Usefulness of core needle biopsy of thyroid for the diagnosis of IgG4 Hashimoto's thyroiditis

IgG4-related Hashimoto's thyroiditis (IgG4 HT) is characterized by rapid progression and may be associated with an increased risk of papillary thyroid carcinoma (PTC). The diagnosis of IgG4 HT relies primarily on postoperative pathological analysis. Early identification of IgG4 HT is crucial for guiding patient management. This study assessed the possibility of thyroid core needle biopsy (CNB) in diagnosing IgG4 HT.

One hundred and twenty HT patients who underwent color Doppler-guided CNB and subsequent thyroid surgery were collected in Peking University First Hospital. Clinical, serological, sonographic, and histopathological features were also collected. The numbers of IgG4 and IgG plasma cells were counted in five high power fields (HPF), then the average numbers of IgG4+ and IgG+ plasma cells per HPF were calculated respectively.

Based on the IgG4 and IgG immunohistochemistry results of 120 surgical specimens, cases were subclassified as IgG4 HT (n = 18) and non-IgG4 HT (n = 102) groups by the thyroid-specific diagnostic criteria (IgG4+ plasma cells > 20/HPF and IgG4+/IgG+ plasma cell ratio > 30%). CNB samples from IgG4 HT patients were subsequently subjected to IgG4/IgG immunostaining. However, only eight of the corresponding CNB tissues met the IgG4 HT diagnostic criteria. The remaining ten patients had IgG4+ positivity ranged in 10-20 cells/HPF and an IgG4+/IgG+ plasma cell ratio ranging from 20% to 67%. Histopathological characteristics of thyroid tissue were consistent between the surgical and CNB samples.

IgG4/IgG immunostaining of CNB samples derived from thyroid tissue may serve as a valuable tool for supporting the diagnosis of IgG4 HT.