and 78 ± 5%, 89.8% ± 5.7%, and 64.7% ± 5.7% for the SVM model. The RF model works better than SVM. The area under the ROC curve of RF ranged 0.87 to 0.92.

CONCLUSION

A clinical diagnosis model for IgG4 HT established by RF model might help the early recognition of the high-risk patients of IgG4 HT.

Advancements in diagnosing IgG4-related disease of the head and neck: Navigating diagnostic pitfalls

IgG4-related disease (IgG4-RD) is an immune-mediated condition affecting nearly any organ. This review focuses on the nuances of diagnosing IgG4-RD affecting the head and neck. Salivary gland involvement, especially of the submandibular glands, often permits a definitive diagnosis on biopsy. However, elevated IgG4+ plasma cells are nonspecific and can be seen in chronic sialadenitis, lymphoma, and other mimics. Careful correlation of clinical and pathological findings is essential. Given the significant overlap with chronic sinusitis, IgG4-RD of the sinonasal region is difficult to diagnose histologically. Laryngeal and pharyngeal involvement appears rare as an isolated finding of IgG4-RD. Mastoid disease is uncommon and remains a diagnosis of exclusion. Thyroid manifestations pose challenges given unclear diagnostic criteria - Riedel's thyroiditis likely represents IgG4-RD, but the fibrosing variant of Hashimoto's thyroiditis as a form of the so-called 'IgG4-related thyroiditis' requires better characterisation. Eosinophilic angiocentric fibrosis, despite histologic similarities, only partially overlaps with IgG4-RD. This review aims to guide diagnosing IgG4-RD in the head and neck through a systematic, organ-focused discussion of the clinical context, the utility of immunostaining, histological mimics, and controversial issues that pose diagnostic pitfalls. Increased awareness of the nuances and difficulties diagnosing IgG4-RD affecting the head and neck will improve recognition of this protean disease.

Inflammatory and Infectious Disorders in Endocrine Pathology

A variety of inflammatory conditions may directly involve the endocrine glands, leading to endocrine dysfunction that can cause severe consequences on patients' health, if left untreated. Inflammation of the endocrine system may be caused by either infectious agents or other mechanisms, including autoimmune and other immune-mediated processes. Not infrequently, inflammatory and infectious diseases may appear as tumor-like lesions of endocrine organs and simulate neoplastic processes. These diseases may be clinically under-recognized and not infrequently the diagnosis is suggested on pathological samples. Thus, the pathologist should be aware of the basic principles of their pathogenesis, as well as of their morphological features, clinicopathological correlates, and differential diagnosis. Interestingly, several systemic inflammatory conditions show a peculiar tropism to the endocrine system as a whole. In turn, organ-specific inflammatory disorders are observed in endocrine glands. This review will focus on the morphological aspects and clinicopathological features of infectious diseases, autoimmune disorders, drug-induced inflammatory reactions, IgG4-related disease, and other inflammatory disorders involving the endocrine system. A mixed entity-based and organ-based approach will be used, with the aim to provide the practicing pathologist with a comprehensive and practical guide to the diagnosis of infectious and inflammatory disorders of the endocrine system.

Reshaping the Concept of Riedel's Thyroiditis into the Larger Frame of IgG4-Related Disease (Spectrum of IgG4-Related Thyroid Disease)

Recently, Riedel's thyroiditis (RT) was assimilated into the larger spectrum of immunoglobulin IgG4-related disease (IgG4-RD) in addition to a particular frame of IgG4-related thyroid disease (IgG4-RTD), underlying IgG4-RT, IgG4-associated Hashimoto's thyroiditis (and its fibrotic variant), and IgG4-related Graves's disease. Our objective was to overview recent data on RT, particularly IgG4-RD and IgG4-RTD. The case and study- sample analysis (2019-2023) included 293 articles and selected 18 original studies: nine single case reports (N = 9, female/male = 2/1, aged: 34-79 years, 5/9 patients with serum IgG4 available data, 2/5 with high serum IgG4) and four case series (N = 21; 4/5 series provided data on IgG4 profile, 3/21 had serum IgG4 assays, and 2/3 had abnormally high values). IgG4-RD and thyroid findings were analyzed in three cohorts (N = 25). Another two studies (N = 11) specifically addressed IgG4-RTD components. On presentation, the patients may have hypothyroidism, transitory thyrotoxicosis, goiter, long-term history of positive anti-thyroid antibodies, and hypoechoic ultrasound thyroid pattern. The 5-year analysis (N = 66) showed the rate of serum IgG4 evaluation remained low; normal values do not exclude RT. Mandatory histological and immunohistochemistry reports point out a high content of IgG4-carrying plasma cells and IgG4/IgG ratio. Unless clinically evident, histological confirmation provides a prompt indication of starting corticoid therapy since this is the first-line option. Surgery, if feasible, is selective (non-responders to medical therapy, emergency tracheal intervention, and open/core needle biopsy). Current open issues are identifying the role of serum IgG4 assays in patients with IgG4-RD, finding out if all cases of RT are IgG4-mediated, applying IgG4-RTD criteria of differentiation among four entities, and providing an RT/IgG4-RTD guideline from diagnosis to therapy. It remains that the central aim of approaching RT in daily practice is the early index of suspicion in order to select patients referred for further procedures that provide enough histological/immunohistochemistry material to confirm RT and its high IgG4 burden.

Immunohistochemistry in the pathologic diagnosis and management of thyroid neoplasms

The use of immunohistochemistry cannot be underestimated in the everyday practice of thyroid pathology. It has evolved over the years beyond the traditional confirmation of thyroid origin to molecular profiling and the prediction of clinical behavior. In addition, immunohistochemistry has served to implement changes in the current thyroid tumor classification scheme. It is prudent to perform a panel of immunostains, and the immunoprofile should be interpreted in light of the cytologic and architectural features. Immunohistochemistry can also be easily performed in the limited cellularity specimen preparation generated from thyroid fine-needle aspiration and core biopsy; however, it will require laboratory validation of immunostains specific to these preparations to avoid diagnostic pitfalls. This review discusses the application of immunohistochemistry in thyroid pathology with a focus on limited cellularity preparations.

Long-Term Exposure to Decabromodiphenyl Ether Promotes the Proliferation and Tumourigenesis of Papillary Thyroid Carcinoma by Inhibiting TRß

Simple Summary

PBDEs have been reported to have endocrine-disrupting and tumour-promoting activity; however, the effects of BDE209 (the highest brominated PBDEs) on the thyroid and the underlying mechanisms are unclear. In this study, we found that long-term exposure to BDE209 could cause chronic toxicity and potential tumourigenesis by inhibiting the expression and function of TRß, which induces the proliferation of thyroid tissue and the oncogenesis of thyroid carcinoma. These findings emphasize the damaging effects that exposure to BDE209 has on human thyroid and papillary thyroid carcinoma.

Abstract

Polybrominated diphenyl ethers (PBDEs) have been reported to possess endocrine-disrupting and tumour-promoting activity. However, the effects of long-term exposure to decabromodiphenyl ether (BDE209) on thyroid tumourigenesis of papillary thyroid carcinoma (PTC) and the underlying mechanisms remain poorly defined. In this study, functional assays in vitro and mouse models in vivo were used to evaluate the toxic effects of long-term exposure to environmental concentrations of BDE209 on the pathogenesis and progression of PTC. MTS, EdU and colony-forming assays confirmed the chronic toxicity of BDE209 on the proliferation of human normal follicular epithelial cell line (Nthy-ori 3-1) and PTC-derived cell lines (TPC-1 and BCPAP). Wound and Transwell assays showed that BDE209 exacerbated the aggressiveness of PTC cells. BDE209 significantly promoted cell proliferation during the S and G2/M phases of the cell cycle. Mechanistically, BDE209 altered the thyroid system by acting as a competitive inhibitor of thyroid receptor beta (TRß) expression and function, which was further proven by public databases and RNA-seq bioinformation analysis. Taken together, these results demonstrated that BDE209 has chronic toxicity and potential tumourigenic effects on the thyroid by inhibiting TRß.

Clinical differences between IgG4 Hashimoto's thyroiditis and primary thyroid lymphoma

Background

Hashimoto's thyroiditis (HT) can be divided into IgG4 HT and non-IgG4 HT based on IgG4 and IgG immunohistochemical staining. In clinical practice, it is often necessary to identify diseases such as primary thyroid lymphoma (PTL) and IgG4 HT when a patient presents with a rapidly enlarged thyroid. The aim of our study was to uncover the differential points between the two diseases.

Methods

Clinical information from 19 IgG4 HT and 10 PTL patients was obtained from the patients' medical records, including age, sex, main clinical manifestation, thyroid functional status, the presence of serum anti-thyroid peroxidase antibodies, anti-thyroglobulin antibodies, and thyroid ultrasonography results. Thyroid sections from all patients were collected to detect IgG4 and IgG expression by immunohistochemical staining.

Results

The IgG4 HT patients were significantly younger than those in the PTL group (39.68 ± 10.95 vs 66.20 ± 10.23 years, P < 0.001). There were no significant differences in the sex distribution or TgAb- or TPOAb-positive rates. The PTL group had a higher prevalence of clinical hypothyroidism than the IgG4 HT group (P = 0.016). In the PTL group, thyroid lesions were more likely to exhibit hypoechogenicity (6/6 vs 1/19, P < 0.001) on ultrasound images. In the PTL group, two patients met the immunohistochemical cut-off value of the criteria for IgG4 HT.

Conclusions

Simply relying on immunohistochemistry for IgG4 cannot diagnose IgG4 HT correctly when a patient presents with rapid thyroid enlargement. A combination of clinical and pathological analyses will help distinguish IgG4 HT from PTL which may be with abundant IgG4-positive plasma cells.

The characteristics and clinical significance of elevated serum IgG4/IgG levels in patients with Graves' disease

PURPOSE

This study aims to further explore the clinical and laboratory characteristics of patients with GD with high serum IgG4 based on the IgG4/IgG ratio.

METHODS

This study is a prospective observational study. A total of 25 normal controls and 84 people newly diagnosed with GD were enrolled in this study. Taking the IgG4/IgG ratio of 8% as the cutoff value, the experimental groups were further divided into two subgroups: the high IgG4/IgG subgroup and the normal IgG4/IgG subgroup. We evaluated the differences in clinical characteristics and laboratory parameters between the groups.

RESULTS

The IgG4, IgG4/IgG, and IL-17 of the newly diagnosed GD group were significantly higher than those of the normal control group (P < 0.05). The differences in age, IL-1β, IL-17, and eosinophil count between the high IgG4/IgG subgroup and the normal IgG4/IgG subgroup were statistically significant (P < 0.05). After ATD treatment, some patients developed allergies; the high IgG4/IgG subgroup was significantly higher than the normal IgG4/IgG subgroup (χ2 = 4.424, P = 0.035). After 3 months of ATD treatment in patients with GD, the TRAb in the normal IgG4/IgG subgroup were significantly lower than before (P < 0.05), while the difference in the high IgG4/IgG subgroup was not statistically significant (P > 0.05).

CONCLUSIONS

A small portion of patients with GD harbored elevated serum IgG4/IgG levels. They are younger, have higher eosinophils, and are more prone to allergies; also, they have higher levels of cytokines IL-1β and IL-17 and their remission is not easily attained after treatment with ATD; this could be due to the instability of the Th17/Treg cell balance.

Clinical features and treatment efficacy for IgG4-related thyroiditis

PURPOSE

This study aimed to clarify the clinical features of and evaluate the treatment efficacy for IgG4-related thyroiditis.

METHODS

Fourteen IgG4-related thyroiditis patients and 42 randomly matched IgG4-related disease (IgG4-RD) patients without thyroiditis in a prospective cohort at the Peking Union Medical College Hospital (PUMCH) were enrolled from 2011 to 2019. Patient demographics, clinical characteristics, laboratory parameters and treatment efficacy were analysed.

RESULTS

The prevalence of IgG4-related thyroiditis in our cohort was 2.0%. The average patient age was 42.8 ± 14.9 years, and the male: female ratio was 1:1. Goiter (14, 100.0%), hard thyroid (14, 100.0%) and neck compression (5, 35.7%) were the most prevalent onset symptoms observed. IgG4-related thyroiditis was characterized by asymmetric diffuse thyroid enlargement on ultrasound. Thirteen (92.9%) patients had hypothyroidism, and all patients had significantly elevated circulating thyroid antibodies. Compared with patients without thyroiditis, patients with IgG4-related thyroiditis had less submandibular gland involvement and lacrimal gland involvement and lower serum IgG4 and T-IgE levels (P = 0.019, P = 0.022, P = 0.004, and P = 0.006, respectively) and more single-organ involvement (P = 0.011). After treatment, the symptoms were relieved, while the size of the thyroid gland did not change significantly, and levothyroxine as a supplemental therapy was still needed.

CONCLUSIONS

IgG4-related thyroiditis is a distinct subtype of IgG4-RD characterized by positive circulating thyroid antibodies and a high rate of hypothyroidism. Although compression symptoms could be relieved with treatment, the thyroid size did not change significantly, and the damage to thyroid function was often irreversible.

Proposal of diagnostic criteria for IgG4-related thyroid disease

Patients with IgG4-related disease (IgG4-RD) are diagnosed in Japan by comprehensive or organ-specific diagnostic criteria. To date, organ-specific criteria have been established for several organs, but not for the thyroid. We attempted to establish diagnostic criteria for IgG4-related thyroid disease (IgG4-RTD) based on IgG4-RD research by The Research Program on Intractable Diseases from the Ministry of Health, Labour and Welfare of Japan. These criteria have been publicly reported to members of both the Japan Endocrine Society and the Japan Thyroid Association. Thyroid diseases associated with IgG4 include Hashimoto's thyroiditis, Graves' disease and Riedel's thyroiditis. As a comprehensive definition that includes both systematic and organ-specific forms, we use the broad term 'IgG4-related thyroid disease'. Diagnostic criteria for IgG4-RTD comprise the following five items: I) enlargement of the thyroid, II) hypoechoic lesions in the thyroid by ultrasonography, III) elevated serum IgG4 levels, IV) histopathological findings in the thyroid lesion (IgG4⁺ plasma cells >20/HPF and IgG4⁺/IgG⁺ plasma cell ratio >30%) and V) involvement of other organs. "Definitive" diagnosis of IgG4-RTD is made when I, II, III and IV are all fulfilled, while "probable" diagnosis of IgG4-RTD is when I, II, and IV or V are fulfilled. Patients who fulfill I, II and III criteria are considered as "possible" IgG4-RTD. We believe that the proposed diagnostic criteria contribute to more accurate diagnosis of IgG4-RTD as well as exclusion of mimicry. Furthermore, they may lead to better understanding of the clinical implications and underlying pathogenesis of IgG4-RTD.

IgG4 thyroiditis in the Asian population

Immunoglobulin G4-related disease (IgG4-RD) is an immune-mediated fibro-inflammatory condition that often causes the formation of tumefactive lesions. The discovery of IgG4-RD linked many well-known isolated conditions as a distinct multi-organ disease, and started an era of promoting investigation and treatment in relevant fields. In the thyroid gland, a subcategory of Hashimoto thyroiditis (HT) with IgG4-rich inflammation was first discovered and named IgG4 thyroiditis by our group. This subtype of HT presents with rapidly progressive clinical manifestations and destructive histopathological features underlying thyroid dysfunction, which are significantly different from the common type of HT. Moreover, other IgG4-rich thyroid conditions in patients with Graves' disease and systemic IgG4-RD have been described. These observations are most frequently reported in the Asian population for unknown reasons. Although recent studies demonstrated that IgG4 thyroiditis is a specific entity independent from IgG4-RD, recognition of this unique subset of thyroid disease has yielded important insights into understanding its pathogenesis and the development of novel therapeutic approaches.

IgG4-positive plasma cells in Hashimoto thyroiditis: IgG4-related disease or inflammation-related IgG4-positivity?

Despite the interest of researchers in IgG4-related disease (IgG4-RD), many questions still remain unanswered regarding the thyroid gland. We aimed to clarify the relationship between IgG4-positive plasma cells and the histopathological pattern in the Hashimoto thyroiditis (HT) in a Finnish series. HT specimens (n = 280) were retrieved from the Department of Pathology, Fimlab Laboratories. After re-evaluation, 82 (29%) cases (72 females and 10 males, 52 ± 17 years) with significant fibrosis were selected. CD38, IgG and IgG4 positivity in plasma cells was evaluated by immunohistochemistry. Adjusted IgG4-positive plasma cells per HPF > 20 and IgG4- to IgG-positive plasma cell ratio > 30% were adopted as threshold criteria and related to other morphological features. IgG4-positive HT group included 13 cases (15% from fibrotic HT, 4.6% from all HT, 50 ± 15 years, 11 females) with adjusted HPF count 30 ± 5 (23-40) IgG4-positive cells. IgG4-positivity significantly correlated with the presence of lobulation, oncocytic metaplasia and certain type of fibrosis, fibrosis spread outside the gland, lymphocytes/plasma cells epithelial penetration, the predominance of microfollicles and follicular atrophy in the present study. Despite the persisting uncertainty whether HT is IgG4-RD, HT with IgG4-positive plasma cells is histopathologically distinct entity with some geographic variability.