Hashimoto's thyroiditis with elevated serum IgG4 concentrations is not equivalent to IgG4 Hashimoto's 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.

IgG4-positive Hashimoto thyroiditis and its association with IgG4-related sclerosing disease

A woman in her 50s was referred with suspected thyroid malignancy and underwent total thyroidectomy. Immunohistochemical analysis revealed IgG4-positive Hashimoto's thyroiditis. IgG4-related thyroid disease is poorly understood, and thought to encompass various entities including IgG4-positive Hashimoto's thyroiditis, Fibrosing Variant of Hashimoto's thyroiditis, Reidel's thyroiditis and Graves' disease with elevated IgG4 levels. Furthermore, it may be associated with a systemic fibrosing condition called 'IgG4-related sclerosing disease'. The clinical significance of IgG4-positive thyroid disease, however, remains unclear.

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.

IgG4 immunohistochemistry in Riedel's thyroiditis and the recommended criteria for diagnosis: A case series and literature review

OBJECTIVE

Riedel's thyroiditis (RT) is a very rare chronic fibrosing thyroiditis that is often associated with multifocal fibrosclerosis. Although the relationship of RT and IgG4-related disease (IgG4-RD) has been suggested, the expression of IgG and IgG4 in thyroid tissues of patients with RT has seldom been studied.

DESIGN

A case series and literature review.

PATIENTS AND MEASUREMENTS

We searched our hospital's pathology database and identified five cases of RT between 2000 and 2019. The expression levels of IgG4 and IgG in thyroid tissues were detected by immunohistochemistry. We also performed a literature search of the electronic databases PubMed/MEDLINE, Web of Science and China National Knowledge Internet (CNKI). Eight papers were included in this study.

RESULTS

According to immunohistochemistry, the numbers of IgG4+ plasma cells per high-power field (HPF) of the five RT patients at our hospital were 80, 8, 50, 10 and 22, and the respective IgG4+/IgG+ ratios were 76%, 80%, 43%, 19% and 28%. In the literature, 15 RT patients with confirmed IgG4 and IgG immunohistochemical findings were identified. Only seven of them fulfilled the IgG4-RD diagnostic criteria in terms of immunohistochemistry (IgG4+ > 10/HPF, IgG4+/IgG+ > 40%). In order to ensure that most RT cases can meet the IgG4 immunohistochemical criteria, an organ-specific cut-off value (≥10 IgG4+ plasma cells/HPF and ≥ an IgG4+/IgG ratio of 20%) was finally selected in our study.

CONCLUSION

Our findings of IgG4 expression in patients with RT suggest that a cut-off of 10 IgG4+ plasma cells/HPF and an IgG4+/IgG ratio of 20% are more suitable diagnostic criteria for RT in IgG4-RD.